Vitamin B1, B2, B3, B5, B6, B12, B15, etc

The Science of the B Vitamins: An Evidence-Tiered Summary Table

TL;DR

The clearest, RCT-proven uses of every B vitamin are correcting their own deficiency diseases (beriberi/Wernicke-Korsakoff for B1, pellagra for B3, megaloblastic/pernicious anemia for B9 and B12, seborrheic-type dermatitis for B7), plus a short list of well-proven "extra" indications: riboflavin (B2) for migraine prophylaxis, niacin (B3) for dyslipidemia and nicotinamide for non-melanoma skin cancer chemoprevention, B6 for nausea of pregnancy, folic acid for neural-tube-defect prevention, and myo-inositol for PCOS.
Most other marketed benefits (energy, mood, cognition, hair/nails, cardiovascular disease prevention) remain "suspected" only — supported by observational/mechanistic data or mixed/failed trials. Notably, large RCTs (AIM-HIGH, HPS2-THRIVE) showed niacin adds no cardiovascular benefit on top of statins, and homocysteine-lowering with B vitamins has not reliably prevented cardiac events.
RDAs are small (roughly 1.1–16 mg or 2.4–400 mcg for the essential Bs), but typical OTC supplement doses often greatly exceed them. Watch three specific safety issues: B6 sensory neuropathy at chronic high doses, niacin flushing/liver injury at gram doses, and folic acid masking B12 deficiency. Choline and inositol have Adequate Intakes or no formal value; PABA, "B15," and "B17" are not true vitamins ("B17"/laetrile is dangerous).

Key Findings

How to read the evidence tiers

Column 1 (PROVEN by RCT): treatment effects demonstrated in randomized controlled trials or meta-analyses of RCTs, or the unambiguous reversal of a classical deficiency disease (an effect so consistent it constitutes proof even though modern placebo-controlled trials would be unethical).
Column 2 (SUSPECTED): observational associations, mechanistic rationale, or preliminary/mixed/negative trial evidence.
Column 3 (US RDA/AI): Institute of Medicine / National Academies / NIH Office of Dietary Supplements values.
Column 4 (typical OTC dose): the dose ranges commonly found in multivitamins and B-complex supplements, per NIH ODS fact sheets — distinct from high therapeutic/prescription doses.

Summary table (condensed)

Vitamin	Col 1 — PROVEN (RCT / deficiency reversal)	Col 2 — SUSPECTED (obs./mechanistic/mixed)	Col 3 — US RDA/AI (adults)	Col 4 — Typical OTC dose
B1 Thiamine	Beriberi (dry/wet), Wernicke-Korsakoff; ↑LV function in systolic HF (meta-analysis of small RCTs)	Cognition/Alzheimer's; diabetic complications; sepsis/critical illness	M 1.2 / F 1.1 mg (preg 1.4); no UL	~1.5 mg (multi); 50–100 mg (B-complex)
B2 Riboflavin	Ariboflavinosis; migraine prophylaxis 400 mg/d (Schoenen 1998; AAN Level B)	Cataract; MTHFR-related BP/homocysteine; anemia	M 1.3 / F 1.1 mg (preg 1.4; lact 1.6); no UL	1.3 mg (multi); 50–100 mg (B-complex)
B3 Niacin	Pellagra; dyslipidemia (gram doses); nicotinamide 500 mg BID → −23% non-melanoma skin cancer (ONTRAC)	CV prevention on statins (disproven: AIM-HIGH, HPS2-THRIVE); skin cancer in transplant pts (ONTRANS negative)	M 16 / F 14 mg NE (preg 18); UL 35 mg	~16–20 mg (multi); ≥500 mg (niacin-only); Rx 500–2,000 mg
B5 Pantothenic acid	Reverses experimental deficiency	Acne (high-dose); wound healing (pantothenol); lipids (pantethine)	AI 5 mg (preg 6; lact 7); no UL	~10 mg (multi) up to 1,000 mg
B6 Pyridoxine	Deficiency (dermatitis/anemia/seizures); nausea of pregnancy (ACOG 1st-line, ± doxylamine); isoniazid antidote	PMS; carpal tunnel (mostly negative); cognition/mood; CV via homocysteine	1.3 mg (19–50); M>50 1.7; F>50 1.5 mg; UL 100 (EFSA 12)	~1.7 mg (multi); 50–100 mg (B-complex)
B7 Biotin	Biotin deficiency; biotinidase deficiency	Hair/skin/nails w/o deficiency (weak); MS (mixed/negative)	AI 30 mcg (lact 35); no UL	30–60 mcg (multi); 5,000–10,000 mcg (hair/nail)
B9 Folate	Megaloblastic anemia; NTD prevention (MRC 1991, −72%)	Stroke (modest, region-dependent); cognition (negative); depression adjunct; cancer-risk signal at high dose	400 mcg DFE (preg 600; lact 500); UL 1,000 mcg folic acid	400–800 mcg
B12 Cobalamin	Pernicious anemia & B12-deficiency states; high-dose oral = IM (RCTs)	Fatigue/energy w/o deficiency (unsupported); cognition (negative); CV via homocysteine	2.4 mcg (preg 2.6; lact 2.8); no UL	5–25 mcg (multi); 500–1,000 mcg (standalone)
Choline	Reverses deficiency fatty liver/muscle damage	NAFLD; fetal neurodevelopment (promising); cognition; TMAO/CV concern	AI M 550 / F 425 mg (preg 450; lact 550); UL 3,500 mg	Often absent in multis; ~250–550 mg standalone
Inositol (myo-)	PCOS ~4 g/d (multiple RCTs/meta-analyses)	IVF/fertility; GDM prevention (mixed; MYPP 2025 negative); panic/OCD (high-dose)	None (not essential)	2–4 g/d (often 40:1 with D-chiro)
PABA ("B10")	Peyronie's disease (1 RCT, POTABA 3 g QID) — not a true vitamin	Scleroderma (weak/negative); vitiligo; graying hair	None	300–400 mg therapeutic; trace in some B-complex
"B15" pangamic / "B17" laetrile	None — not vitamins; laetrile → cyanide, no anticancer efficacy	None credible	None	Avoid

