Ingredient evidence library
What actually works, by the research
Plain-English summaries of what each supplement ingredient does, what the human trials really show, and the dose studied — each with an A–D evidence-strength grade from our published, transparent rubric.
Research snapshot35ingredients graded54sources cited5categories
Longevity
See rankings →| Ingredient | What it’s for | Evidence | Studied dose | Studies |
|---|---|---|---|---|
| Nicotinamide Riboside (NR) | NAD+ precursor intended to restore age-related decline in cellular NAD+. | AStrong | 250-1000 mg/day (up to 2000 mg/day studied); reliably raises NAD+ | 2 |
| Coenzyme Q10 (CoQ10) | Mitochondrial electron-transport cofactor and lipophilic antioxidant; declines with age. | BModerate | 100-200 mg/day (often paired with selenium in the trial); ubiquinol better absorbed | 2 |
| Nicotinamide Mononucleotide (NMN) | NAD+ precursor one step closer to NAD+ than NR; aimed at restoring NAD+ pools. | BModerate | 250-900 mg/day; ~600 mg/day cited as a practical upper-efficacy point for NAD+/performance | 2 |
| Resveratrol | Polyphenol and putative sirtuin (SIRT1) activator; popularized by the 'red wine' longevity hypothesis. | BModerate | Highly variable in trials (~150 mg up to 1000-1500 mg/day); no consensus longevity dose | 1 |
| Spermidine | Naturally occurring polyamine that induces autophagy; epidemiologically linked to lower mortality. | BModerate | ~1 mg/day used (likely sub-therapeutic); optimal supplemental dose undefined | 1 |
| Urolithin A | Gut-derived metabolite that stimulates mitophagy (clearance of damaged mitochondria) to support mitochondrial and muscle health. | BModerate | 500-1000 mg/day (Mitopure form) for 2-4 months in trials | 2 |
| Fisetin | Plant flavonoid investigated as a senolytic to clear senescent ('zombie') cells. | DPreliminary | Mouse-derived intermittent dosing (~20 mg/kg/day for 2-3 days) used in trials; no established human regimen | 1 |
Nootropics & focus
See rankings →| Ingredient | What it’s for | Evidence | Studied dose | Studies |
|---|---|---|---|---|
| Bacopa monnieri | Ayurvedic herb whose bacoside saponins are thought to enhance cholinergic signaling and synaptic transmission, improving memory consolidation with chronic use. | AStrong | 300-450 mg/day of a standardized extract (about 55% bacosides), taken for at least 8-12 weeks. | 1 |
| Caffeine + L-theanine | Caffeine blocks adenosine receptors for alertness; L-theanine (an amino acid in tea) increases alpha brain-wave activity and blunts caffeine's jitteriness. | AStrong | Roughly 50-100 mg caffeine paired with 100-200 mg L-theanine (about a 1:2 ratio) per dose, as used in most trials. | 1 |
| Citicoline (CDP-choline) | An intermediate in phosphatidylcholine synthesis that supplies choline for acetylcholine and supports neuronal membrane integrity. | BModerate | 250-500 mg/day; the strongest trial used 500 mg/day for 12 weeks. | 1 |
| Lion's Mane (Hericium erinaceus) | Edible mushroom whose hericenones and erinacines may stimulate nerve growth factor (NGF) synthesis, theoretically supporting neuronal health. | BModerate | Commonly 1.8-3 g/day of fruiting-body extract in trials; no consensus effective dose for healthy adults. | 1 |
| Rhodiola rosea | Adaptogenic herb whose rosavins and salidroside are proposed to modulate the stress-response (HPA axis) and reduce fatigue-related cognitive decline. | BModerate | Roughly 288-680 mg/day of a standardized extract (often SHR-5) for 2-6 weeks in fatigue trials. | 1 |
| L-Tyrosine | A dietary amino acid that serves as a precursor for dopamine and noradrenaline, helping replenish catecholamines depleted by acute stress. | CLimited | Trials commonly used 100-150 mg/kg (roughly 7-12 g for an adult) as a single acute dose before a stressor; lower daily doses are unproven. | 2 |
| Alpha-GPC (choline alphoscerate) | A choline-donating phospholipid that crosses the blood-brain barrier and serves as a precursor for the memory-related neurotransmitter acetylcholine. | DPreliminary | 400-1200 mg/day in clinical trials (commonly 600 mg/day); benefit in healthy users is unproven. | 1 |
Sleep
See rankings →| Ingredient | What it’s for | Evidence | Studied dose | Studies |
|---|---|---|---|---|
| Magnesium (glycinate) | Essential mineral that modulates NMDA/GABA-A receptor activity and the HPA stress axis; deficiency is associated with poorer sleep. | AStrong | Trials used 320-729 mg elemental magnesium/day; common practical dosing is ~200-400 mg elemental magnesium in the evening (adult RDA ~310-420 mg). | 1 |
| Apigenin (chamomile) | Flavonoid (the main active in chamomile) that binds benzodiazepine sites on GABA-A receptors, producing mild anxiolytic/sedative effects. | BModerate | Human chamomile trials used ~200-560 mg extract/day; isolated apigenin sleep doses (~50 mg) are popular online but not validated by clinical trials. | 1 |
| L-theanine | Amino acid from tea that promotes relaxation by increasing alpha brain-wave activity and modulating GABA, dopamine, and serotonin without sedation. | BModerate | 200 mg/day (range ~200-400 mg), often taken in the evening. | 2 |
| Melatonin | Endogenous pineal hormone that signals biological night and advances the sleep-wake (circadian) phase via MT1/MT2 receptors. | BModerate | 0.5-5 mg taken ~30 min to 3 h before bedtime; dose-response data suggest efficacy peaks around 4 mg, but lower doses (0.5-1 mg) are often sufficient and more physiologic. | 1 |
