How does high DHA fish oil affect health? A systematic review of evidence

Figures & data

Figure 1. Summary and types of all studies retrieved, selected and used for the present analysis of high DHA fish oils (number of studies and percentage relative to entire dataset).

Figure 2. Number, and percentage relative to entire dataset, of retrieved and analysed studies per age classes used for the present analysis of high DHA fish oils.

Figure 3. The physiological/medical application areas of human studies retrieved and used for the present analysis of high DHA fish oils (number of studies and percentage relative to human studies).

Figure 4. The physiological/medical application areas of animal studies retrieved and used for the present analysis of high DHA fish oils (number of studies and percentage relative to animal studies).

Figure 5. The physiological/medical application areas of follow-up studies retrieved and used for the present analysis of high DHA fish oils (number of studies and percentage relative to follow-up studies).

Table 1. A summary of experimental design and results from human studies testing the effects of high DHA fish oil on heart functioning and exercise performance.

Reference & Journal	Aim of study	Type of study	Number of participants / Test formulation	Age range (years)	DHA: EPA	Results / Conclusion	Outcome	Fish oil supplier
(Hill et al. 2007a)	To examine the individual and combined effects of n-3 FA supplements and regular exercise on body composition and cardiovascular health.	A randomized trial.	81 overweight men and women with high blood pressure, cholesterol, or TAG were randomly assigned to 4 groups. Two groups took 6× 1 g tuna fish oil (1.56 g DHA + 0.36 g EPA) per day and 2 groups took 6× 1 g sunflower oil per day, over 12 weeks. One of the groups assigned to each oil treatment also exercised regularly.	25–65	4.3: 1	Fish oil supplementation lowered TAG, increased HDL cholesterol and improved endothelium-dependent arterial vasodilation. Exercise improved arterial compliance. Both fish oil and exercise independently reduced body fat.	+	Nu-Mega Ingredients (Clover), Australia
The American Journal of Clinical Nutrition
(O'Keefe Jr et al. 2006)	To explore some of the possible mechanisms by which relatively low doses of n-3 fatty acids could decrease the risk of sudden cardiac death.	A randomized, double-blind, placebo-controlled, crossover trial.	18 males with a history of myocardial infarctions received either a placebo or an n-3 fatty acid supplement (0.58 g DHA + 0.22 g EPA), taken 3 times a day for two sequential 4-month periods.	67.8 ± 6.5	2.6: 1	High DHA fish oil decreased HR at rest from 73 ± 13 to 68 ± 13 beats/min and improved 1-minute HR recovery after exercise. Though HRV in the high-frequency band increased (p <0.02), overall HRV was unaffected by the n-3 group.	No effect+	Ocean Nutrition Canada, Ltd., Canada
The American Journal of Cardiology
(Buckley et al. 2009)	To test whether supplementation with high DHA fish oil could improve endurance exercise performance, recovery, or CV responses to exercise.	A randomized double-blind, placebo-controlled, parallel matched-pairs design.	25 male Australian Rules football players randomly received either 6 g/d of high DHA fish oil (1.56 g DHA + 0.36 g EPA) or sunflower oil (placebo) during 5 weeks of training. Gender not specified.	Not specified	4.3: 1	Supplementation with fish oil improved CV function and reduced CV risk factors after 5 weeks, but did not improve endurance performance or recovery in elite Australian Rules footballers.	+	Nu-Mega Ingredients (Clover), Australia
Journal of Science & Medicine in Sport
(Ninio et al. 2008)	To determine whether fish oil supplementation improves HRV, a predictor of cardiac death.	A randomized, double-blind, parallel trial.	65 overweight men and women consumed 6 g/d of fish oil (DHA 1.56 g + EPA 0.36 g) or sunflower-seed oil (placebo) for 12 weeks with/without moderate physical activity.	25–65	4.3: 1	Fish oil supplementation improved HRV by increasing high-frequency power. It also reduced HR at rest and during submaximal exercise.	+	Nu-Mega Ingredients (Clover), Australia
British Journal of Nutrition
(Peoples et al. 2008)	To test the effects of fish oil supplementation on O2 consumption during exercise.	A double-blind, parallel design.	16 well-trained, male cyclists, randomly assigned to groups, consumed capsules containing 1 g olive oil (control) or fish oil (2.4 g DHA + 0.8 g EPA/day), 8 times a day for 8 weeks.	21–30	3.0: 1	No difference in O2 consumption or peak workload was observed after supplementation with fish oil.	No effect	Nu-Mega Ingredients (Clover), Australia
Journal of Cardiovascular Pharmacology						Fish oil supplementation lowered steady-state submaximal exercise heart rate, whole-body O2 consumption, and rate pressure product.	+
(Armah et al. 2008)	To examine the impact of fish oil fatty acids, added to a standard test meal, on postprandial vascular reactivity.	A single-blind crossover trial.	25 healthy males received, at random, either a placebo oil meal (40 g placebo oil) or a fish oil meal (31 g placebo oil + 9 g fish oil, providing 3.2 g DHA + 2.2 g EPA) on two occasions, separated by one week.	46 (average)	1.5: 1	Fish oils significantly improved postprandial endothelium-independent vasodilation.	+	Ocean Nutrition Canada, Ltd., Canada
Clinical Science
(Chong et al. 2010)	To investigate the acute effects of a n-3 LC-PUFA rich meal on measures of arterial stiffness.	A postprandial single-blind, randomized, controlled crossover study.	25 healthy men and women received either a control meal or a n-3 LC-PUFA rich meal (23.2 g of control oil and 6.8 g fish oil, providing 2.0 g EPA + 2.7 g DHA) on two occasions, in a random order.	19–68	1.3: 1	Consumption of the n-3 LC-PUFA rich meal had an attenuating effect on augmentation index and stiffness index compared with the control meal.	+	Croda Europe Ltd, United Kingdom
Clinical Nutrition
(McManus et al. 2016)	To investigate the impact of EPA versus DHA on arterial stiffness and reactivity, and the underlying mechanisms (focusing on plasma oxylipins), in the postprandial state.	Three-arm, crossover, acute test meal trial.	26 males with an increased CVD risk received a high-fat test meal containing either high EPA fish oil (0.68 g DHA + 4.16 g EPA), high DHA fish oil (4.16 g DHA + 0.81 g EPA) or control oil.	35–55	5.1: 1	A single dose of DHA significantly improved postprandial arterial stiffness.	+	Epax, FMC Health and Nutrition, Norway
Journal of Lipid Research
(McEwen et al. 2013)Seminars in Thrombosis and Hemostasis	To investigate the effects of n-3 LC-PUFA on platelet function in healthy subjects and subjects with CVD.	A randomized study.	40 healthy men and women, and 16 with CVD, received n-3 LC-PUFA (0.52 g DHA + 0.12 g EPA/day) for 4 weeks. No placebo test group.	Healthy subjects: 21–64	4.3: 1	In healthy subjects, n-3 LC-PUFA significantly reduced adenosine diphosphate (ADP)–induced and adrenaline-induced platelet aggregation. n-3 LC-PUFA also reduced P-selectin expression on platelets and platelet–monocyte aggregates after activation with ADP 0.5 µM. There were fewer changes in platelet aggregation and activation found in subjects with CVD.	+	Nu-Mega Ingredients (Clover), Australia
				Subjects with CVD: 50–83
(McEwen et al. 2015)	To investigate the effects of n-3 on novel markers of global coagulation (the generation of fibrin and thrombin) in healthy subjects and subjects with CVD.	A randomized study.	40 healthy men and women, and 16 with CVD, received 0.52 g DHA + 0.12 g EPA per day for 4 weeks. No placebo test group.	21–64	4.3: 1	In subjects with CVD, the high DHA preparation reduced the fibrin generation parameter of overall haemostasis potential, a more global summary of coagulation, but did not affect fibrinolysis.	+	Nu-Mega Ingredients (Clover), Australia
Seminars in Thrombosis and Hemostasis							No effect
(Macartney et al. 2014)	To test the effect of low-dose fish oil supplementation on HR response to intense exercise and recovery in physically fit males.	A double-blind, parallel design.	26 healthy males consumed either 2× 1 g soya bean oil (control) or tuna fish oil (0.56 g DHA +0.14 g EPA) per day for 8 weeks.	18–40	4.0: 1	Peak HR was not affected by supplementation with fish oil, however, during submaximal exercise over 5 min, fewer total heart beats were recorded in the fish oil group compared to the control group. Supine HR recovery (half-time) after cycling was significantly faster after fish oil supplementation.	+	Nu-Mega Ingredients (Clover), Australia
British Journal of Nutrition
(Poppitt et al. 2009)	To test whether treatment with a guideline-recommended moderate-dose fish oil supplement could improve cardiovascular biomarkers, mood- and health-related quality of life in patients with ischemic stroke.	A randomized, double-blind trial.	102 overweight men and women with CT-confirmed stroke were randomized to groups receiving either 3 g/d of placebo oil or fish oil (0.7 g DHA + 0.3 g EPA) for 12 weeks.	>45	2.3: 1	There was no effect on cardiovascular biomarkers or mood in patients with ischemic stroke following 12 weeks of treatment with a moderate-dose fish oil supplement.	No effect	Sea Dragon, New Zealand
Stroke
(Mann et al. 2010)	To test and compare the effects of seal oil (DPA) and tuna fish oil (low DPA, 40% less EPA and double the DHA of seal oil) on blood lipids and platelet factors in healthy volunteers.	A randomized, parallel, double-blind, placebo-controlled, clinical trial.	30 men and women consumed, in capsule form, 1 g/d of either seal oil (0.45 g DHA + 0.34 g EPA + 0.23 g DPA), fish oil (0.81 g DHA + 0.21 g EPA + 0.030 g DPA) or sunola oil (placebo), for 2 weeks.	20–50	3.8: 1	Seal oil may be more efficient than fish oil at promoting healthy plasma lipid profiles and lowering thrombotic risk, possibly due to its high DPA and EPA content.	No effect	Nu-Mega Ingredients (Clover), Australia
Lipid
(Phang et al. 2013)	To determine whether there is a gender bias on platelet aggregation during long-term n-3 LC-PUFA supplementation.	A double-blind, randomized, placebo-controlled trial.	94 healthy men and women, assigned into groups at random, consumed sunola oil (placebo), EPA-rich fish oil (0.2 g DHA + 1 g EPA) or DHA-rich fish oil (1 g DHA + 0.2 g EPA) for 4 weeks.	40 (mean)	5.0: 1	Males are more likely to benefit from supplementation with EPA, whereas females are more responsive to DHA.	+	EPAX 1050 TG/N, Norway
Journal of Nutrition
(Khan et al. 2003)	To evaluate the effects of dietary achievable supplementation of n-3 and n-6 fatty acids on microvascular blood flow and endothelial function in healthy subjects.	A double-blind, randomized, placebo-controlled study.	173 healthy men and women took 5 g/day of an oil supplement for 8 months. Supplements included either placebo oil, oleic acid-rich sunflower oil, evening primrose oil, soya bean oil, tuna fish oil (6% EPA + 27% DHA) or tuna/evening primrose oil mix.	45–61	4.5: 1	Fish oil supplementation has a beneficial effect on endothelial function, even in normal healthy subjects.	+	Not specified
Cardiovascular Research
(Ottestad et al. 2012)	To investigate the effect of fish oil supplementation on the plasma lipidomic profile in healthy subjects.	A double-blind, randomized, controlled, parallel-group study.	37 healthy men and women consumed a capsule containing either 8 g of oleic acid-rich sunflower oil or 8 g fish oil (0.9 g DHA + 0.7 g EPA) per day for 7 weeks.	18–50	1.3: 1	In healthy subjects, fish oil supplementation alters lipid metabolism which increases the proportion of phospholipids and TAGs containing long-chain polyunsaturated fatty acids.	+	TINE SA, Norway
Plos One
(Kumar et al. 2011)	To investigate the effects of chronic fish oil supplementation on human pulmonary vein (PV) and left atrial electrophysiology in paroxysmal atrial fibrillation (PAF).	A randomized trial.	36 males with PAF were randomized into a control group or a fish oil group (6 g/d of fish oil, providing 1.5 g DHA + 0.3 g EPA) for a mean of 40±12 days.	18–75	5.0: 1	Patients with PAF chronically supplemented with fish oil exhibited distinctive electrophysiologic properties including prolonged pulmonary venous and left atrial ERPs, and decreased susceptibility to initiation AF from within PVs.	+	Nu-Mega Ingredients (Clover), Australia
American Journal of Cardiology
(Pedersen et al. 2010)	To investigate the effect of fish oil on body composition and cardiovascular risk markers in boys during the pubertal growth spurt.	A randomized trial.	78 healthy, but slightly overweight, boys received bread containing high DHA fish oil (0.90 g DHA + 0.2 g EPA) or vegetable oil (placebo). 3 pieces of bread were consumed per day for 16 weeks.	13–15	4.6: 1 ^*	Fish oil improves blood pressure in normotensive and normolipidemic adolescent boys that are slightly overweight.	+	Nu-Mega Ingredients (Clover), Australia
The Journal of Pediatrics
(Buckley et al. 2004)	To establish the differential impact of EPA and DHA on plasma lipids and apolipoprotein B in adults.	A double-blind, placebo-controlled, parallel study.	42 healthy men and women were randomized to control oil, EPA-rich fish oil (0.7 g DHA + 4.8 g EPA/day), or DHA-rich fish oil (4.9 g DHA + 0.81 g EPA/day) for 4 weeks.	20–70	6.1: 1	DHA may be more efficacious than EPA in improving the plasma lipid profile.	No effect	Ocean Nutrition Canada, Ltd., Canada
British Journal of Nutrition
(Krebs et al. 2006)International Journal of Obesity	To test whether the addition of n-3 LC-PUFA to a low fat, high carbohydrate weight-loss programme results in greater improvements in inflammation, insulin sensitivity and CVD risk, other than weight-loss alone.	A randomized, double-blind trial.	93 overweight, insulin-resistant females (BMI >27kg/m^2) were randomized to groups consuming, in capsule form, 5× 1 g of either fish oil (2.9 g DHA + 1.3 g EPA) or placebo oil per day for 12 weeks.	21–69	2.2: 1	Relative to the control group, TAG and adipose tissue were significantly lower and higher, respectively, in the high DHA fish oil group at 24 weeks, but not for LDL cholesterol, total cholesterol, systolic or diastolic blood pressure.	No effect+	Pronova, Norway
(Sjoberg et al. 2010)British Journal of Nutrition	To investigate the dose–response effects of n-3 LC-PUFA on HR and HRV to better understand its effects and benefits.	A randomized, double-blind, placebo-controlled study.	67 overweight or obese men and women were randomly allocated to consume either 6 g/d of sunola oil (placebo), or fish oil (0.26 g DHA + 0.06 g EPA per g) at doses of 2, 4 or 6 g/d for 12 weeks.	52 (mean)	4.3: 1	Fish oil supplementation had no effect of on blood pressure, small artery compliance or HR. However, the low to high frequency ratio of HRV decreased with increasing doses of fish oil.	No effect+	Nu-Mega Ingredients (Clover), Australia
(Finnegan et al. 2003)	To compare the effects of increased dietary intakes of ALA and EPA + DHA on a range of atherogenic risk factors.	A double-blind, placebo-controlled, parallel study.	150 moderately hyperlipidemic men and women were randomized into five groups, receiving either a n-6 control, 0.28 g DHA + 0.18 g EPA, 0.76 g DHA + 0.49 g EPA, 3.7 g ALA or 8.7 g ALA per day, for 6 months.	25–72	1.5: 1	Long-term consumption of modest amounts of dietary ALA does not reproduce the effects of preformed EPA + DHA on TAG concentrations, tissue DHA concentrations, or in vitro susceptibility to oxidation of LDL.	No effect	Roche Vitamins Ltd, Switzerland
American Journal of Clinical Nutrition
(Caslake et al. 2008)	To determine the effect of moderate EPA and DHA intakes on the plasma fatty acid profile, lipid and apolipoprotein concentrations, lipoprotein subclass distribution, and markers of oxidative status.	A double-blind, placebo-controlled, dose-response, crossover study.	312 men and women consumed capsules containing control oil or fish oil (either 0.57 g DHA + 0.13 g EPA or 1.48 g DHA + 0.32 g EPA), in random order, over an 8-week duration.	20–70	1.4: 1	Supplements providing EPA + DHA at doses as low as 0.7 g/day have a significant effect on the plasma lipid profile.	+	Ocean Nutrition Canada, Ltd., Canada
American Journal of Clinical Nutrition
(Milte et al. 2008)	To test a dose-response relationship between moderate levels of high DHA fish oil and changes in both erythrocyte DHA content and blood lipids.	A randomized, double-blind, placebo-controlled, parallel study.	67 men and women consumed 2, 4 or 6 g/d of high DHA fish oil (0.52 g DHA + 0.12 g EPA), or a placebo, for 12 weeks.	53 (mean)	4.3: 1	For every 1 g increase in DHA intake per day, there was a 23% reduction in TAG, 4·4% increase in HDL cholesterol and 7·1% increase in LDL cholesterol.	+	Nu-Mega Ingredients (Clover), Australia
British Journal of Nutrition

