The Role of Dietary Ingredients in Mental Energy – A Scoping Review of Randomized Controlled Trials

Figures & data

Table 1. Potential mode of action in mental energy for the dietary ingredients evaluated.

Ingredient	Biological classification	Potential active ingredient(s)	Potential modes of action	Reference(s) for review
Ashwagandha	Withania somnifera	Withaferin A Sitoindosides Withanosides	Anti-inflammatory Cyclooxygenase‐2 and α2-macroglobulin inhibition Brain-derived neurotrophic factor exacerbation	Ng et al. (21)
Blueberries	Vaccinium Cyanococcus	Anthocyanidins Flavanols Flavonols	Inducible NO synthase downregulation Cyclooxygenase-2 downregulation Inhibit cytokine release Reactive oxygen species downregulation Tumor necrosis factor α downregulation	Hein et al. (22) Spencer (23) Henriques et al. (24)
Chamomile	Matricaria chamomilla	Flavonoids Apigenin	GABA-A receptor activation	Avallone et al. (25) Srivastava et al. (26)
Citrus	Citrus	Auraptene Flavonoids	Anti-inflammatory Reduce oxidative stress Neuroprotection	Galluzzi et al. (27) Matsuzaki et al. (28)
Cordyceps mushroom	Cordyceps	Cordycepin	Brain-derived neurotrophic factor increase Tropomyosin receptor B increase	Cai et al. (29)
Dark chocolate	Theobroma cacao	Flavonoids Methylxanthines	Nitric oxide increase Brain-derived neurotrophic factor increase Adenosine receptor inhibition	Yoneda et al. (30) Katz et al. (31) Smit et al. (32)
Ginseng^2	Panax	Ginsenosides	Reduce catecholamine secretion Neuroprotection Reduce oxidative stress Anti-inflammatory Neurogenesis and plasticity enhancement	Lee et al. (33) Feng et al. (34)
Green tea	Camellia sinensis	Catechins Theanine	Reduce oxidative stress Neuroprotection Monoaminergic pathway regulation	Schmidt et al. (35) Afzal et al. (36) Rao et al. (37)
Guarana	Paullinia cupana	Methylxanthines Flavonoids Anthocyanidins	Neuroprotection Reduce oxidative stress	Torres et al. (38)
Lavender^3	Lavandula	Terpenes Flavonoids	NMDA receptor antagonism Serotonin transporter inhibition	Lopez et al. (39)
Licorice root	Glycyrrhiza glabra	Glycyrrhizins Flavonoids	T/B cell proliferation Neuroprotection	Jiang et al. (40) Cho et al. (41)
Lion’s mane mushroom	Hericium erinaceus	Hericenones Erinacines	Increased nerve growth factor synthesis Neuroprotection	Kawagishi et al. (42) Ma et al. (43)
Maca	Lepidium meyenii	Alkaloids Isothiocynates Glucosinolates Polysaccharides	Improve mitochondrial function Upregulate autophagy proteins Reduce oxidative stress Neuroprotection	Guo et al. (44) Zha et al. (45) Pino-Figueroa et al. (46)
Melatonin foods	Various	Melatonin	Reduce oxidative stress Anti-inflammatory Improve mitochondrial function Circadian regulation	Salehi et al. (47) Meng et al. (48)
Mint	Mentha	Polyphenols	Reduce oxidative stress Anti-inflammatory Anticholinesterase activity	Fallarini et al. (49) Mushtaq et al. (50) Rocha et al. (51)
Reishi mushroom	Ganoderma	Terpenes Polysaccharides	Reduce oxidative stress Neuroprotection	Lee et al. (52) Huang et al. (53)
Turmeric	Curcuma longa	Polyphenols Curcuminoids	Reduce oxidative stress Anti-inflammatory Improve mitochondrial function Anticholinesterase activity Monoaminergic pathway regulation Brain-derived neurotrophic factor increase	D’Cunha et al. (54) Ak et al. (55) Lopresti et al. (56)
Valerian root	Valeriana officinalis	Valerenic acid Valepotriates Sesquiterpenes	GABA receptor antagonism Serotonin receptor agonist	Yuan et al. (57) Dietz et al. (58) Diaper et al. (59)

GABA: gamma-aminobutyric acid; NO: nitric oxide; NMDA: N-methyl-D-aspartate.

Table 2. Search term strategy and records result summary.

