Fatty Acid Profile and Selected Chemical Contaminants in Yellowfin Tuna From the Arabian Sea

Abstract

Fresh yellowfin tuna (n = 110) collected for a period of one year was analyzed for chemical composition, fatty acids, nutrients, and toxic metals. The mean values of investigated minerals were 892, 2834, 0.81, 6.61, 0.38, 11.0, 0.94, 0.59, 0.71, 0.53, and 0.29 mg kg^–1 for Na, K, Cu, Zn, Mn, Fe, Ni, Co, Cr, Sr, and V, respectively. Average Cd, Pb and Hg levels were 0.016, 0.029 and 0.137 mg kg⁻¹, respectively. The average concentrations of saturated, monounsaturated, and polyunsaturated fatty acids were 196.56, 84.8, and 218 mg 100g^–1, respectively. Yellowfin tuna contained higher DHA (148.2 mg 100g^–1) than EPA (29.3 mg 100 g^–1). A meal with 100 g of this species provides 48.6 and 71.05% of the required daily level of protein and EPA+DHA, respectively. Yellowfin tuna showed low thrombogenic (0.27) and atherogenic (0.43) potential and the value obtained for h/H index (1.97) indicates that regular intake of yellowfin tuna may bring hypocholesterolemic effect. All contaminants in the studied fish were either undetectable or present at very low levels when compared to the United States Food and Drug Administration (USFDA), Food and Agriculture Organization/World Health Organization (FAO/WHO), and European Union regulatory standards and yellowfin tuna would be one of the best options for people who frequently consume tuna fish to get sufficient EPA+DHA and essential elements.

Keywords:

• Yellowfin tuna
• Minerals
• EPA
• DHA
• Omega-3 fatty acids

Introduction

A recommendable diet should be able of providing sufficient nutrients containing low levels of contaminants. Fish is one of the most important food items. The nutritional benefits of fish are mainly due to the content of high quality proteins, balanced amino acid composition, vitamins, essential nutrients and also a high amount of omega-3 polyunsaturated fatty acids.^[1,^2] Omega-3 fatty acids have been associated with all kinds of health benefits from warding off depression and cognitive decline to reducing inflammation and the risk of heart disease.^[3] Several international organizations and health agencies have instigated to recommend consumption of the long chain omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid, respectively, in pill or fish form for overall cardiovascular health. The evidence is so good that the American Heart Association has recommended the consumption of fish rich in omega-3 fatty acids at least twice a week in order to reach the daily intake of omega-3 fatty acids recommended for healthy adults with no history of heart disease.^[4] In addition, fish also contains essential minerals and some mineral elements have plenty of benefits to the biological functioning of a human body.^[1]

However, one potential risk of dietary fish eating is its content of chemical contaminants in some fish, which affect the health of people consuming large quantities. Heavy metals are introduced into the environment via natural and anthropogenic processes.^[5,^6] Cadmium is deemed to produce health effects on the respiratory system, induce the renal and hepatic toxicity and has been associated with bone disease, poor reproductive capacity, hypertensions, tumors, and hepatic dysfunction. Lead affects mainly the central nervous system, kidney, and blood. High mercury content in fish may counteract the cardio protective effect of fish intake.^[7] Excessive mercury consumption is implicated in neurodevelopmental defects including mental retardation, cerebral palsy, deafness, blindness and dysarthria, alteration of sensory functions, motor coordination, memory, attention and learning ability, and adult neuro and cardiovascular toxicity.^[7]