* Personal communication; the DHA: EPA ratio was not specified in the published paper, but was provided by authors of the study upon request.

Table 2. A summary of experimental design and results from human studies testing the effects of high DHA fish oil on the brain and visual system.

Reference & Journal	Aim of study	Type of study	Number of participants / Test formulation	Age range (years)	DHA: EPA	Results / Conclusion	Outcome	Fish oil supplier
(Hirayama et al., 2004) European Journal of Clinical Nutrition	To investigate whether docosahexaenoic acid (DHA) supplementation could ameliorate attention-deficit/ hyperactivity disorder (AD/HD) symptoms in AD/HD children.	A placebo-controlled, double-blind study.	40 AD/HD (including eight AD/HD-suspected) boys and girls were randomized to groups receiving either high DHA fish oil (3.60 g DHA + 0.70 g EPA/week) or olive oil (placebo) for 2 months.	6-12	5.1: 1	DHA supplementation did not improve AD/HD-related symptoms.	No effect	Not specified
(Itomura et al., 2005) Journal of Nutritional Biochemistry	To investigate whether fish oil supplementation affected Japanese schoolchildren's behaviour, with changes in aggression over time as the primary endpoint.	A randomized, double-blind, placebo-controlled trial.	166 boys and girls were randomized to receive control supplements or fish oil (3.60 g DHA + 0.84 g EPA/week) for 3 months.	9-12	4.3: 1	Physical aggression might be affected by fatty acid nutrition, especially in girls. There were no significant changes in physical aggression in boys.	No effect +	Not specified
(Freund-Levi et al., 2008) International Journal of Geriatric Psychiatry	To determine effects of dietary n-3 supplementation to AD patients with a mild to moderate disease on psychiatric and behavioral symptoms, daily functions and a possible relation to APOEgenotype.	A randomized, double-blind, placebo-controlled, clinical trial.	204 AD men and women were randomized into groups consuming placebo oil (1 g/d of corn oil, including 0.6 g of linoleic acid) or 4 fish oil (1.72 g DHA + 0.60 g EPA/day) for 6 months.	74 (mean)	2.8: 1	Supplementation with n-3 in patients with mild to moderate AD did not result in marked effects on neuropsychiatric symptoms, except for possible positive effects on depressive symptoms in non-APOEv4 carriers and agitation symptoms in APOEv4 carriers.	No effect	Pronova Biocare A/S, Norway
(Hamazaki et al., 2008) Asia Pacific Journal of clinical nutrition	To observe the effects of fish oil on behavior and school attendance rates in school children.	A randomized, double-blind, placebo-controlled, clinical trial.	233 fourth to sixth year school boys and girls were randomized into groups receiving soybean oil (placebo) or fish oil (containing 0.65 g DHA + 0.10 g EPA/day) for 3 months.	9-12	6.5: 1	There were no differences in behaviour between groups, however, children in the DHA group had a significantly higher attendance rate.	No effect +	Not specified
(van Goor et al., 2010) British Journal of Nutrition	To test whether supplementation of DHA during pregnancy and lactation influences the infant's brain development and whether additional 20:4n-6 modulates this effect.	A double-blind, placebo-controlled, randomized trial from about week 17 (range 14–20 weeks) of pregnancy until 12 weeks postpartum.	183 healthy females were randomized into groups receiving either a control, DHA (0.22 g DHA + 0.03 g EPA) or DHA + 20:4n-6 (0.22 g 20:4n-6 + 0.22 g DHA + 0.04 g EPA).	32-33 (mean)	6.1: 1	Neither DHA alone nor DHA + 20:4n-6 influenced outcomes in the traditional examination. General movement quality of infants in the DHA group was lower than that of infants in the other two groups.	No effect −	Marinol D40, Lipid Nutrition B.V., The Netherlands
(Makrides et al., 2010) The Journal of the American Medical Association	To determine whether increasing DHA during the last half of pregnancy will result in fewer women with high levels of depressive symptoms and enhance the neurodevelopmental outcome of their children.	A double-blind, multicenter, randomized controlled trial (DOMInO trial).	2399 pregnant women who were less than 21 weeks’ gestation were randomized into groups and consumed, in capsule form, either vegetable oil without DHA, or high DHA fish oil (0.80 g DHA + 0.10 g EPA/day), for ∼10 weeks.	28.9 (mean)	8.0: 1	The use of high DHA fish oil capsules compared with vegetable oil capsules during pregnancy did not result in lower levels of postpartum depression in mothers or improved cognitive and language development in their offspring during early childhood.	No effect	Incromega 500 TG, Croda Chemicals, England
(Dangour et al., 2010) American Journal of Clinical Nutrition	To test if n-3 LC-PUFA supplementation would benefit cognitive function in cognitively healthy older people.	A randomized, double-blind, controlled trial.	867 cognitively healthy men and women were randomized to olive oil or fish oil (0.50 g DHA + 0.20 g EPA/day) capsules for 24 months.	70-79	2.5: 1	There was no change in cognitive function scores over 24 months, and intention-to-treat analysis showed no significant differences between trial arms at 24 months in the verbal learning test or any secondary cognitive outcome.	No effect	Ocean Nutrition Canada Ltd, Canada
(Jackson et al., 2012a) British Journal of Nutrition	To examine the effects of 12 weeks’ dietary supplementation with high DHA fish oil or high EPA fish oil on cognitive function.	A double-blind, placebo-controlled, randomized trial.	159 healthy young men and women were randomized to either 1 g/d of olive oil (placebo), high DHA fish oil (0.45 g DHA + 0.09 g EPA) or EPA-rich fish oil (0.20 g DHA + 0.30 g EPA) for 12 weeks.	18-35	5.0: 1	Dietary supplementation with n-3 LC-PUFA in healthy, normally developing, and impairment-free populations is unlikely to result in cognitive enhancement.	No effect	EPAX AS (Aalesund, Norway)
(Jackson et al., 2012b) British Journal of Nutrition	To investigate any treatment-related effects of supplementation with DHA- and EPA-rich fish oil in healthy volunteers on the cerebral haemodynamic response to cognitive tasks in the prefrontal cortex.	A double-blind, placebo-controlled trial.	22 healthy men and women were randomized to either 1 g/d placebo oil (olive oil), high DHA fish oil (0.45 g DHA + 0.09 EPA) or EPA-rich fish oil (0.20 g DHA + 0.30 g EPA) for 12 weeks.	22 (mean)	5.0: 1	Supplementation with high DHA fish oil, in comparison with the placebo, resulted in a significant increase in the concentrations of oxy-Hb and total levels of Hb, indicative of increased cerebral blood flow (CBF), during the cognitive tasks. In comparison, no effect on CBF was observed following supplementation with EPA-rich fish oil.	+	EPAX AS (Aalesund, Norway)
(Stough et al., 2012) Neurobiology of Aging	To test the effects of supplementation with DHA on cognitive function and visual acuity in a healthy aging population.	A triple-blind, placebo-controlled, randomized, repeated-measures trial.	74 healthy men and women received either 1g of tuna oil (0.252 g DHA + 0.06 g EPA) or soybean oil (placebo) for 3 months.	45-77	4.2: 1	DHA supplementation had no significant effects on cognitive functioning. For participants with corrected vision, the group receiving DHA were found to have significantly better right eye visual acuity post-treatment in comparison with the control.	Brain: No effect Eye: +	Nu-Mega Ingredients (Clover), Australia
(Meldrum et al., 2012) British Journal of Nutrition	To test the effects of direct supplementation with high dose fish oil on infant neurodevelopmental outcomes and language.	A randomized, double-blind, placebo-controlled trial.	420 healthy term boys and girls were assigned to receive a DHA-rich fish oil supplement (0.25 g DHA + 0.06 g EPA/day) or a placebo (olive oil) from birth to 6 months.	Infants; 0–6 months	4.2: 1	The results suggest that improved postnatal n-3 LC-PUFA intake in the first 6 months of life using high dose infant fish oil supplementation was not beneficial to global infant neurodevelopment. However, some indication of benefits to early communicative development was observed.	No effect +	Nu-Mega Ingredients (Clover), Australia
(Barbadoro et al., 2013) Molecular Nutrition & Food Research	To evaluate the effects of 3-week supplementation with EPA and DHA on perceived stress/anxiety and hypothalamic-pituitary-adrenocortical activity.	A randomized, double-blind, placebo-controlled trial.	31 male alcoholics undergoing a residential rehabilitation program were randomized to placebo (1 capsule/day containing microcrystalline cellulose powder) or fish oil (0.25 g DHA + 0.06 g EPA) for 3 weeks.	>18	4.2: 1	An elevated n-3 intake may reduce distress symptoms and basal cortisol secretion in abstinent alcoholics.	+	FX s.r.l. by SALIX s.r.l., Italy
(Hurtado et al., 2015) Journal of Pediatric Gastroenterology and Nutrition	To elucidate (1) whether a dairy drink enriched with n-3 LC-PUFA could have an impact on the lipid profile of the mother and the newborn, and (2) whether this intervention could affect the newborns’ visual and cognitive development.	A randomized, double-blind, controlled trial.	110 pregnant women were randomized into a control (400 mL/d control dairy drink) or supplemented group (400 mL/d fish-oil enriched dairy drink, providing 0.32 g DHA + 0.07 g EPA/day) for ∼7 months.	30 (mean)	4.4: 1	Dietary supplementation with n-3 LC-PUFA during pregnancy did not have effects on visual and cognitive/psychomotor development.	No effect	Not specified
(Bradbury et al., 2004) Nutrition Journal	To investigate whether perceived stress is ameliorated by DHA in stressed university staff.	A small intervention study nested within a larger prospective cross-sectional study.	30 men and women that scored ≥ 17 on the Perceived Stress Scale were randomized to olive oil (placebo) or fish oil (6 capsules/day containing 1.51 g DHA + 0.36 g EPA) for 6 weeks.	18-60	4.2: 1	As a pilot study, it was not sufficiently powered to find any significant difference between the fish oil group and the placebo group.	No effect	Not specified