B1 — Thiamine

PROVEN (RCT/deficiency): Reverses/prevents beriberi (dry = peripheral neuropathy; wet = high-output heart failure) and Wernicke-Korsakoff syndrome/Wernicke encephalopathy; these classical deficiency diseases respond dramatically to thiamine (typically IV boluses ~500 mg for acute Wernicke, tapering to 100 mg oral; wet beriberi can improve within ~12 hours). A meta-analysis of small double-blind, placebo-controlled RCTs (DiNicolantonio et al., Ochsner Journal 2013) found thiamine improved left-ventricular function in systolic heart failure patients.
SUSPECTED: cognition/Alzheimer's disease (mechanistic; human evidence limited); diabetic complications; critical-illness/sepsis outcomes; hyperemesis-related deficiency prevention.
RDA: Adult men 1.2 mg/day; women 1.1 mg/day (pregnancy/lactation 1.4 mg). No UL (no established toxicity; median US intake ~2 mg/day from food).
Typical OTC dose: ~1.5 mg in multivitamins; 50 mg ("B-50") to 100 mg ("B-100") in B-complex/standalone products.

B2 — Riboflavin

PROVEN (RCT/deficiency): Reverses ariboflavinosis (angular stomatitis, cheilosis, sore throat, seborrheic dermatitis). Migraine prophylaxis: the landmark double-blind RCT by Schoenen, Jacquy & Lenaerts (Neurology 1998;50:466–470, n=55) found that at 400 mg/day, 59% of the riboflavin group vs 15% of placebo were "responders" (≥50% reduction in attack frequency), P=0.002, number-needed-to-treat 2.3, with superiority on attack frequency (P=0.005) and headache days (P=0.012). Riboflavin is rated Level B by the American Academy of Neurology; systematic reviews find effects more consistent in adults than children.
SUSPECTED: cataract prevention; adjunct in some inborn errors of metabolism; effect-modifier of MTHFR-related hypertension/homocysteine; anemia correction.
RDA: Adult men 1.3 mg/day; women 1.1 mg/day (pregnancy 1.4 mg; lactation 1.6 mg). No UL.
Typical OTC dose: Multivitamins commonly 1.3 mg (100% DV); B-50/B-100 complexes 50–100 mg.