Among seafood species, tuna represents one of the most important groups captured in the world. They are known as fatty fish due to their high content of fat mostly polyunsaturated fatty acids and also an excellent source of some essential elements,^[1] however, given the morphological and biological characteristics associated with their habitat, they may accumulate substantial concentrations of chemical contaminants in their tissues and thus, can represent a major dietary source of these contaminants in humans. Although, few studies on the elemental composition of tuna species exists^[8–11] their objectives were mostly related to environmental contamination and its use in biological monitoring. The delicious and nutritious, yellowfin tuna (Thunnus albacares) is one of the world’s most popular pelagic fish and an important component of the tuna fishery in most areas of the world, apart from the Mediterranean Sea. Yellowfin tuna is versatile food fish and the meat is consumed raw, cooked, smoked, and canned. The lean meat is widely used in sashimi, raw fish dishes popular in Japan and a connoisseur’s delicacy in the United States as well. The fish is frequently and widely eaten in many parts of the world, so their toxic metal contents should be of some concern to human health. The primary aim of this work was to quantify the levels of omega-3 fatty acids, a number of essential and toxic elements in yellowfin tuna much enjoyed by the worldwide consumers. From a public health perspective, this study can provide consumers with better knowledge of nutritional characteristics and contamination problems associated with this fish.

Materials and methods

Reagents and Samples

All reagents were analytical reagent grade and milliQ 18 mΩ pure water (MilliQ, Millipore, USA) was used for preparation of reagents and standards. Nitric acid, hydrogen peroxide, sodium hydroxide, hexane, methanol, acetonitrile, boron trifluride in methanol (20%, w/v), and chloroform were purchased from Merck (Darmsadt, Germany). Butylatedhydroxytoluene (BHT) and boron trichloride in methanol (14%) were purchased from Sigma-Aldrich Co., USA. Fatty acid methyl esters (FAME) standards were purchased from Supelco (Belle fonte, PA, USA), the non-adecanoic acid methyl ester (C19:0) internal standard was from Fluka (Buchs, Switzerland). Calibration curves for each of the individual elements were prepared from ICP multi element stocks (Charleston, SC 29420).

Sampling

Yellowfin tuna (Thunnus albacares) samples (n = 110) were caught off by commercial fishing boats along the coast of the Arabian Sea, Oman. The average length and weight were 95.7 ± 21.4 cm ranging from 65–146 cm and 13.7 ± 10.1 kg ranging from 3.33 kg to 42.0 kg, respectively. These results indicated that the specimens were all adults and within commercial size. Fish were preserved on ice in styrofoam boxes and transported to the laboratory. Muscle tissues below the dorsal fin were taken and homogenized. The homogenized material was preserved in freezer bag at –80°C up to 24–48 h.

Analyses

Proximate analyses

Moisture, ash, fat, and protein were determined following the AOAC^[12] methodologies (Sec 950.46, 938.08, 960.39, and 955.04, respectively). Briefly, the moisture content was obtained by drying the sample overnight at 105°C, ash was quantified after combustion for 16 h at 550°C and crude protein content was determined by the Kjeldahl method using a conversion factor of 6.25. Crude fat was determined by a rapid method of total lipid extraction and purification.^[13] The energy value, expressed as kcal 100 g^–1edible part, was calculated using the factors 9.02 4.27 kcal g^–1 for fat and 4.27 kcal g^–1 for protein.

Elements

An accurate sample weight (0.5 ± 0.05 g) of fish tissue was gently digested for 45 min in 8 mL of acid mixture HNO₃/H₂O₂ (7:1 v/v) in Teflon vessel. The sample was then mineralized in Ethos D (Type Ethos plus 1) microwave lab station (Milestone ETHOS PLUS, Italy). The power system used with the focused microwave apparatus provides continuous microwave emission at each power level. The system is a closed vessel microwave apparatus, but it is equipped with a fume extraction system. After mineralization, the samples and the blank solution were brought to 25 mL in volume with milliQ water. All the glassware was treated with a dilute solution of HNO₃ (0.1%) to prevent contamination. The determination and quantification of mineral elements were done by Inductively Coupled Plasma Atomic Emission Spectrometer (ICP AES, ICPE-9000, Shimadzu, Japan). For K, Na, Cu, Zn, Mn, Fe, Ni, Co, Cr, Sr, and V, the detection limit expressed in mg kg^–1 are 0.09, 0.09, 0.02, 0.08, 0.04, 0.09, 0.05, 0.08, 0.8, 0.05, and 0.04, respectively. The detection limits are 0.01 mg kg^–1 for Cd and 0.02 mg kg^–1 for Pb. One gram of each sample was analyzed in triplicate for total mercury using a thermal Decomposition Amalgamation Atomic Absorption Spectrophotometer (DMA-80, Milestone Inc., Italy). The detection limit is 0.5 ng g^–1. Accuracy of the analytical method was monitored by analyzing certified reference materials (IAEA 436—tuna fish flesh homogenate and 407—fish tissue homogenate) and the measured values were well agreed with the certified values. A recovery test was carried out by spiking of standard solutions of heavy metals in homogenized samples. The recovery for heavy metals during these experiments ranged between 80–110% and no batches were outside of these limits.