(Smithers et al., 2008) The American Journal of Clinical Nutrition	To test visual responses of preterm infants fed human milk and formula with a DHA concentration estimated to match the intrauterine accretion rate (high-DHA group), compared with infants fed human milk and formula containing DHA at current concentrations.	A double-blind, randomized, controlled trial.	143 Preterm boys and girls born at <33 weeks gestation were fed either human milk or formula containing 1% DHA (high-DHA group) or ∼0.3% DHA (control group) for 4 months until reaching their estimated due date.	Preterm infants	4.5: 1	At 2 months corrected age, acuity of the high-DHA group did not differ from the control group. By 4 months’ corrected age, the high-DHA group exhibited an acuity that was 1.4 cycles per degree higher than the control group. Authors concluded that the DHA requirement of preterm infants may be higher than currently provided by preterm formula or human milk of Australian women.	+	Nu-Mega Ingredients (Clover), Australia
(Makrides et al., 2009) The Journal of the American Medical Association	To test the effect of meeting the estimated DHA requirement of preterm infants on neurodevelopment.	A double-blind, randomized, controlled trial.	545 lactating mothers consumed 6 × 500 g capsules of either high DHA fish oil (0.90 g DHA + 0.20 g EPA) or soy oil (placebo) for ∼ 5 weeks.	Infants; 0–18 months	4.5: 1*	Overall, a DHA dose of approximately 1% total fatty acids in early life did not increase Maternal Development Index (MDI) scores of preterm infants born earlier than 33 weeks, but did improve the MDI scores of girls.	No effect +	Nu-Mega Ingredients (Clover), Australia
(Clayton et al., 2009) European journal of clinical nutrition	To test the effectiveness of n-3 LC-PUFA supplementation in the treatment of mania and depression in juvenile BD (JBD) when given as an adjunct to standard pharmacological treatment.	An open-label study.	18 boys and girls with juvenile bipolar disorder received supplements (1.56 g DHA + 0.36 g EPA/day) for 6 weeks.	6 (mean)	4.3: 1	RBC EPA and DHA were significantly higher following supplementation. Clinician ratings of mania and depression were significantly lower and global functioning significantly higher after supplementation. Parent ratings of internalizing and externalizing behaviours were also significantly lower following supplementation.	+	Nu-Mega Ingredients (Clover), Australia
(Lee et al., 2013) Psychopharmacology	To investigate the effects of fish oil supplementation on cognitive function in elderly persons with mild cognitive impairment (MCI).	A randomized, double-blind, placebo-controlled trial.	36 low-socioeconomic-status elderly men and women were randomized to placebo corn oil or an isocaloric fish oil (0.43 g DHA + 0.15 g EPA) for 12 months.	>60	2.8: 1	Fish oil has a potential role in improving memory function in MCI subjects.	+	EPAX 1050TG; EPAX AS, Norway
(Mozurkewich et al., 2013) American Journal of Obstetrics and Gynecology	To test the relative effects of EPA- and DHA-rich fish oils on the prevention of depressive symptoms among pregnant women at an increased risk of depression.	A randomized, double-blind, placebo-controlled trial.	126 pregnant women at risk for depression were randomized to soy oil placebo, EPA-rich fish oil (0.27 g DHA + 1.06 g EPA), or DHA-rich fish oil (0.90 g DHA 0.18 g EPA) for ∼26 weeks .	30 (mean)	5.0: 1	Supplementation with fish oil high in EPA or DHA did not prevent depressive symptoms during pregnancy or postpartum.	No effect	ProDHA, Nordic Naturals, USA
(Souied et al., 2013) Ophthalmology	To evaluate the efficacy of docosahexaenoic acid (DHA)–enriched oral supplementation in preventing exudative age-related macular degeneration (AMD).	A randomized, placebo-controlled, double-blind, parallel, comparative study.	263 men and women with early lesions of age-related maculopathy were randomized to olive oil or daily fish oil (0.84 g DHA+ 0.27 g EPA) for 3 years.	55-85	3.1: 1	In patients with unilateral exudative AMD, 3 years of oral DHA-enriched supplementation had the same effect on choroidal neovascularization incidence in the second eye as the placebo.	No effect	Reti-Nat, Bausch & Lomb, France
(Stonehouse et al., 2013) American Journal of Clinical Nutrition	To investigate whether a DHA supplement improves cognitive performance in healthy young adults, and whether sex and APOE modulate the response.	A randomized, double-blind, placebo-controlled trial.	176 healthy men and women were randomly assigned to DHA group (three 750 mg capsules/day, providing 1.16 g DHA + 0.17 g EPA) or placebo group (high-oleic acid sunflower oil) for 6 months.	18-45	6.8: 1	DHA supplementation improved memory and the reaction time of memory in healthy, young adults whose habitual diets were low in DHA. The response was modulated by sex.	+	Efamol, New Zealand
(Phillips et al., 2015) International Journal of Molecular Science	To determine if an increasing intake of DHA and EPA through supplementation is beneficial to cognition and mood in individuals with cognitive impairment no dementia (CIND) or Alzheimer's disease (AD).	A randomized, double-blind, placebo-controlled trial.	57 men and women with CIND, and nineteen with AD, were randomized to olive oil or fish oil (0.62 g DHA + 0.60 g EPA) for 4 months.	71 (mean)	1.0: 1	Even though n-3 fatty acid supplementation elevates plasma concentrations of DHA and EPA in individuals with CIND and AD, this does not benefit cognition and mood in these populations.	No effect	Not specified
(Andrieu et al., 2017) The Lancet Neurology	To test the effect of n-3 polyunsaturated fatty acid supplementations and a multidomain intervention (physical activity, cognitive training, and nutritional advice), alone or in combination, compared with placebo, on cognitive decline.	A randomized, placebo-controlled trial.	1680 men and women with memory complaints were randomly assigned to one of four treatment regimens over 3 years, including multidomain intervention plus n-3 PUFA (0.80 g DHA + 0.22 g EPA), multidomain intervention plus placebo, n-3 PUFA, or placebo alone.	≥70	3.6: 1	The multidomain intervention and polyunsaturated fatty acids, either alone or in combination, had no significant effects on cognitive decline over 3 years in elderly people with memory complaints.	No effect	Pierre Fabre Médicament, France
(Rogers et al., 2008) British Journal of Nutrition	To evaluate the effects of EPA plus DHA supplementation (1·5 g/d) on mood and cognitive function in mild to moderately depressed individuals.	A double-blind, randomized, controlled trial.	218 mildly moderate depressed male and female individuals were instructed to consume either three fish oil (0.85 g DHA + 0.63 g EPA) or olive oil capsules per day for 12 weeks.	18-70	1.3: 1	Substantially increasing EPA plus DHA intake for 3 months was found to have no beneficial or harmful effects on mood in mild to moderate depression.	No effect	Minami Nutrition SA, Belgium
(Lauritzen et al., 2004) Lipids	To evaluate the biochemical and functional effects of fish oil supplements in lactating mothers.	A placebo-controlled, double-blind, randomized trial.	122 Danish mothers with habitual fish intake below the 50^th percentile of the Danish National Birth Cohort were randomized to olive oil (placebo) or 4.5 g/d fish oil (0.79 g DHA + 0.62 g EPA) for 4 months.	Infants; 4 months	1.3: 1	Maternal fish oil supplementation during lactation did not enhance visual acuity of the infants who completed the intervention. However, the results showed that infants with higher RBC levels of n-3 LC-PUFA had a better visual acuity at 4 months of age.	No effect +	BASF Health and Nutrition, Denmark
(Grenyer et al., 2007) Progress in Neuro-Psychopharmacology & Biological Psychiatry	To test whether taking tuna fish oil confers any additional benefit to conventional outpatient treatment for major depression.	A randomized, double-blind, placebo-controlled, four-month trial.	83 men and women with major depression consumed 8 × 1 g capsules per day of placebo (olive oil) or south pacific tuna oil (2.2 g DHA + 0.6 g EPA) for 16 weeks.	18-75	3.6: 1	Despite large reductions in depression, there were no significant differences at any assessment time point between patients receiving fish oil compared with placebo.	No effect	Nu-Mega Ingredients (Clover), Australia
(Rees et al., 2008) Australian and New Zealand Journal of Psychiatry	To test whether n-3 fatty acid treatment is superior to a placebo in the treatment of perinatal depression.	A double-blind, randomized, placebo-controlled trial.	26 females with major depression during the perinatal period received either fish oil (1.64 g DHA+ 0.41 g EPA) or a placebo (Sunola oil) for 6 weeks.	Fish oil: 31 (mean) Placebo: 34 (mean)	3.9: 1	There was no benefit for n-3 fatty acid supplementation over the placebo in treating perinatal depression.	No effect	Nu-Mega Ingredients (Clover), Australia
(Sinn et al., 2012) British Journal of Nutrition	To investigate the benefits of supplementing a diet with n-3 PUFA, DHA and EPA, for depressive symptoms, quality of life and cognition in elderly people with mild cognitive impairment.	A double-blind, randomized, controlled trial.	50 male and female, elderly people with mild cognitive impairment were randomly allocated to EPA-rich fish oil (0.16 g DHA + 1.67 g EPA), DHA-rich fish oil (1.55 g DHA + 0.40 g EPA), or safflower oil (placebo) for 6 months.	>65	3.9: 1	The results indicate that high DHA and high EPA fish oils exert variable effects on cognitive and physical outcomes and may be effective in treating depressive symptoms and health parameters.	+	Not specified
(Silvers et al., 2005) Prostaglandins, Leukotrienes and Essential Fatty acids	To determine the effect of adding fish oil to existing therapies in participants who were being treated for depression in a community setting.	A randomized, double-blind, placebo-controlled trial.	77 male and female participants were randomly assigned to receive 8 g of either fish oil (2.4 g DHA + 0.6 g EPA) or olive oil (placebo) per day, in addition to their existing therapy, for 12 weeks.	18-65	4.0: 1	Despite an increase in circulating n-3 polyunsaturated fatty acids, there was no evidence that fish oil improved mood when compared to the placebo oil.	No effect	Nu-Mega Ingredients (Clover), Australia
(Jackson et al., 2012c) Biological Psychology	To investigate the effects of supplementation with high DHA fish oil (1 g or 2 g) or placebo on cerebral blood flow in healthy adult non-consumers of oily fish.	A double-blind, placebo-controlled study.	65 healthy men and women were randomly assigned to receive high DHA fish oil at a dose of either 1 g/d (0.45 g DHA + 0.09 g EPA) or 2 g/d (0.90 g DHA + 0.18 g EPA), or placebo (olive oil) for 12 weeks.	18-29	5.0: 1	Supplementation with both doses of fish oil, in comparison with placebo, resulted in significantly increased concentrations of oxyhemoglobin and total levels of hemoglobin, indicative of increased cerebral blood flow, during the cognitive tasks.	+	Not specified