B3 — Niacin (nicotinic acid / niacinamide / nicotinamide)

PROVEN (RCT/deficiency): Reverses/prevents pellagra (dermatitis, diarrhea, dementia). Dyslipidemia: gram-doses of nicotinic acid raise HDL-C and lower LDL-C/triglycerides, and the pre-statin Coronary Drug Project showed niacin reduced myocardial infarction (~27%) and stroke. Non-melanoma skin cancer chemoprevention: the ONTRAC phase 3 RCT (Chen AC et al., NEJM 2015;373:1618–1626, n=386) found nicotinamide 500 mg twice daily produced a 23% lower rate of new non-melanoma skin cancers (95% CI 4–38; P=0.02) in high-risk immunocompetent patients over 12 months.
SUSPECTED / DISPROVEN as add-on: Cardiovascular event prevention on top of statins — the large HPS2-THRIVE RCT (Armitage et al., NEJM 17 July 2014, n=25,673) found adding extended-release niacin/laropiprant did not reduce major vascular events (rate ratio 0.96, 95% CI 0.90–1.03, P=0.29) and caused significant excess diabetes, infection, GI, musculoskeletal, and bleeding events; AIM-HIGH (n=3,414) likewise showed no benefit. Niacin is therefore no longer recommended as a statin add-on. Skin-cancer prevention in organ-transplant recipients failed in the ONTRANS RCT (2023).
RDA: Adult men 16 mg NE/day; women 14 mg NE/day (pregnancy 18 mg NE; lactation 17 mg NE; 1 NE = 1 mg niacin = 60 mg tryptophan). UL 35 mg/day (from supplements/fortified foods, based on flushing).
Safety: Nicotinic acid causes prostaglandin-mediated flushing (even at ~75 mg); gram doses and extended-release forms can cause hepatotoxicity and raise blood glucose. Niacinamide/nicotinamide does not cause flushing.
Typical OTC dose: ~16–20 mg in multivitamins; niacin-only supplements often 500 mg or more per serving; prescription ER niacin 500–2,000 mg.

B5 — Pantothenic Acid

PROVEN (deficiency): Reverses experimental deficiency (rare; features numbness/burning feet, fatigue, GI symptoms). No robust RCT-proven therapeutic use beyond deficiency.
SUSPECTED: acne (some preliminary high-dose trials); wound healing (pantothenol; limited data); lipid effects (the derivative pantethine).
AI (no RDA): Adults 5 mg/day (pregnancy 6 mg; lactation 7 mg). No UL (very high doses, e.g., 10,000 mg, cause GI upset/diarrhea).
Typical OTC dose: ~10 mg in multivitamins up to 1,000 mg in B-complex/standalone products (per NIH ODS).

B6 — Pyridoxine / Pyridoxal-5-phosphate (P5P)

PROVEN (RCT/deficiency): Reverses deficiency (dermatitis, glossitis, microcytic anemia, infant seizures). Nausea and vomiting of pregnancy: RCTs (e.g., Sahakian et al. 1991, 25 mg every 8 h, n=59) show pyridoxine reduces nausea; B6 (often combined with doxylamine, as Diclegis/Diclectin) is an ACOG-recommended first-line therapy. Standard antidote for isoniazid toxicity and certain seizures.
SUSPECTED: premenstrual syndrome (some positive but low-quality trials); carpal tunnel syndrome (largely negative); cognition/mood; cardiovascular risk via homocysteine (not proven).
RDA: Adults 19–50: 1.3 mg/day; men >50: 1.7 mg; women >50: 1.5 mg (pregnancy 1.9 mg; lactation 2.0 mg). US UL 100 mg/day; EFSA (2023) set a much lower UL of 12 mg/day based on neuropathy data.
Safety: Chronic high-dose pyridoxine causes sensory peripheral neuropathy (reported across 100–6,000 mg/day, with cases even at lower prolonged doses). PLP/P5P is the active form, but the UL applies to total B6 from all sources — a key point for anyone stacking B-complex, energy drinks, and fortified foods.
Typical OTC dose: ~1.7 mg (DV) in multivitamins; 50–100 mg in B-50/B-100 complexes and standalone products.