Fatty acid analysis

Determination of fatty acid profile methyl esters was carried out as described in Araujoa et al.^[14] Saturated fatty acids, mono unsaturated fatty acids and polyunsaturated fatty acids, including linoleic acid (LA, 18:2n-6), -linolenic acid (ALA, 18:3n-3), stearidonic acid (SDA, 18:4n-3), arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA; all-cis-5, 8, 11, 14, 17-eicosapentanoic acid, 20:5n-3), docosapentaenoic acid (DPA, 22:5n-3), and docosahexaenoic acid (DHA; all-cis-4, 7, 10, 13, 16, 19-docosahexaenoic acid, 22:6n-3) were quantified by an Agilent 6890N gas chromatograph (Avondale, PA, USA) equipped with a liquid auto sampler and a flame ionization detector. Data collection was performed by the Agilent GC ChemStation software. Operating conditions were as follows: injection port temperature, 250°C; detector temperature, 255°C; injection volume, 1 µl; split ratio, 10:1; oven programmed from 185°C for 5 min to final hold temperature of 240°C for 15 min with an increase of 4°C/min; helium carrier gas (99.999% pure). The FAME samples were analyzed on a Supelco SP-2560 capillary column (100 m × 0.25 mm I.D. 0.2 µm film thickness, Supelco, Bellefonte, PA, USA). Total analysis time was 60 min. This time interval was sufficient to detect FAME with chains from 4 to 24 carbons in length. The FAME peaks were identified by comparison of their retention times with the retention times of FAME standards. The detection limits varied between 4 and 10 µg/mL. Accuracy of the analytical method was checked by analysis of certified reference material (beef-pork fat blend CRM:163) and the measured values were in the value range of the certified reference material. The hypocholesterolemic/hypercholesterolemic potential of the samples was evaluated according to Santos-Silva et al.^[15] using the following formula:

The atherogenic index (AI) and the thrombogenic index (TI)^[16] (as cited in Senso et al.^[17]) of the fish yellowfin tuna were calculated, with the following formulas:

For AI and TI calculations, the fatty acid concentrations were expressed as g 100 g^–1 of total fatty acids.

Statistical Analysis

All data were analyzed using the using the SPSS software (SPSS, 19, USA). Other calculations were performed by Microsoft Excel 2010 (Microsoft Corp., Redmond, USA).

Results and discussion

Proximate Composition

The moisture, protein, fat, and ash content of the yellowfin tuna samples studied ranged from 69.56 to 72.96, 20.18 to 26.41.7, 2.24 to 4.59, and 1.35 to 2.26 g 100 g^–1, respectively. Based on the fat content, the fish can be considered lean (below 5%) according to the proposed classification by Huss.^[18] The moisture content ranged from 69.5 to 72.9 g 100 g^–1, these values are common in lean species.^[18,^19] The protein value, 24.82 is slightly higher compared to the values reported for typical of lean fish.^[2,¹⁸,^19] Considering the protein recommended dietary allowances of 0.85 g kg^–1 per day for adults and an adult of 60 kg, a meal of 100 g of yellowfin tuna can contribute at least 48.6% of the required daily level of protein. The ash content showed the richness of the yellowfin tuna fish in minerals. Attending the results it can be observed that the mean energy value ranged between 106 and 302 kcal 100 g^–1.