*Personal communication; the DHA: EPA ratio was not specified in the published paper, but was provided by authors of the study upon request.

Table 3. A summary of experimental design and results from human studies testing the effects of high DHA fish oil on other medical aspects.

Reference & Journal	Aim of study	Area of study	Type of study	Number of participants / Test formulation	Age range (years)	DHA: EPA	Results / Conclusion	Outcome	Fish oil supplier
(Hill et al., 2007b) British Journal of Nutrition	To test the combined effect of exercise and n-3 PUFA on immune function, particularly in patients with risk factors for CVD.	Immunity	A randomized, placebo-controlled study.	50 volunteers randomly consumed 6 × 1 g capsules of either sunflower oil (placebo) or high DHA fish oil (1.56 g DHA + 0.36 g EPA) per day for 12 weeks.	25-65	4.3: 1	There was no effect of high DHA fish oil on cytokine production by T cells and monocytes. Superoxide anion production from stimulated blood neutrophils was decreased by fish oil but not by exercise, and this change was negatively correlated with the incorporation of DHA into erythrocytes.	No effect	Nu-Mega Ingredients (Clover), Australia
(Marques et al., 2015) Applied Physiology Nutrition and Metabolism	To investigate the effects of DHA-rich fish oil supplementation on the lipid profile, levels of plasma inflammatory mediators, markers of muscle damage, and neutrophil function in wheelchair basketball players before and after acute exercise.	Immunity	Before-after study in the same patient.	8 male wheelchair basketball athletes with paraplegia received 3 g/d fish oil (1.50 g DHA + 0.30 g EPA) for 30 days.	33.8 (mean)	5.0: 1	High DHA fish oil supplementation reduces the markers of muscle damage, inflammatory disturbances, and neutrophil death induced by acute exercise in wheelchair athletes.	+	DHA OMEGA, Naturalis, Brazil
(Munro and Garg, 2013a) Obesity Research & Clinical Practice	To test whether n-3 LC-PUFA, combined with a reduced energy diet, facilitated weight loss and improvements in blood lipids and inflammatory mediators.	Growth / Body mass	A double-blind, randomized, controlled trial with two parallel groups.	35 obese male and female subjects received 6 × 1 g capsules per day of either sunola oil (placebo) or fish oil (1.62 g DHA + 0.42 g EPA/day) for 12 weeks.	18-60	3.9: 1	There was no significant difference within and between the placebo and the fish oil groups for weight reduction, fat mass reduction or changes in inflammatory biomarkers. Blood lipids, apart from TAGs, reduced by 27% in the fish oil group. There were significant correlations between leptin and weight loss, and leptin and EPA and DHA in the fish oil group.	No effect +	Nu-Mega Ingredients (Clover), Australia
(Gunnarsdottir et al., 2008) International journal of obesity	To assess the effects of fish (lean or oily) and fish oil consumption on blood lipid concentration during weight loss.	Weight loss / Body mass	Randomized, controlled 8-week trial.	324 men and women were randomized to 4 treatment regimens for 8 weeks: sunflower oil capsules, cod diet (3 × 150 g/week, including 0.21 g DHA + 0.05 g EPA/day), salmon diet (3 × 150 g/week including 1.37 g DHA + 0.77 g EPA/day), fish oil capsules (0.43 g DHA + 0.63 g EPA/day).	20-40	Cod diet: 3.8: 1 Salmon: 1.8: 1 Fish oil capsules: 0.6: 1	Weight-loss diets, including oily fish with high DHA, resulted in greater TAG reduction than a diet without fish or fish oil. HDL cholesterol tended to decrease less in salmon and fish oil groups.	+	Lipid Nutrition, The Netherlands
(Sabour et al., 2012) Journal of Research in Medical Sciences	To evaluate the possible effect of n-3 PUFAs on proinflammatory cytokine bone change in chronic spinal cord injured patients.	Immunity	A double-blind, placebo- controlled trial.	82 osteoporotic men and women with a spinal cord injury were randomized to two capsules of placebo oil or high DHA fish oil (435 mg of DHA and 65 mg of EPA/day) for 4 months.	38-40 (mean)	6.7: 1	High DHA fish oil supplementation for 4 months had no significant effect on inflammatory markers.	No effect	Minami Nutrition Co. Belgium
(Zhou et al., 2012) American Journal of Clinical Nutrition	To determine whether n-3 LC-PUFA supplementation in pregnancy reduces the incidence of gestational diabetes mellitus (GDM) or preeclampsia.	Gestational diabetes	A double-blind, multicenter, randomized control.	2399 pregnant women at < 20 weeks’ gestation were randomized to vegetable oil without DHA (placebo) or high DHA fish oil (0.80 g DHA + 0.10 g EPA/day) from trial entry to birth.	29 (mean)	8.0: 1	DHA supplementation of 800 mg/day in the second half of pregnancy does not reduce the risk of GDM or preeclampsia.	No effect	Incromega 500 TG; Croda Chemicals, England
(Manley et al., 2011) Pediatrics	To report the effect of DHA supplementation on long-term atopic and respiratory outcomes in preterm infants. (The Infant Fish Oil Supplementation Study (IFOS).	Asthma / Respiratory and allergy	A multicentre, randomized, controlled trial.	657 preterm infants (< 33 weeks’ gestation) consumed expressed breast milk from mothers who took six 500-mg of either high DHA tuna oil capsules (to achieve a breast milk DHA concentration that was 1% of total fatty acids) or placebo soy oil capsules for 18 months.	Pre-term infants	4.5: 1 *	DHA supplementation for infants of <33 weeks’ gestation reduced the incidence of bronchopulmonary dysplasia in boys and in all infants with a birth weight of <1250 g and reduced the incidence of reported hay fever in boys at either 12 or 18 months. However, the hospitalisation rate for lower respiratory tract issues was not reduced compared with the control.	+ No effect	Nu-Mega Ingredients (Clover), Australia
(Santos et al., 2013) Journal of Sports Science and Medicine	To investigate the effects of DHA-rich fish oil supplementation on lymphocyte function before and after a marathon race.	Immunity	A double-blind, randomized, placebo-controlled trial.	21 male athletes were randomized to vegetable oil capsules or 3 g/d fish oil (1.5 g DHA + 0.3 g EPA) for 60 days.	37±2	5.0: 1	High DHA fish oil supplementation has beneficial effects in preventing some of the changes in lymphocyte function induced by marathon participation.	+	Omega DHA, Naturalis, Brazil
(Toupchian et al., 2016) Journal of Clinical Lipidology	To investigate the effects of DHA-enriched fish oil on the marker of monocyte/macrophage activation factor soluble CD163, asymmetric dimethyl arginine (ADMA), and insulin resistance in type 2 diabetic patients.	Immunity	A double-blind, randomized controlled trial.	72 type 2 diabetic men and women were randomized to placebo oil or high DHA fish oil (1.45 g DHA + 0.40 g EPA/day) for 8 weeks.	56 (average)	3.6: 1	Short-time supplementation with DHA-enriched fish oil decreased sCD163 levels without significant differences in ADMA.	+	Pure encapsulations, USA
(Mansoori et al., 2016) Journal of Nutrigenetics and Nutrigenomics	To investigate (1) the impact of high DHA fish oil supplementation on body composition, plasma adiponectin level, and peroxisome proliferator-activated receptor γ (PPARγ) gene expression, and (2) whether the effect of high DHA fish oil supplementation on the variables is modulated by PPARγ Pro12Ala polymorphism.	Body mass	A randomized, double-blind placebo-controlled trial.	72 patients with type 2 diabetes were randomized to 2.4 g/d placebo oil (paraffin oil) or fish oil (1.45 g DHA + 0.4 g EPA) for 8 weeks. Gender was not specified.	55 (mean)	3.6: 1	High DHA fish oil supplementation favorably modulated body composition in patients with T2DM and could be useful to reduce visceral obesity. Weight, body mass index, fat-free mass, adiponectin level, and PPARγ gene expression changes showed no significant difference between treatments.	+ No effect	Pure Encapsulation Co, USA
(Atwell et al., 2013) Journal of Paediatrics and Child Health	To test the effect of supplemental enteral DHA in high dose (1% DHA) versus a standard dose (0.3% DHA) on the longer term respiratory health of prematurely born babies.	Asthma / Respiratory	A multicentre, randomized, controlled trial.	657 mothers received either a high-DHA diet to achieve a breast milk DHA concentration that was 1% of total fatty acids, or a standard-DHA diet (0.3% of total fatty acids) for 18 months.	Pre-term infants	4.5: 1 *	Hospitalisation for lower respiratory tract problems in the first 18 months for preterm infants was not reduced by neonatal supplementation with 1% DHA compared with 0.3% DHA.	No effect	Nu-Mega Ingredients (Clover), Australia