Ingredient	Ingredient search terms^a	Mental energy terms	Records screened (n)	Full-text articles assessed (n)	Full-text articles included (n)
Ashwagandha	Withania somnifera, ashwagandha, Indian ginseng, poison gooseberry, winter cherry	brain, cognition, cognitive, fatigue, motivation, mood, affect, energy, vigor, memory, speed, attention, anxiety, calm, vigilance, enthusiasm, determination, sustained attention, mental energy, cognitive performance, mental performance, alert, mental fatigue, sleepiness, tired	16	7	5
Blueberries	blueberry, cyanococcus		57	4	4
Chamomile	chamomile, chamomilla, recutita, camomile, chamaemelum, anthemis, matricaria		33	4	2
Citrus	orange, citrus, citrus, fruit, citrus sinensis		351	18	8
Cordyceps mushroom	caterpillar fungus, caterpillar mushroom, champignon chenille, cordyceps sinensis, cordyceps		9	1	0
Dark chocolate	dark chocolate, cacao, cocoa, cocoa extract, cocoa flavanol, theobromine, theobroma cacao		617	27	16
Ginseng^b	ginseng, panax, ginsenoside		167	29	13
Green tea	green tea, theanine, catechin, matcha, epigallocatechin gallate, EGCG, camellia sinensis		429	23	13
Guarana	guarana, paullinia cupana		24	13	3
Lavender^c	lavender, lavandula, silexan		76	7	4
Licorice root	licorice, glycyrrhiza glabra, licorice		46	0	0
Lion’s mane mushroom	lion’s mane mushroom, hericium erinaceus, hou tou gu, yamabushitake		3	3	3
Maca	maca, lepidium meyenii		15	3	2
Melatonin foods	tart cherry, goji berry, walnut, berry, nut, pistachio, almonds, grain, corn, pineapple, tomato, banana, orange, ginger root, mustard seed, corn, rice, bean, food AND melatonin		45	7	5
Mint	mint, spearmint, mentha		106	14	6
Reishi mushroom	reishi, lingzhi, ganoderma lingzhi, ganoderma lucidum		15	3	1
Turmeric	turmeric, curcumin, curcuma, curcuma domestica, curcuma longa, curcuminoids		212	11	7
Valerian root	valeriana, valeriana officinalis, valerian root, valerian, baldrian		40	16	9

^a Each group of ingredient terms was combined with the mental energy terms for the PubMed database literature search (see also Supplemental Material).

^b The term “Indian ginseng” was excluded from this search.

^c The terms “inhale” and “aroma” were excluded from this search.

Table 3. PICOS table for inclusion of studies.

Parameter	Criteria
Population (P)	Healthy and non-healthy adults (male and female), $\ge$18 years of age, and without any diagnosis of severe disease except for diabetes and metabolic dysfunction (e.g., cancer, autoimmune disease, neurologic disorders, major mental illness)
Intervention (I)	Dietary intervention studies which included an ingredient as the intervention, not solely measured as part of a dietary pattern or administered via ingestion
Comparison (C)	Placebo or no intervention
Outcome (O)	A mental energy related outcome^a
Study design (S)	Randomized controlled trials

^a Refer to Table 1 for mental energy terms included in the search term strategy.

Figure 1. Summary of distribution of cognition tests categorized by domain.

Table 4a. Total number of improved mental energy outcomes for each dietary ingredient.