B7 — Biotin (vitamin H)

PROVEN (deficiency): Reverses biotin deficiency (hair loss, scaly periorificial dermatitis, conjunctivitis, neurological symptoms) and treats biotinidase deficiency (an inborn error of metabolism).
SUSPECTED: hair/skin/nail improvement in people without deficiency (popular but weakly supported); multiple sclerosis (high-dose 300 mg/day trials mixed/negative); brittle nails.
AI (no RDA): Adults 30 mcg/day (lactation 35 mcg). No UL.
Safety: High-dose biotin (≥1 mg, especially 5–10 mg) causes clinically dangerous interference with immunoassays (thyroid tests, troponin, hormones), risking misdiagnosis; the FDA has warned that even a single 10-mg dose can distort results within 24 hours. This is a laboratory-safety hazard, not classical toxicity.
Typical OTC dose: 30–60 mcg in multivitamins; hair/skin/nail products commonly 5,000–10,000 mcg (5–10 mg).

B9 — Folate / Folic Acid / Methylfolate (5-MTHF)

PROVEN (RCT/deficiency): Corrects megaloblastic (folate-deficiency) anemia. Neural tube defect prevention: the MRC Vitamin Study (Lancet 1991;338:131–137, n=1,817) showed 4 mg folic acid periconceptionally cut NTD recurrence by 72% (relative risk 0.28, 95% CI 0.12–0.71); mandatory US fortification (since 1998) has substantially reduced NTDs. Folic acid reliably lowers homocysteine.
SUSPECTED / MIXED: Stroke — a 2024 meta-analysis of 21 RCTs (115,559 participants, Clinical Nutrition) found folic acid reduced stroke risk by 10% (RR 0.90, 95% CI 0.83–0.98), but the benefit was concentrated in non-fortified/partially-fortified regions (RR 0.83) and absent where grain is already fortified (RR 1.04; P-interaction=0.003). Cognition/dementia (trials lower homocysteine but do not improve cognition); depression adjunct; and a possible increased cancer risk signal at high doses (colorectal, prostate, bladder — from some RCTs/observational data, e.g., the Norwegian trials showing +21% cancer incidence).
RDA: Adults 400 mcg DFE/day; pregnancy 600 mcg DFE; lactation 500 mcg DFE. Women who could become pregnant: 400 mcg folic acid/day. UL 1,000 mcg/day of synthetic folic acid (food folate is unrestricted).
Safety: High folic acid can mask B12 deficiency (correcting the anemia while neurological damage progresses) — hence the 1,000 mcg limit and the advice to rule out B12 deficiency before high-dose folate.
Typical OTC dose: 400–800 mcg (as folic acid or 5-MTHF) in multivitamins/prenatals and standalone products.

B12 — Cobalamin (methyl- / cyano- / hydroxo-)

PROVEN (RCT/deficiency): Treats pernicious anemia and other B12-deficiency states (megaloblastic anemia, subacute combined degeneration of the cord, peripheral neuropathy). RCTs (Kuzminski et al. 1998; Berlin et al. 1968) show high-dose oral B12 (1,000–2,000 mcg/day) is as effective as intramuscular injection for pernicious anemia, via ~1% passive absorption independent of intrinsic factor. Corrects deficiency in vegans, older adults with atrophic gastritis, and post-bariatric/malabsorption patients.
SUSPECTED: fatigue/energy in non-deficient people (not supported); cognition/dementia (trials negative despite homocysteine lowering); cardiovascular prevention via homocysteine (not proven).
RDA: Adults 2.4 mcg/day (pregnancy 2.6 mcg; lactation 2.8 mcg). No UL (very low toxicity; half-life >350 days).
Typical OTC dose: 5–25 mcg in multivitamins; 50–500 mcg in B-complex; 500–1,000 mcg in standalone B12 supplements (per NIH ODS). Cyanocobalamin is the most common form.

Extended / quasi-B-complex members

Choline

PROVEN (deficiency): Choline deprivation causes hepatic steatosis (fatty liver) and muscle damage, reversed by choline; it was recognized as an essential nutrient in 1998.
SUSPECTED: NAFLD prevention/treatment (a large cross-sectional Chinese study of ~56,000 adults links low intake to NAFLD; mechanistic support strong, but RCT evidence in biopsy-confirmed disease is limited); fetal brain/neurodevelopment and pregnancy outcomes (promising animal and human data; the AMA and AAP endorse adequate maternal intake, but definitive RCT proof of clinical endpoints is lacking); cognition. Choline-derived TMAO is a possible cardiovascular-risk concern.
AI (no RDA): Men 550 mg/day; women 425 mg/day (pregnancy 450 mg; lactation 550 mg). UL 3,500 mg/day. The majority of Americans fall below the AI (mean intakes ~310–315 mg/day).
Typical OTC dose: Often absent from standard multivitamins; standalone/combination products commonly provide ~250–550 mg (as choline bitartrate, phosphatidylcholine, or lecithin). High intakes cause fishy body odor, sweating, and hypotension.