(Damsgaard et al., 2012) Pediatric Research	To investigate whether bone mass, and markers of bone formation and growth, were associated with DHA status and affected by fish oil supplementation in adolescent boys.	Bone	A randomized trial.	78 healthy, slightly overweight boys received breads with high DHA fish oil (0.89 g DHA + 0.19 g EPA/day) or a control for 16 weeks.	13-15	4.7: 1	Fish oil strongly increased DHA status. No associations were found between DHA status and bone mineral content, bone area, bone mineral density or the markers of bone formation and growth at baseline. There was a positive association between changes in DHA status and plasma insulin-like growth factor-1 (IGF-1) during intervention.	No effect	Nu-Mega Ingredients (Clover), Australia
(Helland et al., 2001) Pediatrics	To investigate whether dietary supplementation of n-e PUFAs to pregnant and lactating mothers would affect gestational length, birth weight, and the biochemical status of the neonates.	Gestational length, birth weight	A double-blind, randomized trial.	590 pregnant women were randomized to receive 10 mL of cod liver oil (1.18 g DHA + 0.80 g EPA) or corn oil (placebo) from 18 weeks’ gestation until 3 months after delivery.	Infants; 3, 6, 9, 12 months	1.5: 1	Neither harmful nor beneficial effects of maternal supplementation of n-3 PUFAs was found regarding pregnancy outcome, cognitive development, or growth, as compared with supplementation with n-6 fatty acids.	No effect	Peter Moller, Norway
(Gorjão et al., 2006) Clinical Nutrition	To investigate the effect of high DHA fish oil supplementation on human leukocyte function.	Immunity	Before-after study in the same patient.	10 male subjects received 3 g/d fish oil (1.62 g DHA + 0.78 g EPA) for 2 months.	25-45	2.1: 1	High DHA fish oil increased the phagocytic activity in neutrophils and monocytes, neutrophil chemotactic, and the rate of production of reactive oxygen species by neutrophils.	+	Naturalis Alimentors Naturais Ltda (Sao Paulo, Brazil)
(Vedin et al., 2008) American Journal of Clinical Nutrition	To determine the effects of dietary supplementation with an n-3 fatty acid preparation rich in DHA on release of cytokines and growth factors from peripheral blood mononuclear cells (PBMCs).	Immunity	A randomized, double-blind, placebo-controlled trial.	204 men and women with Alzheimer disease (AD) were randomized to placebo or fish oil (1.7 g DHA + 0.6 g EPA/day) for 6 months.	73 (mean)	2.8: 1	AD patients treated with high DHA supplementation increased their plasma concentrations of DHA (and EPA), which were associated with reduced release of IL-1β, IL-6, and granulocyte colony-stimulating factor from PBMCs.	+	EPAX 1050TG; Pronova Biocare A/S, Lysaker, Norway
(Ramirez-Ramirez et al., 2013) Oxidative Medicine and Cellular Longevity	To evaluate the efficacy of fish oil supplementation on serum proinflammatory cytokine levels, oxidative stress markers, and disease progression in multiple sclerosis (MS).	Immunity	A double-blind, randomized, placebo-controlled trial.	50 men and women with relapsing-remitting MS were randomized to placebo oil or 4 g/d fish oil (1.6 g DHA + 0.8 g EPA) for 12 months.	18-55	2.0: 1	Fish oil supplementation is highly effective in reducing the levels of cytokines and nitric oxide catabolites in patients with relapsing-remitting MS.	+	Omega Rx capsules, USA
(Freund-Levi et al., 2014) Journal of Alzheimer's Disease	To evaluate systemic oxidative stress and inflammatory biomarkers following oral supplementation of dietary n-3 fatty acids.	Immunity	A randomized, double-blind placebo-controlled trial.	40 men and women with moderate Alzheimer's disease (AD) were randomized to placebo oil or an isocaloric oil containing 1.7 g DHA + 0.6 g EPA, for 6 months.	70 (mean)	2.8: 1	Supplementation of n-3 fatty acids in patients with AD for 6 months does not have a clear effect on free radical-mediated formation of F2-isoprostane or cyclooxygenase-mediated formation of prostaglandin F2 alpha.	No effect	EPAX1050 TG, Pronova Biocare A/S, Norway
(Munro and Garg, 2012) British Journal of Nutrition	To test whether n-3 LC-PUFA, combined with a very-low-energy diet, facilitated weight loss, weight maintenance, and improvements in blood lipids and inflammatory mediators.	Growth / Body mass	A double-blind, randomized, parallel- controlled trial.	32 obese male and female subjects received 6 × 1 g capsules per day of high DHA fish oil (1.62 g DHA+ 0.42 g EPA) or sunola oil (placebo) for 14 weeks. Both groups were on a very low energy diet for 4 weeks, which was then followed by 10 weeks of weight maintenance.	18-60	3.9: 1	There was a significant reduction in fat mass for the fish oil group at week 14 but not for the placebo group. However, supplementation with n-3 LC-PUFA had no significant effect on weight loss or weight maintenance over the 14 weeks.	+ No effect	Nu-Mega Ingredients (Clover), Australia
(Munro and Garg, 2013b) Food & Function	To test whether supplementation with n-3 LC-PUFA alone, compared to being consumed concomitantly with a very low energy diet, facilitated weight loss, improvements in blood lipids and positive changes to inflammatory mediators.	Growth / Body mass	A double-blind, randomized, controlled trial, with two parallel groups.	39 obese male and female subjects received 6 × 1 g capsules per day of either sunola oil (placebo) or fish oil (1.62 g DHA + 0.42 g EPA/day) for 14 weeks. Both groups were on a very low energy diet for 4 weeks, which was then followed by 10 weeks of weight maintenance.	18-60	3.9: 1	At 4 weeks, levels of EPA and DHA increased two-fold in the fish oil group, with no significant changes to anthropometric measurements for either group. At 8 weeks, a significant 3-way interaction between time, group and gender was observed for percentage reduction in weight and BMI, with a greater percentage decrease for females in fish oil group compared with placebo for weight and BMI. Supplementation with n-3 LC-PUFA had a time dependent effect on weight loss in females.	+	Nu-Mega Ingredients (Clover), Australia
(Kew et al., 2004) American Journal of Clinical Nutrition	To determine the effects of supplementation with an EPA- or DHA-rich oil on a range of immune outcomes representing key functions of human neutrophils, monocytes, and lymphocytes in healthy humans.	Immunity	A placebo-controlled, double-blind, parallel study.	42 healthy men and women were randomized to olive oil, EPA-rich fish oil (0.73 g DHA + 4.75 g EPA) or DHA-rich fish oil (4.91 g DHA + 0.85 g EPA) for 4 weeks.	23-65	5.8: 1	Supplementation with DHA, but not with EPA, suppresses Tlymphocyte activation, as assessed by expression of CD69. EPA alone does not, therefore, influence CD69 expression. No other marker of immune function assessed in this study was significantly affected by either EPA or DHA.	+ No effect	Not specified
(Tihista and Echavarria, 2017) Clinical Nutrition	To investigate the effect, particularly on infectious Complications, of enteral nutrition enriched with n-3 PUFAs in burn patient	Skin	A prospective, randomized double-blind Trial.	106 male and female burn patients admitted to intensive care randomly received either a standard low-fat diet or a low-fat diet in which 50% of the fat was replaced by fish oil, for 14 days.	40 (approx.)	2.5: 1	The inclusion of n-3 PUFAs in a low-fat diet in ICU burned patients was associated with significant clinical benefits compared with a conventional low-fat diet, with lower rates of severe sepsis, septic shock and pyloric dysfunction.	+	VIPEZ of Landasur Laboratory, Uruguay
(Kew et al., 2003) American Journal of Clinical Nutrition	To determine the effects of enriching the diet with ALA or EPA plus DHA on immune outcomes representing key functions of human neutrophils, monocytes, and lymphocytes.	Immunity	A placebo-controlled, double-blind, parallel study.	150 moderately hyperlipidemic, but otherwise healthy men and women were randomized to control oil, 0.28 g DHA + 0.18 g EPA/day, 0.76 g DHA + 0.49 g EPA/day, 3.7 g ALA/day, or 8.7 g ALA/day for 6 months.	25-72	1.5: 1	An intake of ≤ 9.5 g ALA/day or ≤ 1.7 g EPA and DHA/day does not alter the functional activity of neutrophils, monocytes, or lymphocytes, but it changes the fatty acid composition of mononuclear cells.	No effect	Roche Vitamins Ltd, Basel
(Wallace et al., 2003) British Journal of Nutrition	To determine the effect of enriching the diet with different doses of fish oil or with a modest dose of ALNA on a range of functional responses of human monocytes and lymphocytes.	Immunity	A randomized, placebo-controlled, double-blind, parallel study.	40 healthy males were randomized to control oil, 3.5 g/d ALNA, 0.44 g/d DHA + EPA, 0.94 g/d DHA + EPA, or 1.9 g/d DHA + EPA, for 12 weeks	18-39	1.9: 1 2.5: 1 2.8: 1	Except for IL-6 production, a modest increase in intake of either ALNA or EPA plus DHA does not influence the functional activity of mononuclear cells. The threshold of EPA and DHA intake that results in decreased IL-6 production is between 0·44 and 0·94 g/d.	No effect +	Not specified