Macro and Trace Elements

Table 1 shows the mean values of the tested macro and trace elements in muscle tissue of yellowfin tuna. Macro elements: The most abundant macro elements were the electrolytes K and Na as shown in Table 1. Of all the elements, K was the most abundant, ranging between 2412–3790 mg kg^–1 with a mean value of 2834 ± 495 mg kg^–1. The range and mean value found in this study agrees with those obtained by several authors for various fish.^[19–21] Regarding sodium, the concentration ranged from 745.6 to 998 mg kg^–1 with a mean value of 892 ± 211 mg kg^–1, which is in agreement with the results obtained by Afonsa et al.^[19] and Oksuz et al.^[20] However, higher concentrations were reported for different fish.^[22,^23] Usually, fish present lower contents of Na when compared to K, either in fish from salt or fresh water.^[19,^22] This fact was also noticed in the studied species. Similar to the present study, these elements were found to be the most abundant minerals in Brazilian and Mexican tuna fish.^[21,^24]

TABLE 1 Elemental contents (wet weight basis) in the muscle of yellowfin tuna

Elements	Mean ± SD (mg kg^–1)	Range (mg kg^–1)	Daily intake (mg)^a
Co	0.59 ± 0.43	0.315-2
Cr	0.71 ± 0.26	0.329-1.38
Cu	0.81 ± 0.31	0.305-1.39	1-1.5
Fe	11.0 ± 4.77	7.88-30.2	15
K	2834 ± 495	2412-3790	2000-5900
Mn	0.38 ± 0.26	0.188-1.57	2-5
Na	892 ± 211	745.6-998	<2300
Ni	0.94 ± 0.50	0.223-2.21	0.025-0.03
Sr^b	0.53 ± 0.15	0.3-0.864	1-5
V	0.29 ± 0.17	0.113-0.66
Zn	6.61 ± 3.01	2.53-39.8	10-15
Hg	0.13 ± 0.09	0.036-0.447
Cd	0.016 ± 0.03	0.008-0.116
Pb	0.029 ±0.08	0.011-0.298

^aBelitz et al. (2004).^[2]

^bAcu-Cell (2007).

Trace elements

Regarding trace elements, the copper concentration in muscle tissue varied from 0.305 to 1.39 mg kg^–1 and the average value of 0.81 ± 0.31mg kg^–1. Copper levels in fish samples have been reported in the range of 0.01–5.33 from the USA,^[10] 0.51–7.05 mg kg^–1 from Turkey^[25] and 0.069-0.384 mg kg^–1 from Serbia.^[26] The FAO/WHO has set a limit for heavy metal intake based on body weight. For an average adult, the provisional tolerable daily intake for copper is 3 mg. The level of Cu did not exceed the permissible limits prescribed by various agencies. Nevertheless, the tolerable upper limit set by the USFDA for Cu (10 mg/day) is well above the results found in this present study (0.305–1.57 mg kg^–1). Copper is essential for good health, but very high intake can cause adverse health problems such as liver and kidney damage.^[27] The upper limit of copper for children and adults is 1 and 10 mg/day, respectively.^[28]

Zinc content in the samples varied from 2.53–39.8 mg kg^–1and the average concentration of zinc in yellowfin tuna was 6.61 ± 3.01 mg kg^–1. Zinc contents in different seafood have been reported in the range of 9.61–19.5 mg kg^–1 from Sweden,^[29] 0.06–39.3 mg kg^–1 from Brazil^[30] and 0.14–97.8 mg kg^–1 from the USA.^[10] The permissible zinc concentration for fish is 50 mg kg^–1[31] and zinc concentration in the samples was well below the maximum permitted concentration of Zn. For an average adult, the provisional tolerable daily intake for zinc is 60 mg.^[32] The recommended daily allowance is 10 mg/day in growing children and 15 mg/day for adults. Too little zinc can create problems, but too much zinc is also harmful to human health.^[27] The upper limit of zinc for children and adults is 0.2 and 1 mg/day, respectively.^[28]