Inositol (myo-inositol)

PROVEN (RCT): Polycystic ovary syndrome (PCOS) — multiple RCTs and meta-analyses (including a 2023 review of 26 RCTs, n≈1,691) show myo-inositol ~4 g/day improves ovulation, menstrual regularity, insulin sensitivity, and androgen levels, with efficacy comparable to metformin and fewer side effects. Inositol is not an essential vitamin (the body synthesizes it; there is no deficiency disease).
SUSPECTED / MIXED: IVF/fertility oocyte quality (positive meta-analyses); gestational diabetes prevention (several positive Southern-European RCTs showing 58–60% lower GDM, but the 2025 MYPP trial in pregnant PCOS women was negative for the composite of GDM/preeclampsia/preterm birth); panic disorder and OCD (high-dose 12–18 g/day, preliminary).
RDA/AI: None established (not classified as an essential nutrient; no NIH ODS fact sheet).
Safety/interactions: Well tolerated even at high doses; additive with diabetes drugs; possible interaction with lithium at high doses.
Typical dose: 2–4 g/day myo-inositol (often in a 40:1 ratio with D-chiro-inositol for PCOS, e.g., Ovasitol); most-studied range 1–4 g/day.

PABA (para-aminobenzoic acid; "vitamin B10" / "Bx")

NOT a true vitamin / not essential — it is a folate precursor for bacteria, not for humans.
PROVEN (limited RCT): Peyronie's disease — a double-blind placebo-controlled trial (n=103) of potassium PABA (POTABA) 3 g four times daily significantly slowed disease progression (it did not shrink existing plaques). FDA-approved for Peyronie's disease and scleroderma, though the scleroderma evidence is weak-to-negative.
SUSPECTED: vitiligo, scleroderma skin-softening (a 30-year-old retrospective study), male infertility, graying hair — all weakly supported.
RDA: None (not essential).
Safety: Doses >8 g/day risk serious toxicity including liver injury; keep ≤400 mg/day without medical supervision. Formerly a sunscreen UV filter, now largely abandoned due to allergy and fabric staining.
Typical OTC dose: Small amounts in some B-complex/multivitamins; therapeutic dosing ~300–400 mg/day.

"B15" (pangamic acid) and "B17" (laetrile / amygdalin) — NOT vitamins

Neither is a vitamin, an essential nutrient, nor a recognized therapeutic agent. "Pangamic acid" has no defined chemical identity; the FDA formally deems pangamic acid products unsafe for food and drug use (CPG 457.100).
"B17"/laetrile/amygdalin is dangerous: it is metabolized to cyanide, has caused documented cases of cyanide poisoning, and the National Cancer Institute plus a 1982 NEJM clinical trial (n=178) found no anticancer efficacy. It is not a vitamin — the "B17" label was a marketing device to evade drug regulation. The FDA has issued warning letters against sellers. Avoid entirely.
No RDA; no legitimate supplement dose.

Details

The deficiency diseases are the bedrock of proof. For every essential B vitamin, the single most rigorously established "treatment" is correction of its own deficiency syndrome. These effects predate modern RCT methodology but are causally airtight: beriberi and Wernicke encephalopathy (B1), ariboflavinosis (B2), pellagra (B3), deficiency dermatitis/anemia/seizures (B6), biotin-deficiency dermatitis and biotinidase deficiency (B7), megaloblastic anemia and neural-tube defects (B9), and pernicious anemia/subacute combined degeneration (B12). Under a rigorous evidence-tiering framework, all of these belong firmly in Column 1.

Beyond deficiency, only a short list of B-vitamin uses meets an RCT bar: riboflavin 400 mg for migraine prevention (Schoenen 1998; AAN Level B); nicotinic acid for dyslipidemia and nicotinamide 500 mg BID for non-melanoma skin cancer (ONTRAC); pyridoxine for nausea of pregnancy (ACOG first-line); high-dose oral B12 for pernicious anemia; folic acid for NTD prevention (MRC 1991); and myo-inositol ~4 g/day for PCOS.