*Personal communication; the DHA: EPA ratio was not specified in the published paper, but was provided by authors of the study upon request.

Table 4. A summary table for follow-up studies testing the effects of high DHA fish oil in humans.

Reference & Journal	Aim of study	Area of study	Type of study	Number of participants / Test formulation	Age range (years)	DHA: EPA	Results / Conclusion	Outcome	Fish oil supplier
(Smithers et al., 2010) The American Journal of Clinical Nutrition	To test whether feeding preterm infants milk with a higher DHA content than that used in current practice influences language or behavior in early childhood.	Brain	A follow-up study in a subgroup of infants enrolled in DINO (a double-blind, randomized, controlled trial).	Female participants received either tuna fish oil capsules (0.90 g DHA + 0.20 g EPA) which increased breast-milk DHA concentrations to 1% of total fatty acids, or soy oil capsules (no DHA) which does not alter the DHA content of breast milk; 0.2- 0.3% total fatty acids as DHA.	26 months (corrected age), and between 3 and 5 years (corrected age)	4.6: 1*	Feeding preterm infants milk containing 3 times the standard amount of DHA did not result in any clinically meaningful change to language development or behavior when assessed in early childhood.	No effect	Nu-Mega Ingredients (Clover), Australia
(Lauritzen et al., 2005) Reproduction Nutrition Development	To determine if an increased content of DHA in breast-milk via maternal fish oil supplementation affects mental development in term infants.	Brain	A double-blind, randomized trial, with follow up.	122 Danish mothers were randomized to olive oil (placebo) or 4.5 g/day fish oil (0.79 g DHA + 0.62 g EPA).	Children; 9, 12, 24 months	1.3: 1	Maternal fish oil supplementation during the first four months of lactation was found to have no beneficial effect on problem solving, although the data indicates there may be an effect in girls. Maternal fish oil supplementation was found to result in a reduction in vocabulary comprehension at one year of age, especially in boys.	No effect	BASF Health and Nutrition A/S, Denmark
(Cheatham et al., 2011) Lipids	To examine whether fish oil supplementation during lactation affects processing speed, working memory, inhibitory control, and socioemotional development at 7 years.	Brain	A double-blind, randomized trial, with follow up.	122 Danish mothers were randomized to olive oil (placebo) or 4.5 g/d fish oil (0.79 g DHA + 0.62 g EPA).	7 (mean)	1.3: 1	The authors found that boys whose mothers consumed fish oil had lower prosocial scores relative to the control group. Moreover, speed of processing scores and inhibitory control/working memory scores were differentially negatively predicted by maternal n-3 LCPUFA intake and infant RBC–DHA status.	-	BASF Health and Nutrition A/S, Denmark
(Helland et al., 2003) Pediatrics	To examine the effect of supplementing pregnant and lactating women with n-3 PUFAs on mental development of the children, compared with maternal supplementation with n-6 PUFAs.	Brain	A double-blind, randomized trial, with follow up.	590 pregnant women were randomized to receive 10 mL of cod liver oil (1.18 g DHA + 0.80 g EPA) or placebo corn oil from 18 weeks’ gestation until 3 months after delivery.	4 (mean)	1.5: 1	Maternal intake of n-3 PUFAs during pregnancy and lactation may be favourable for mental development of children at 4 years of age.	+	Peter Moller, Norway
(Helland et al., 2008) Pediatrics	To examine the effect of supplementing pregnant and lactating mothers with n-3 PUFAs on children's IQ.	Brain	A double-blind, randomized trial, with follow up.	590 pregnant women were randomized to receive 10 mL of cod liver oil (1.18 g DHA + 0.80 g EPA) or placebo corn oil from 18 week’ gestation until 3 months after delivery.	7 (mean)	1.5: 1	No significant differences in IQ scores were found between children at 7 years of age whose mothers had taken cod liver oil or corn oil.	No effect	Peter Moller, Norway
(Dunstan et al., 2008) Archives of Disease in Childhood. Fetal and Neonatal Edition	To assess the effects of antenatal n-3 PUFAs on cognitive development in a cohort of children whose mothers received high-dose fish oil in pregnancy.	Brain	A double-blind, randomized trial, with follow up.	98 pregnant women randomly received either fish oil (2.2 g DHA + 1.1 g EPA/day) or olive oil (placebo) from 20 weeks’ gestation until delivery.	2.5 (mean)	2.0: 1	Children in the fish oil-supplemented group attained a significantly higher score for eye and hand coordination than those in the placebo group.	+	Ocean Nutrition Canada, Ltd., Canada
(Meldrum et al., 2015) Nutrients	To investigate the long-term effect (12 years) of fish oil supplementation in pregnancy on neurodevelopment.	Brain	A double-blind, randomized trial, with follow up.	98 pregnant women randomly received either fish oil (2.2 g DHA + 1.1 g EPA/day) or olive oil (placebo) from 20 weeks’ gestation until delivery.	12 (mean)	2.0: 1	There were no significant differences for any of the neurodevelopmental assessment measures completed.	No effect	Ocean Nutrition Canada, Ltd., Canada
(Collins et al., 2011) British Journal of Nutrition	To test the effect of higher-dose DHA (approximately 1% dietary fatty acids) on the growth of pre-term infants up to 18 months corrected age, compared with standard feeding practice.	Growth in pre-term infants	A multi-centre, randomized, controlled trial (DINO trial).	Lactating mothers consumed 6 × 500 g capsules of either high DHA fish oil (0.90 g DHA + 0.20 g EPA) or placebo soy oil per day.	Infants; 0–18 months	4.5: 1 *	There was no effect of higher DHA on weight or head circumference at any age, but infants fed a higher dose of DHA were 0.7 cm longer at 18 months corrected age.	No effect +	Nu-Mega Ingredients (Clover), Australia
(Muhlhausler et al., 2016) American Journal of Clinical Nutrition	To determine whether maternal DHA supplementation during the second half of pregnancy results in a lower BMI and percentage of body fat in children.	Growth	A follow up study (DOMInO trial).	Women with a singleton pregnancy were provided with high DHA fish oil capsules (0.8 g DHA + 0.1 g EPA/day) or placebo vegetable oil capsules in the second half of pregnancy.	3-5	8.0: 1	Maternal intake of high DHA fish oil during the second half of pregnancy does not affect the growth or body composition of children at 3 or 5 years of age.	No effect	Incromega 500 TG, Croda Chemicals, England
(Best et al., 2016) Pediatrics	To determine whether protective effects for allergy were evident in the 6-year-old offspring of women supplemented with n-3 rich fish oil during pregnancy.	Allergy	A follow up of a double-blind, multi-centre, randomized, controlled trial (DOMInO trial).	Women with a singleton pregnancy were provided with high DHA fish oil capsules (0.8 g DHA + 0.1 g EPA/day) or placebo vegetable oil capsules in the second half of pregnancy.	6	8.0: 1	Prenatal n-3 LC-PUFA supplementation did not reduce IgE-associated allergic disease of children at 6 years of age.	No effect	Incromega 500 TG, Croda Chemicals, England

*Personal communication; the DHA: EPA ratio was not specified in the published paper, but was provided by authors of the study upon request.