| Valerian (Valeriana officinalis) | Herbal root extract thought to act on GABA-A receptors and adenosine signaling to produce mild sedation. | BModerate | 300-600 mg of root extract taken ~30-120 minutes before bedtime; trial doses ranged roughly 225-1,215 mg/day. | 2 |
| Glycine | Inhibitory amino-acid neurotransmitter that lowers core body temperature (via NMDA receptors in the suprachiasmatic nucleus), promoting sleep onset. | CLimited | 3 g taken ~30-60 minutes before bedtime. | 2 |
Testosterone
See rankings →| Ingredient | What it’s for | Evidence | Studied dose | Studies |
|---|---|---|---|---|
| Ashwagandha (Withania somnifera root extract) | Adaptogen that lowers cortisol and stress signaling, with downstream support of the hypothalamic-pituitary-gonadal axis. | BModerate | 300 mg standardized root extract once or twice daily (about 21 mg withanolide glycosides/day, or ~5% withanolides), for at least 8 weeks. | 1 |
| Boron | Trace mineral proposed to lower sex hormone-binding globulin (SHBG) and estradiol, modestly raising free (bioavailable) testosterone. | BModerate | About 6-10 mg/day of elemental boron in the studied protocols; NIH notes no established requirement, with a tolerable upper limit of 20 mg/day for adults. | 1 |
| D-Aspartic Acid (DAA) | Amino acid that may stimulate luteinizing hormone and testicular testosterone release via the hypothalamic-pituitary-gonadal axis. | BModerate | Studied at 3-6 g/day; higher doses (6 g/day) have been associated with reduced rather than increased testosterone in trained men, so it is not recommended for this purpose. | 2 |
| Fenugreek (Testofen / Trigonella foenum-graecum seed extract) | Furostanol saponins may modestly support androgenic activity and partially inhibit aromatase and 5-alpha-reductase. | BModerate | 500-600 mg/day of a standardized seed extract such as Testofen (about 50% fenusides/saponins), for 8-12 weeks. | 2 |
| Vitamin D (cholecalciferol, D3) | Steroid hormone precursor; vitamin D receptors are expressed in testicular and pituitary tissue, suggesting a permissive role in androgen production. | BModerate | Correct deficiency to a serum 25(OH)D of ~30 ng/mL; trials showing effects used roughly 3,000-5,000 IU/day for 12+ weeks. NIH RDA is 600-800 IU/day; tolerable upper limit 4,000 IU/day for adults. | 2 |
| Zinc | Essential cofactor for testicular steroidogenesis and gonadotropin signaling; deficiency impairs testosterone synthesis. | DPreliminary | Roughly 30 mg/day of elemental zinc has been used in correction studies; NIH RDA is 11 mg/day for adult men, with a tolerable upper limit of 40 mg/day. Avoid chronic high doses (copper depletion risk). | 2 |
Weight loss
See rankings →| Ingredient | What it’s for | Evidence | Studied dose | Studies |
|---|---|---|---|---|
| Garcinia cambogia (HCA) | Tropical fruit extract supplying hydroxycitric acid (HCA), claimed to block fat synthesis and suppress appetite. | AStrong | Marketed at roughly 1,500-3,000 mg/day HCA, but no dose is established as both effective and safe; liver-injury reports are not clearly dose-dependent. | 3 |
| Berberine | Plant alkaloid that activates AMPK; studied for blood sugar, lipids and modest weight reduction — popularized online as "nature's Ozempic," a comparison the evidence does not support. | BModerate | Trials commonly use 900-1,500 mg/day split into 2-3 doses with meals; GI tolerance and drug interactions limit higher intake. | 2 |
| Caffeine | Stimulant that modestly raises energy expenditure and fat oxidation and can blunt appetite short-term. | BModerate | Commonly 100-400 mg/day in trials; effects appear dose-dependent, but tolerance develops and >400 mg/day raises side-effect risk. | 1 |
| Capsaicin (capsaicinoids) | Pungent chili compound that activates TRPV1 receptors, modestly raising thermogenesis and reducing appetite. | BModerate | Roughly 2-6 mg capsaicinoids per day in trials (>=2 mg appears needed to reduce energy intake). | 2 |
| CLA (conjugated linoleic acid) | Family of linoleic-acid isomers marketed for fat loss; proposed to reduce fat storage and increase fat oxidation. | BModerate | Studies typically use about 3.2 g/day; higher intakes raise GI and metabolic side-effect concerns without added benefit. | 2 |
| Fiber (soluble / psyllium) | Viscous, gel-forming soluble fiber that slows digestion and increases satiety to support lower energy intake. | BModerate | Roughly 5-15 g/day of psyllium (often divided before meals); general soluble-fiber intake of 10 g+/day in trials. | 2 |
| Glucomannan | Viscous soluble fiber from konjac that swells in the stomach to increase fullness and slow gastric emptying. | BModerate | About 3 g/day (often 1 g three times daily before meals) with adequate water, as used in trials. | 2 |
| Green tea extract (EGCG) | Catechin (EGCG) that, especially with caffeine, modestly stimulates thermogenesis and fat oxidation. | BModerate | Catechin doses around 270-1200 mg/day (EGCG often 100-460 mg/day), typically combined with caffeine, over 12+ weeks. | 1 |
| L-carnitine | Transports long-chain fatty acids into mitochondria for oxidation; theorized to support fat metabolism. | BModerate | Around 2,000 mg/day, where dose-response modeling suggested the maximal effect in adults. | 1 |