The manganese concentration in the muscles of yellowfin tuna ranged between 0.18 and 1.57 with the mean of 0.38 ± 0.26 mg kg^–1. The manganese in the literature have been reported in the range of 0.07-7.3 mg kg⁻¹ from Brazil,^[30] 0.49–1.23 mg kg^–1 from Sweden^[29] and 0.01–2.55 mg kg^–1 from the USA.^[10] Manganese deficiency may lead to skeletal disorders, alterations in the growth process and reproductive functions, skin appendages, and to a reduction in cholesterol levels. However, manganese deficiency has not been reported in humans. The upper limit of manganese for children and adults is 2 and 11 mg/day, respectively.^[28,^29]

Iron was found most abundant trace metal in muscle tissue of yellowfin tuna among all the studied trace metals. The concentration of Fe in fish muscle from this study varies between 7.88–30.21 mg kg^–1 (mean, 11.0 ± 4.77 mg kg^–1). Iron contents in the literature have been reported in the range of 13.72–32.6 mg kg^–1 for fish from Turkey^[33] and 0.4–26.1 mg kg^–1 from Brazil.^[30] Our iron concentrations were generally in agreement with the literature. The upper limit of iron in children and adults is 40 and 45 mg/day, respectively.^[28] The RDA of iron for infants and adults is 11 and 8 mg/day, respectively. Fish is a major source of iron for adults and children. The elements such as Cu, Zn, Mn, and Fe play the role of functional elements in various metalloenzymes, which have a particular catalytic function in living organisms. The concentrations of Cu, Zn, Mn, and Fe found in this study suggest that yellowfin tuna may make a significant contribution to the daily intake needs, if consumed regularly.

Nickel concentrations ranged between 0.223 to 2.21 mg kg^–1 with a mean value of 0.94 ± 0.50 mg kg^–1. Reported nickel levels in the literature are in the range of 0.03–0.69 mg kg^–1 for muscles of fish from Indian markets^[8] and 0.0 to 0.78 mg kg^–1 from the USA.^[10] The MRL for nickel is 70–80 mg kg^–1,[34] and the samples analyzed in this present study showed concentrations only up to 2.21 mg kg^–1. Nickel can cause respiratory problems and it is carcinogenic at a higher level.^[27] The upper tolerable intake level of nickel for children and adults is 7 and 40 mg/day, respectively.^[28]

Cobalt concentrations ranged between 0.31 to 2.0 mg kg^–1 with a mean value of 0.59 ± 0.43 mg kg^–1. Cobalt concentrations in the literature have been reported in the range of 0.02–0.67 mg kg^–1 for muscles of fish from internal markets of India^[8] and 0.0–0.10 mg kg^–1 from the USA.^[10] Our cobalt levels were slightly higher with the literature values. Cobalt is an essential nutrient for humans and is an integral part of vitamin B₁₂. Exposure to high levels of cobalt can result in lung and heart effects and dermatitis.^[27]

Chromium concentrations ranged between 0.329 and 1.38 mg kg^–1 with a mean value of 0.71 ± 0.26 mg kg^–1. In the literature, chromium contents in fish have been reported in the range of 0.07–1.48 mg kg^–1 from Turkey^[25] and 0.23–0.37 mg kg^–1 from Sweden.^[29] The average human requires an estimated 1 µg/day of chromium.^[35] Deficiency of chromium results in impaired growth and disturbances in glucose, lipid, and protein metabolism. There is no upper tolerable intake level for chromium according to the Institute of Medicine but the AI of chromium for women and mday, respectively/day, respectively.^[28,^29]

Strontium is a non-essential element because of its unknown metabolic functions in organisms. The element can be used as a marker to distinguish between fish and meat due to the fact that its concentration is considerably higher in fish than in meat.^[36] Strontium concentrations in this study were low, ranging between 0.3 to 0.864 mg kg^–1. These values coincide with the usual concentration found in seafoods 0.37–1.8 from Serbia.^[26] Vanadium concentrations in the yellowfin tuna samples ranged between 0.11 to 0.66 mg kg^–1 with a mean value of 0.29 ± 0.17 mg kg^–1. Vanadium concentrations were reported in the range of 0.97–1.35 mg kg^–1 from Iran^[37] and 0.0–0.3mg kg^–1 from the USA.^[10] There are no available data on the carcinogenicity of vanadium in humans.^[27] The UL of vanadium for adults is 1.8 mg/day and there are no data available for other age groups.^[28]