Table 5. A summary of animal studies testing the effects of high DHA fish oil on heart functioning and exercise performance.

Reference & Journal	Aim of study	Area of study	Number of participants / Test formulation	DHA: EPA	Results / Conclusion	Outcome	Fish oil supplier
(Owen et al., 2004) Lipid	To examine the dose and time responses for incorporation of n-3 PUFA into cellular membranes in rats fed diets containing fish oil.	Heart	Male Sprague-Dawley rats were fed a 10% fish oil diet (32 g DHA + 7.9 g EPA per kg of diet) for periods ranging from 0 to 42 days (n = 3). For the dose response study, rats (n = 3) were fed 0, 1.25%, 2.5%, 5% or 10% fish oil for 4 weeks.	4.0: 1	This study shows that low doses of fish oil produce marked changes in myocardial DHA levels; maximal incorporation takes up to 28 days to occur.	+	Nu-Mega Ingredients (Clover), Australia
(Abdukeyum et al., 2008) The Journal of Nutrition	To evaluate the efficacy of dietary fish oil in providing cardio-protection under the same conditions as ischemic preconditioning (IPC) and to evaluate their potential synergy.	Heart	54 male Wistar rats were fed 10% fat diets containing either 7% tuna oil (20.2 g DHA + 4.9 g EPA/kg diet) + 3% olive oil, 5% sunflower seed oil + 5% olive oil, or 7% beef tallow + 3% olive oil for 6 weeks (n = 6-9).	4.1: 1	Heart function and infarction did not differ among dietary IPC groups. Arrhythmias was significantly reduced by IPC in (n-6) PUFA, and SF hearts were significantly lower in (n-3) PUFA IPC hearts.	+	Nu-Mega Ingredients (Clover), Australia
(Abdukeyum et al., 2016) Clinical Medicine	To test the hypothesis that incorporation of n-3 LC-PUFA into myocardial membranes increases their peroxidation potential and basal fatty acid oxidation.	Heart / Mitochondrial function	54 male Wistar rats were randomly assigned to a diet of either fish oil (7% fish oil + 3% olive oil, providing 20.2 g DHA + 4.9 g EPA/kg diet), sunflower seed oil (5% sunflower seed oil + 5% olive oil) or beef tallow (7% beef tallow + 3% olive oil) for six weeks (n = 6).	4.1: 1 *	High DHA fish oil raised basal membrane DHA, fatty acid peroxidisability index, concentrations of lipid oxidation products, and superoxide dismutase activity (but not glutathione peroxidase).	+ No effect	Nu-Mega Ingredients (Clover), Australia
(Slee et al., 2010) Journal of Lipid Research	To measure the incorporation of DHA into myocardial membranes of rats from low dietary fish oil intake within the human dietary range and quantitatively assess the influence of dietary n-6 PUFA.	Heart	Rats were fed a diet containing one of the following concentrations of fish oil (0.16, 0.31, 0.63, 1.25, 5.0%; n = 4 per diet) or a control diet for 4 weeks. Gender not specified.	4.0: 1	Myocardial membranes are sensitive to absolute dietary intake of n-3 LC- PUFA at low % in the rat, equivalent to a human intake of one meal of fatty fish per week or less. Myocardial DHA concentration increased in a log-linear fashion, with a dietary threshold of 0.019% en as EPA + DHA and half maximal dietary [EPA + DHA] equal to 0.29% en.	+	Nu-Mega Ingredients (Clover), Australia
(Molinar-Toribio et al., 2015) British Journal of Nutrition	To explore the effect of EPA and DHA supplementation in different proportions on spontaneously hypertensive obese rats.	Heart	28 female spontaneously hypertensive, obese rats were randomly divided into four groups, each supplemented with a different oil mixture (control oil or DHA: EPA oil mix at a ratio of 1: 1, 1: 2, 2: 1) for 13 weeks (n = 7).	2.0: 1	Specific mixtures significantly decreased inflammation (CRP levels, DHA: EPA ratio of 1: 1 and 1: 2), increased the activity of antioxidant enzymes (SOD in erythrocytes and abdominal fat, DHA: EPA ratio of 1: 1; SOD, CAT, GR, GPx in kidneys, DHA: EPA ratio of 2: 1). No significant differences were found for HDL-cholesterol in all groups.	+ No effect	AFAMPES 121 EPA (AFAMSA), Spain EnerZona Omega 3 RX and Oligen liquid DHA 80% (IFIGEN-Equip 98, S.L.), Spain
(Higuchi et al., 2006) Annals of Nutrition and Metabolism	To examine the weekly changes in plasma glucose and lipid concentrations in mice fed experimental diets that contained fish oil, DHA, and/or EPA to discuss the effects of DHA and/or EPA intake on glucose and lipid metabolism.	Heart (glucose and lipid metabolism)	45 male mice were fed five different experimental diets (n = 9) which contained 6.0% lard, 6.0% fish oil (14.28 g DHA + 4.02 g EPA/kg diet), 1.5% DHA + 4.5% lard, 0.4% EPA + 5.6% lard or 1.5% DHA + 0.4% EPA + 4.1% lard, for 17 weeks.	3.5: 1	The decreases in plasma glucose concentrations in response to intakes of DHA and EPA in mice take place over a longer period of time than similar decreases in the plasma lipid concentrations.	+	Nippon Chemical Feed Co. Ltd, Hakodate, Japan
(Huggins et al., 2009) American Journal of Physiology – Heart and Circulatory Physiology	To investigate whether dietary n-3 PUFA could provide ischemic protection in female mice with an underlying genetic predisposition to cardiac hypertrophy.	Heart	Mature female transgenic mice and littermate wild-type mice were fed a fish oil-derived diet (20.20 g DHA + 4.87 g EPA/kg diet) or control diet, for 4 weeks (n = 8).	4.1: 1*	Dietary fish oil did not suppress the incidence of reperfusion arrhythmias in mice.	No effect	Nu-Mega Ingredients (Clover), Australia
(Arai et al., 2009) Journal of Atherosclerosis and Thrombosis	To elucidate the effects of EPA- or DHA-rich fish oil, and of the latter plus fenofibrate, on lipid metabolism in female mice.	Heart (lipid metabolism)	20 female KK mice were divided into four groups and fed one of three diets for 8 weeks; lard/safflower oil (4:6), EPA-rich fish oil (13.6 g DHA + 21.0 g EPA/kg diet), high DHA fish oil (25.2 g DHA + 7.3 g EPA/kg diet), or high DHA fish oil plus 0.2% fenofibrate (n = 5).	3.4: 1	Fish oil inhibited body weight gain and exhibited an anti-obesity effect through the inhibition of lipid synthesis in female KK mice.	+	NOF Corporation (Tokyo, Japan)
(Castellano et al., 2010) British Journal of Nutrition	To examine the effects of a long-term dietary supplement of fish oil in adult male pigs on body condition as well as insulin sensitivity and secretion.	Heart (insulin metabolism)	15 Duroc boars received a daily 2.5 kg basal diet with a supplement of either 62 g animal fat (rich in SFA), 60 g menhaden oil (10.8 g DHA + 9.0 g EPA), or 60 g tuna oil (19.8 g DHA + 3.9 g EPA) for 7 months.	1.2: 1 5.1: 1	Long-term supplementation with dietary n-3 PUFA did not affect insulin metabolism in healthy adult male pigs.	No effect	Bluecina Corp (Calgary, AB, Canada)
(Ninio et al., 2005) Journal of Cardiovascular Electrophysiology	To examine the effect of dietary fish oil on the rabbit model of stretch-induced vulnerability to atrial fibrillation.	Heart	Six-week-old rabbits were fed standard rabbit pellets supplemented with 5% tuna fish oil (13 g DHA + 3 g EPA/kg diet, n = 6) or supplemented with 5% sunflower oil (n = 6) for 12 weeks. Gender not specified.	4.3: 1	Red blood cell, atrial, and ventricular n-3 fatty acid levels were significantly higher in the fish oil group and this is associated with protection against stretch-related AF in the rabbit.	+	Nu-Mega Ingredients (Clover), Australia

*Personal communication; the DHA: EPA ratio was not specified in the published paper, but was provided by authors of the study upon request.

Table 6. A summary of animal studies testing the effects of high DHA fish oil on the brain and visual system.