Mental energy outcome^a	Ashwagandha	Blueberry	Chamomile	Citrus	Dark chocolate	Ginseng	Green tea	Guarana
Cognition: Attention and concentration
Total number improved outcomes (n)	3	0	0	1	14	7	5	0
Total outcomes (n)	4	4	0	7	31	45	27	4
Total improved outcomes (%)	75%	0%	–	14%	45%	16%	19%	0%
Cognition: Executive functions
Total improved outcomes (n)	1	1	0	1	6	5	0	0
Total outcomes (n)	1	8	0	9	10	24	8	0
Total improved outcomes (%)	100%	13%	–	11%	60%	21%	0%	–
Cognition: General cognition
Total improved outcomes (n)	0	0	0	1	1	0	0	0
Total outcomes (n)	0	0	0	2	7	0	0	0
Total improved outcomes (%)	–	–	–	50%	14%	–	–	–
Cognition: Language
Total improved outcomes (n)	0	0	0	0	0	0	0	0
Total outcomes (n)	0	0	0	0	0	0	1	0
Total improved outcomes (%)	–	–	–	–	–	–	0%	–
Cognition: Memory
Total improved outcomes (n)	0	1	0	1	1	4	0	0
Total outcomes (n)	0	14	0	8	18	9	9	2
Total improved outcomes (%)	–	7%	–	13%	6%	44%	0%	0%
Cognition: Visuospatial skills
Total improved outcomes (n)	0	0	0	0	0	3	0	0
Total outcomes (n)	0	0	0	0	1	6	0	2
Total improved outcomes (%)	–	–	–	–	0%	50%	–	0%
Mood and perceived feelings
Total improved outcomes (n)	9	1	0	2	6	9	4	0
Total outcomes (n)	13	8	2	18	55	62	45	12
Total improved outcomes (%)	69%	13%	0%	11%	11%	15%	9%	0%
Sleep
Total improved outcomes (n)	5	0	6	1	0	0	3	0
Total outcomes (n)	8	0	10	1	0	1	7	2
Total improved outcomes (%)	63%	–	60%	100%	–	0%	43%	0%
Overall cognition^b
Total improved outcomes (n)	4	2	0	4	22	19	5	0
Total outcomes (n)	5	26	0	26	67	84	45	8
Total improved outcomes (%)	80%	8%	–	15%	33%	23%	11%	0%

^a Relevant outcomes evaluated in each study were categorized into mood and perceived feelings, sleep, or cognition groups. Cognition outcomes were further subcategorized into six cognitive domains as described in Figure 1. The total (n and percent) statistically significant improved outcomes and total number of outcomes evaluated are provided by category and ingredient.

^b Improved and total outcomes for overall cognition are the sum of the six cognitive domains.

Table 4b. Total number of improved mental energy outcomes for each dietary ingredient (continued).

Mental energy outcome^a	Lavender	Lion’s mane mushroom	Maca	Melatonin foods	Mint	Reishi mushroom	Turmeric	Valerian root
Cognition: Attention and concentration
Total number improved outcomes (n)	0	0	0	0	3	0	1	0
Total outcomes (n)	0	0	0	0	25	0	8	21
Total improved outcomes (%)	–	–	–	–	12%	–	13%	0%
Cognition: Executive functions
Total improved outcomes (n)	0	0	0	1	3	0	1	0
Total outcomes (n)	0	0	0	6	10	0	3	0
Total improved outcomes (%)	–	–	–	17%	30%	–	33%	–
Cognition: General cognition
Total improved outcomes (n)	0	2	0	0	0	0	0	0
Total outcomes (n)	0	2	0	1	0	0	1	0
Total improved outcomes (%)	–	100%	–	0%	–	–	0%	–
Cognition: Language
Total improved outcomes (n)	0	0	0	0	0	0	0	0
Total outcomes (n)	0	0	0	0	0	0	2	0
Total improved outcomes (%)	–	–	–	–	–	–	0%	–
Cognition: Memory
Total improved outcomes (n)	0	0	0	0	0	0	1	0
Total outcomes (n)	0	2	0	19	16	0	7	5
Total improved outcomes (%)	–	0%	–	0%	0%	–	14%	0%
Cognition: Visuospatial skills
Total improved outcomes (n)	0	0	0	0	0	0	0	0
Total outcomes (n)	0	0	0	0	2	0	1	0
Total improved outcomes (%)	–	–	–	–	0%	–	0%	–
Mood and perceived feelings
Total improved outcomes (n)	5	0	6	0	3	0	17	0
Total outcomes (n)	8	2	7	16	48	1	38	37
Total improved outcomes (%)	63%	0%	86%	0%	6%	0%	45%	0%
Sleep
Total improved outcomes (n)	0	0	0	11	2	0	0	9
Total outcomes (n)	1	1	0	24	20	0	0	37
Total improved outcomes (%)	0%	0%	–	46%	10%	–	–	24%
Overall cognition^b
Total improved outcomes (n)	0	2	0	1	6	0	3	0
Total outcomes (n)	0	4	0	26	53	0	22	26
Total improved outcomes (%)	–	50%	–	4%	11%	–	14%	0%

^a Relevant outcomes evaluated in each study were categorized into mood and perceived feelings, sleep, or cognition groups. Cognition outcomes were further subcategorized into six cognitive domains as described in Figure 1. The total (n and percent) statistically significant improved outcomes and total number of outcomes evaluated are provided by category and ingredient.

^b Improved and total outcomes for overall cognition are the sum of the six cognitive domains.

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