Toxic metals

Cadmium values in this study were ranged from < 0.01 to 0.116 with an average of 0.016 ± 0.03 mg kg^–1 (Table 1). Cadmium levels in the literature were < 0.01–0.04 mg kg^–1 for muscles of fish in southeastern Aegean Sea, Turkey,^[38] 0.02–1.32 mg kg^–1 for muscles of fish from internal markets of India^[8] and 0.01–1.0 mg kg^–1 for muscles of fish from the Arabian Sea, Oman.^[9] Humans are exposed to cadmium through food and the average daily intake for adults has been determined by expert FAO/WHO as Provisional Tolerable Weekly Intake (PTWI). PTWI for cadmium is 7 µg per week kg^–1 body weight. For a person with body weight 70 kg is 490 µg per week.^[39] Maximum cadmium levels in the muscles in this study were found to be lower than the EU limit of 0.1 mg kg^–1 for cadmium.^[40]

The muscle tissue of yellowfin tuna shows the low contamination level for lead and was ranged from not detectable to 0.298 mg kg^–1 with the mean of 0.029 ± 0.082 mg kg^–1. Lead in the literature have been reported in the range of 0.33–0.93 mg kg^–1 for muscles of fish from Black sea^[33] and 0.02-1.43 mg kg^–1 for muscles of fish from the Arabian Sea, Oman.^[40] The PTWI for an adult is 25 µg per week kg^–1 body weight. For a person with a body weight of 70 kg is 1750 µg per week.^[39] The permissible lead concentration for fish is 0.3 mg kg^–1 according to the EU standards.^[41]

Mercury concentration in the yellowfin tuna muscle varied from 0.036 to 0.447 mg kg^–1 wet weight with a mean of 0.137 ± 0.09 mg kg^–1. All the samples had concentrations of mercury below the 1.0 mg kg^–1 wet weight limit recommended by the EU.^[41,^40] The results of our study (0.137 ± 0.09 mg kg^–1) are in agreement with the levels (0.15 ± 0.10 mg kg^–1) reported by Alfredo et al.^[11] for the same species from the Mexican waters, but higher than those reported by Garcıa-Hernandez et al.^[42] for the Gulf of California for this same species (0.03 mg kg^–1). In this study, none of the yellowfin tuna had a mercury content (1 mg kg^–1) that exceeded the EU and Omani legislations.