Reference & Journal	Aim of study	Area of study	Number of participants / Test formulation	DHA: EPA	Results / Conclusion	Outcome	Fish oil supplier
(Fernandes et al., 2008) Nutrition Research	To investigate whether long-term treatment with commercial, high DHA fish oil could be effective in alleviating both the cognitive and neurodegenerative deficits caused by transient, global cerebral ischemia in rats.	Brain	40 young adult male Wistar rats received cognition training for 10 days. They were then divided into 3 groups: sham operation, ischemia + vehicle, or ischemia + fish oil (0.3 g DHA + 0.06 g EPA/kg body weight).	5.0: 1	Long-term fish oil treatment is able to facilitate functional recovery after ischemic brain damage, an effect that was distinct from hippocampal damage but did not prevent hippocampal damage in rats.	+ No effect	n-3 DHA 250, Biotik do Brasil Industria e Comercio Ltda, Brazil
(Engstrm et al., 2009) Upsala Journal of Medical Science	To investigate the effects of two different types of natural fish oils containing different amounts of the n-3 PUFAs EPA and DHA and antioxidants on plasma and brain fatty acids, blood lipids, vitamin E, and in vivo lipid peroxidation, as well as brain nitric oxide synthase (NOS) activity.	Brain	24 male, pathogen-free Sprague-Dawley rats were divided into four groups and received either butter (control), EPA-rich fish oil plus antioxidant (5.85 g DHA + 8.7 g EPA/kg diet), high DHA fish oil plus antioxidant (14 g DHA + 3.85 g EPA/kg diet), or high DHA fish oil (14 g DHA + 3.85 g EPA/kg diet) not fortified with antioxidant, for 10 days.	3.6: 1	Both the EPA- and DHA-rich diets affected the blood lipids in a similarly positive manner, and they both had a large impact on plasma phospholipid fatty acids. The intake of DHA was more important than that of EPA for brain phospholipid DHA enrichment and brain NOS activity.	+	EPA-rich oil (ESKIMO-3, Cardinova, Sweden High DHA oil (EPAX 0525TG, Pronova, Norway
(Trofimiuk and Braszko, 2011) Lipids	To test the hypothesis that the active constituents of cod liver oil alleviate the negative impact of prolonged restraint stress on cognitive functions of male Wistar rats.	Brain	75 male Wistar rats were divided into four treatment regimens including Cremophor, Cremophor followed by stress procedure, cod liver oil (0.30 g DHA + 0.22 g EPA/kg body weight) and cod liver oil followed by stress procedure.	1.3: 1	Cod liver oil administration significantly prevented the deleterious effects of chronic restraint stress on recall and the spatial memory.	+	Cod Liver Oil, Lysi HF, Island
(Avramovic et al., 2012) Hippokratia	To investigate the effects of dietary n-3 fatty acid supplementation on levels of lipid peroxidation and oxidant/antioxidant status of brain tissue in rats.	Brain	16 male Wistar rats were divided into two groups. One received standard laboratory food and the other received standard laboratory food and 200 µl fish oil (0.04 g DHA + 0.03 g EPA/day).	1.5: 1	Incorporation of n-3 fatty acids after their supplementation had beneficial effects on brain tissue. Catalase activity decreased but not significant.	+ No effect	Not specified
(Clouard et al., 2015) Journal of Nutrition	To assess the impact of maternal dietary DHA on behavior, brain fatty acid profile, and sickness response of offspring in pigs.	Brain	24 pregnant sows were fed a diet with high DHA fish oil (2.02 g DHA + 0.27 g EPA/kg body weight) or high-oleic acid sunflower oil from day 61 of gestation through to lactation.	7.0: 1	Maternal DHA beneficially affected social behaviour in offspring after weaning, and mildly attenuated sickness behaviour after an inflammatory challenge in pigs.	+	Marinol D-40; Stepan Lipid Nutrition, USA
(Davis et al., 2017) Brain, Behavior, and Immunity	To determine the contribution of DHA on anxiety and depressive-like behaviours through modulation of the gut microbiota in a paradigm of social isolation.	Brain	36 male and female C57BL/6J mice were randomly placed on one of three dietary conditions including a control diet with no performed DHA, a control diet supplemented with 0.1% by weight DHA, or a control diet supplemented with 1.0% by weight DHA.	9.2: 1	DHA altered commensal community composition and produced beneficial effects on anxiety and depressive-like behaviors in a sex-specific manner.	+	Omega Protein Inc., USA

Table 7. A summary of animal studies testing the effects of high DHA fish oil for other medical purposes.

Reference & Journal	Aim of study	Area of study	Number of participants / Test formulation	DHA: EPA	Results / Conclusion	Outcome	Fish oil supplier
(Peoples and McLennan, 2010) British Journal of Nutrition	To investigate the influence of membrane composition on skeletal muscle function.	Muscle / sport	18 male Wistar rats were fed either saturated fat (SF), n-6 PUFA (linoleic acid rich) or n-3 PUFA (fish oil; 20.20 g DHA + 4.87 g EPA/kg diet) diets for 8 weeks.	4.1: 1	Hindlimb oxygen consumption during contraction was significantly lower in the n-3 PUFA group compared with the SF group, producing a significantly higher O2 efficiency index.	+	Nu-Mega Ingredients (Clover), Australia
(Peoples and McLennan, 2014) British Journal of Nutrition	To test the effects of a fish-oil diet on skeletal muscle fatigue under the stress of contraction using the rat in vivo autologous perfused hindlimb model.	Muscle function	18 male Wistar rats were fed a diet rich in saturated fat (SF), a diet rich in n-6 PUFA or a diet rich in n-3 LC-PUFA DHA (20.20 g DHA + 4.87 g EPA/kg diet) derived from fish oil for 8 weeks.	4.1: 1	Rats fed the n-3 PUFA diet developed higher maximum twitch tension than those fed the SF and n-6 PUFA diets. The n-3 PUFA group used less oxygen for tension developed and produced higher venous lactate concentrations, with no difference in glycogen utilisation compared with the saturated fat and n-6 PUFA groups.	+ No effect	Nu-Mega Ingredients (Clover), Australia
(Henry et al., 2015) British Journal of Nutrition	To test the hypothesis that nutritionally relevant fish oil doses can modulate membrane fatty acid composition and muscle fatigue.	Sport	18 male Sprague–Dawley rats were fed 10% fat diets of either a control fat, or a low (0.9 g DHA + 0.2 g EPA/kg diet) or moderate (3.6 g DHA + 0.9 g EPA/kg diet) fish oil for 15 weeks.	4.1: 1	There were no dietary differences in maximum developed muscle force. Force within bursts was better sustained with fish oil, where maximum rates of force development and relaxation declined more slowly. Incorporation of DHA was greater in the fast-twitch gastrocnemius than in the slow-twitch soleus muscle.	+	Nu-Mega Ingredients (Clover), Australia
(Kohno et al., 2000) Oncology Reports	To investigate the modify effect of dietary tuna oil on the development of azoxymethane (AOM) -induced colonic aberrant crypt foci (ACF).	Colonic diseases	20 male rats were randomized into four groups receiving 5% corn oil, 23.5% corn oil, 5% fish oil, or 23.5% fish oil.	3.4: 1	Fish oil derived from tuna, which contains high amounts of DHA and VD3, suppresses the formation and growth of ACF and may have a preventive effect on colon carcinogenesis.	+	Maruha Co., Ltd., Japan
(Du et al., 2004) Journal of Nutritional Biochemistry	To examine the effects of dietary fatty acids on hepatitis, hepatic gene expression and survival.	Liver	144 rats were fed a conventional, low-fat diet (CE2), a CE2 diet supplemented with lard, soybean oil, or a mixture of high DHA fish oil (3.2 g DHA + 1.4 g EPA/kg diet) and soybean oil.	2.3: 1	Polyunsaturated fatty acids suppress the development of acute hepatitis and prolong survival in females, regardless of whether they are of the n-6 or n-3 type, which are associated with altered gene expressions.	+	Japan Oil Chemicals Inc., Tokyo
(Philp et al., 2015) PLOS ONE	To compare effects of different diets on the metabolic profile and lipid metabolism gene and protein content in red (soleus) and white (extensor digitorum longus) muscles of mice.	Muscle function	Male and female C57BL/6 mice were randomly assigned to one of three diets (n = 9–12/group), fed either a standard chow, high saturated fat (HF-S) or HF-S fish oil diet (19.5 g DHA + 4.5 g EPA/kg diet).	4.3: 1	It is likely that HF-fish oil prevents HF-S-induced intramyocellular lipid accumulation by a concurrent increase in mediators of fatty acid uptake and utilisation, and suppression of mediators promoting fatty acid storage and lipogenesis.	+	Nu-Mega Ingredients (Clover), Australia
(Kook et al., 2002) Asian Australasian Journal of Animal Sciences	To investigate the effect of fish oil on growth performance, ruminal metabolism and fatty acid composition, and physical characteristics of longissimus muscle.	Growth/ heart (serum cholesterol)	10 steers and 10 bulls of Korean cattle were divided into two groups receiving corn grain or 5% fish oil (11.9 g DHA + 1.67 g EPA/kg diet).	7.1: 1	Average daily weight gain and feed efficiency were not influenced by high DHA fish oil. There was a treatment effect for serum cholesterol concentrations. High DHA fish oil increased concentrations of n-3 fatty acids, including linolenic, EPA and DHA in longissimus muscle.	No effect +	Enerlac®, Chile
(Castellano et al., 2011) Theriogenology	To determine the effect of long-term dietary supplementation of two types of fish oil on lipid composition and steroidogenesis in adult pig testis.	Sex hormone production	24 boars were randomized into three dietary groups and fed animal fat rich in SFA, menhaden oil (10.80 g DHA + 9.6 g EPA/day), or tuna oil (19.80 g DHA + 4.20 g EPA/day), for 7 months.	MO: 1.2: 1 TO: 5.0: 1	Long-term dietary supplementation of fish oil, regardless of the EPA/DHA ratio, modified the fatty acid compositions in testis and affected steroid production of healthy adult boars.	+	Virginia prime gold Menhaden fish oil: Omega Protein Inc., USA Tuna oil: Bluecina Inc., Canada
(LeBlanc et al., 2008) American Journal of Veterinary Research	To evaluate the effect of diets enriched with EPA and DHA on in vivo production of inflammatory mediators.	Immunity	15 healthy, crossbred-hound dogs were randomly allocated to receive an isocaloric ration supplemented with either sunflower oil, fish oil, or fish oil plus Vitamin E for 12 weeks.	1.3: 1	A fish oil-enriched diet consisting of EPA and DHA was associated with significant reduction in serum PGE2 concentrations and IL-1 and IL-6 activities.	+	Omega Protein, USA
(Patten et al., 2002) Nutrition Research	To investigate, in relation to newborn guinea pig growth, caecal digesta pH and SCFA profile, ileal total phospholipid fatty acid content and particularly for in vitro ileal contractility.	Gut	Newly formulated commercial rice porridge was fed to 7 new born guinea pigs and their mothers for 2 months, which consisted of essential nutrients and 3% total fat as safflower oil or 3% tuna fish oil.	4.2: 1	The fish oil supplemented group had a significantly higher caecal digesta pH with a significantly lower propionate concentration. The supplementation of fish oil decreased the threshold for electrically induced contraction while decreasing the sensitivity to 8-iso-PGE2.	+ No effect	Nu-Mega Ingredients (Clover), Australia

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