The cardiovascular story is a cautionary tale about mechanism-versus-outcome. B vitamins reliably lower homocysteine, and observational data linked homocysteine to vascular disease — but the large homocysteine-lowering RCTs (HOPE-2, VISP, NORVIT, SEARCH) largely failed to reduce cardiac events, and the niacin add-on trials (AIM-HIGH, HPS2-THRIVE) were negative with added harms. Stroke is the one endpoint where meta-analyses hint at a benefit (10%, RR 0.90), but that benefit is concentrated in primary-prevention populations in countries without folic-acid fortification and disappears where grain is fortified — a textbook "suspected, partly proven only in specific contexts" area.

Safety and upper limits deserve emphasis for a supplement-taking audience:- B6: sensory neuropathy from chronic high intake; the US UL is 100 mg/day but the EFSA (2023) UL is only 12 mg/day, and neuropathy has occurred within that gap — a key point for anyone taking B-50/B-100 complexes long-term.- Niacin: flushing (nicotinic acid), and hepatotoxicity plus hyperglycemia at gram doses/extended-release; UL 35 mg/day.- Folic acid: masking of B12 deficiency; UL 1,000 mcg/day; possible cancer-promotion signal at high doses.- Biotin: immunoassay interference at ≥1–10 mg — a laboratory-safety (not toxicity) hazard.- Choline: fishy body odor, hypotension, and a possible TMAO/cardiovascular concern at high doses; UL 3,500 mg/day.

Recommendations

In the table, split each vitamin's Column-1 cell into "deficiency disease (proven)" and "other RCT-proven indication (if any)." This preserves the crucial distinction between "fixes its own deficiency" and "treats an unrelated condition," which is where most public confusion lives.
Flag the four "marketing vs. evidence" gaps explicitly in Column 2: energy/fatigue (no benefit without deficiency), hair/skin/nails (biotin — weak), cognition/dementia (repeatedly negative trials despite homocysteine lowering), and cardiovascular prevention (negative/mixed). These are the most over-claimed benefits.
Give Column 4 (typical dose) as a range with a "multivitamin vs. standalone" split, because the spread is enormous (e.g., B12 5–25 mcg in a multi vs. 1,000 mcg standalone; pantothenic acid 10 mg vs. 1,000 mg). Anchor these to NIH ODS language.
Add a dedicated safety column or footnote for B6 (neuropathy; note the 12-vs-100 mg/day UL disagreement), niacin (flushing/liver), folic acid (B12 masking), and biotin (lab interference). These are the actionable risks for supplement users.
Treat choline and inositol as "conditionally B-complex" with AI/no-value labels, and quarantine PABA, "B15," and "B17" in a clearly-labeled "not true vitamins" row — with an explicit poison warning on laetrile/"B17."

Thresholds that would change these recommendations: a well-powered replication of ONTRAC would harden nicotinamide's skin-cancer indication; a positive large RCT of choline for biopsy-confirmed NAFLD would move choline's liver indication into Column 1; and any adequately powered myo-inositol RCT with live-birth (rather than surrogate) endpoints would upgrade or downgrade its fertility claims. Conversely, the region-dependence of the folate–stroke effect means new data from fortified populations would not change the conclusion that fortification has already captured most of the benefit.

Caveats

Deficiency-reversal as "proof": For ethical reasons, modern placebo-controlled RCTs of, e.g., thiamine for beriberi do not exist; the evidence is historical and mechanistic but causally definitive. I have counted these as "proven" while labeling the evidence type.
Combination-trial confounding: Many B-vitamin trials use multi-nutrient combinations (folate + B6 + B12), making single-vitamin attribution difficult, especially for homocysteine/cardiovascular/cognition endpoints.
Dose ranges are approximate and market-dependent: OTC formulations vary widely by brand and change over time; the figures reflect NIH ODS descriptions and common "B-50/B-100" conventions, not a specific product survey.
Inositol and choline are not classical B vitamins; inositol has no RDA/AI and choline has only an AI. Their inclusion follows the request to cover extended/quasi-B-complex members.
Source hierarchy: All deficiency, RDA/AI, UL, and pivotal-trial facts are anchored to NIH Office of Dietary Supplements fact sheets, the National Academies/IOM DRI reports, Cochrane/meta-analyses, or primary NEJM/JAMA/Lancet/Neurology trial reports. Some secondary sources (supplement references, health-content sites) were used only to characterize typical marketed doses and claims.

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