Fatty Acids and Nutritional Indexes

The content of fatty acids in yellowfin tuna samples was measured and expressed as mg of fatty acids per 100 g of wet tissue. The distribution of saturated (SFA), monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA) in the muscle of yellowfin tuna is shown in Table 2. The species showed higher levels of PUFA than SFA and MUFA. Similar result was obtained by Khan et al.^[43] for kingfish from different coastal regions of the Sultanate of Oman. Among saturated fatty acids, palmitic acid (C16:0) was the dominant one (118.8 mg 100g^–1 tissue) followed by stearic acid (C18:0) 41.5 mg 100g^–1. The fatty acid 18:1 n-9 (Oleic acid) was the dominant MUFA and the mean value was 54.36 mg 100g^–1 tissue. The predominance of 16:0 in SFA and 18:1n-9 in MUFA was also revealed by other authors in various marine and fresh water fish species.^[23,44–48] Whereas 22:6 n-3 (DHA) was the dominant polyunsaturated fatty acid (148.2 mg 100 g^–1 tissue) among PUFAs. Similar pattern was described by Guiler et al.^[49] for zander and carp muscle lipids in Altinapa Dam Lake. Among the n-6 fatty acids, arachidonic acid (20:4n-6) was the dominant fatty acid (14.38 mg 100 g^–1) followed by linoleic acids (18:2n6c) with 6.52 mg 100 g^–1. These results matched with Gorgun et al.^[50] who reported that arachidonic acid was the most abundant n6 fatty acids in some major tissues of Vimbavimbain Egridir Lake, Turkey. The n-3 fatty acids accounted for between 67.9 and 13.45% of the PUFAs, of which DHA (148.28 mg 100 g^–1 tissue) and EPA (29.35 mg 100 g^–1tissue) were the most abundant. Similarly, Cakmak et al.^[51] reported that DHA was found to be the major polyunsaturated fatty acids in the muscle lipids of five different fish species. As shown in Table 2 the PUFA/SFA and n-3/n-6 ratio were over 1.1 and 5.78, respectively. These ratios are generally used for assessing the nutritional value of fat. A balanced intake of n-6 and n-3 PUFAs is essential for health.^[39] Nutritional recommendations have been made in order to increase the levels of PUFA and n-3 PUFA to ensure that the ratio PUFA/SFA and n3/n-6 is not less than 0.45 and 0.25, respectively.^[53]Taking into account the daily EPA+DHA intake recommendation of 250 mg^[3] for adult male and non-pregnant/non lactating female, the consumption of yellowfin tuna may be advised. For pregnant and lactating female, the minimum intake for optimal health and fetal and infant, development is 300 mg per day EPA/DHA, of which at least 200 mg per day should be DHA.^[3] Also, EPA and DHA intakes have demonstrated physiological benefits on blood pressure, heart rate, triglycerides, likely inflammation, endothelial function, cardiac diastolic function, and consistent evidence for a reduced risk of fatal CHD and sudden cardiac death at consumption of ~250 mg per day of EPA plus DHA.^[54] When a woman with 60 kg body weight consumes an average 100 g fresh yellowfin tuna per day, yellowfin tuna would provide 71.05 and 74% of daily required EPA+DHA and DHA, respectively (Table 3). Hence, the consumption of yellowfin tuna may be advised. The current EFSA opinion^[7] took into account recent developments in epidemiological studies indicate that n-3 long-chain PUFA in fish may counteract the negative effects from methyl-mercury exposure. Based on the value obtained for mercury (0.130 mg kg^–1) it can be concluded that the intake of mercury is not of major health concern in the population. Thus, low-mercury fish yellowfin tuna would be one of the best options for those that frequently consume tuna fish to get sufficient EPA plus DHA. Regarding the thrombogenic and atherogenic potential of fish, the low thrombogenic (0.27) and atherogenic (0.43) index values were below the TI and AI indices values of 0.30 and 0.51, respectively proposed by Ulbricht and Southgate.^[16] The TI and AI index for the yellowfin tuna is similar to that reported for silver scabbard fish, hake, ray,^[19] and raw mackerel.^[16] However, relatively higher AI values for anchovies, cod,^[55] rays;^[44] high AI and TI values for raw Mediterranean fish are also reported.^[56] The value obtained for h/H index (1.97) indicates that regular intake of yellowfin tuna may bring about a hypocholesterolemic effect. The h/H index value obtained for the yellowfin tuna is comparable to that calculated for hake (h/H = 1.92) by Afonso et al.^[19] However, relatively higher h/H values are reported by these authors for silver scabbard fish (2.60) and ray (2.19).

TABLE 2 Fatty acid profile of yellowfin tuna (mean ± standard deviation)

Fatty acid (mg 100 g^−1 tissue)	Mean	SD
Capric Acid Methyl Ester (C10:0)	0.849	0.399
Undecanoic Acid Methyl Ester (C11:0)	0.168	0.160
Lauric Acid Methyl Ester (C12:0)	0.825	0.428
Tridecanoic Acid Methyl Ester (C13:0)	1.065	0.631
Myristic Acid Methyl Ester (C14:0)	10.84	6.50
Pentadecanoic Acid Methyl Ester (C15:0)	3.677	2.567
Palmitic Acid Methyl Ester (C16:0)	118.8	56.40
Heptadecanoic Acid Methyl Ester (C17:0)	4.871	2.182
Stearic Acid Methyl Ester (C18:0)	41.51	12.54
Arachidic Acid Methyl Ester (C20:0)	3.322	2.522
Behenic Acid Methyl Ester (C22:0)	0.659	0.407
Tricosanoic Acid Methyl Ester (C23:0)	3.686	2.42
Lignoceric Acid Methyl Ester (C24:0)	0.301	0.254
Others	5.90	3.01
Σ SFA	196.56	68.17
Myristoleic Acid Methyl Ester (C14:1)	0.236	0.137
cis-10-Pentadecenoic Acid Methyl Ester (C15:1)	0.726	0.579
Palmitoleic Acid Methyl Ester (C16:1)	11.02	4.33
cis-10-Heptadecenoic Acid Methyl Ester (C17:1)	2.666	1.174
Elaidic Acid Methyl Ester (C18:1n9t)	11.101	6.94
Oleic Acid Methyl Ester (C18:1n9c)	54.36	22.81
cis-11-Eicosenoic Acid Methyl Ester (C20:1)	3.070	1.333
Erucic Acid Methyl Ester (C22:1n9)	1.679	1.340
Σ MUFA	84.87	34.5
Linolelaidic Acid Methyl Ester (C18:2n6t)	0.857	0.816
Linoleic Acid Methyl Ester (C18:2n6c)	6.528	5.805
Gamma-Linolenic Acid Methyl Ester (C18:3n6)	3.271	3.261
Linolenic Acid Methyl Ester (C18:3n3)	3.670	2.707
cis-11,14-Eicosadienoic Acid Methyl Ester (C20:2)	1.729	1.605
cis-8,11,14-Eicosatrienoic Acid Methyl Ester (C20:3n6)	2.337	1.523
cis-11,14,17-Eicosadienoic Acid Methyl Ester (C20:3n3)	4.626	2.242
Arachidonic Acid Methyl Ester (C20:4n6)	14.384	7.00
cis-13,16-Docosadienoic Acid Methyl Ester (C22:2)	3.043	2.139
cis-5,8,11,14,17-Eicosapentaenoic Acid Methyl Ester (C20:5n3)	29.35	13.64
cis-4,7,10,13,16,19-Docosahexaenoic Acid Methyl Ester (C22:6n3)	148.28	64.4
Σ PUFA	218.09	86.05
Σn3	185.2
Σn6	32.15
n3/n6	5.783
PUFA/SFA	1.10
DHA/EPA	5.052
TI	0.27
AI	0.43
h/H	1.97

SFA = Saturated fatty acid; MUFA = Monounsaturated fatty acid; PUFA = Polyunsaturated fatty acid/

TABLE 3 Dietary evaluation by consuming 100 g of the yellowfin tuna fish

Constituent	Recommended or typical daily intake	Yellowfin tuna
Protein (g)	91^a	24.82
Total fat (g)	65^a	2.88
Energy (K cal)	2000^a	302
SFA (g)	17^a	0.196
MUFA (g)	24^a	0.084
PUFA (g)	20^a	0.218
n-3 (PUFA mg)	300^b	185.9
DHA (mg)	200^c	148.2

^aDietary Guidelines for Americans (2005).

^bAHA (2003).^[4]

^cWHO (2008).^[3]

Conclusions

Based on the lipid content yellowfin tuna may be considered as a low fat fish. In addition, the fish seems to be a good source of macro elements, especially K and Na, and the micro element’s contents observed in the range of provisional tolerable daily intake amounts recommended by FAO and WHO for a 60 kg person. The observed values of heavy metals were below the permissible limits issued by the FAO/WHO for human consumption. Moreover, the fish is rich in unsaturated fatty acid in particular to PUFA such as ARA, DHA, and EPA. To get sufficient EPA plus DHA without exceeding the reference dose of mercury, yellowfin tuna would be good options for pregnant and lactating women due to the lower levels of heavy metals.

ACKNOWLEDGMENTS

The authors would like to thank Mrs. Nada Al-Abri of Fishery Quality Control Center, Oman, for her constant assistance and contribution in sample preparation during this project.

FUNDING

The fund provided for this project number 1/3/25 by the Agriculture and Fisheries Development Fund (AFDF) is greatly acknowledged.

Additional information

Funding

The fund provided for this project number 1/3/25 by the Agriculture and Fisheries Development Fund (AFDF) is greatly acknowledged.