Clinical Summary
Vitamin B3 is a family of four clinically distinct compounds that share one destination (NAD+/NADP+) but diverge in pharmacology, safety, and indication:
- Niacin (nicotinic acid) — GPR109A agonist; causes cutaneous flushing; historically used for dyslipidemia but definitively abandoned after HPS2-THRIVE (2014) and Cochrane 2017 showed no cardiovascular benefit. The 2024 Hazen/Ferrell Nature Medicine paper identified niacin's terminal metabolite 4PY as causally driving endothelial VCAM-1 and atherosclerosis risk — a mechanistic explanation for the null/harm observed in cardiovascular trials.
- Nicotinamide (niacinamide) — Amide form; no GPR109A activation, no flushing, no glucose dysregulation; well-tolerated to 3 g/day. The strongest evidence-to-practice match in the entire B3 family is the ONTRAC trial (500 mg BID prevents recurrent non-melanoma skin cancer in immunocompetent high-risk adults).
- Nicotinamide Riboside (NR) — Reliably raises blood NAD+ (5/5 surrogate endpoint) but nine years of RCTs have failed to translate this into clinical outcomes for metabolic, cognitive, or sarcopenia endpoints. Narrow 2024-2025 positive signals in COPD, PAD, Werner syndrome, and plasma pTau-217 keep the hypothesis alive.
- Nicotinamide Mononucleotide (NMN) — Smaller Western trial base; Japanese consumer market-dominant; FDA reinstated supplement status after 3-year exclusion. Raises NAD+ comparably to NR but three 2024-2025 meta-analyses show no effect on glucose, lipids, or muscle function. Christen 2026 Nat Metab revealed both NR and NMN rely on gut microbial conversion to nicotinic acid for NAD+ elevation — collapsing mechanistic product differentiation.
Who benefits most: (1) patients with deficiency (pellagra, alcoholism, isoniazid therapy, celiac, extensive small-bowel resection) — definitive repletion; (2) immunocompetent adults with history of ≥2 non-melanoma skin cancers — nicotinamide 500 mg BID; (3) patients considering niacin for lipids — don't. Everyone else is in WATCH territory: the longevity promise remains mouse-dominant, human surrogate-biased, and commercially hyped. "Pellagra is rare in wealthy nations" is the correct starting prior; everything beyond deficiency repletion is probabilistic.
Indications & Evidence
| Indication | Evidence | Type | BH | Safety | Effect Size | Population | Dose | Duration | Key PMID |
|---|---|---|---|---|---|---|---|---|---|
| Pellagra treatment | 5/5 | DC | 9 | -- | 100% response (historical) | All deficient | Nicotinamide 100 mg TID | 3-4 wk | 14693013 |
| Isoniazid-induced pellagra (prevention) | 5/5 | DC | 9 | -- | Prevents with B6+nicotinamide | INH-treated malnourished | Nicotinamide 50-100 mg + B6 25-50 mg | Duration of INH | 3451228, 35427527 |
| Non-melanoma skin cancer recurrence (immunocompetent) | 4/5 | PC | 7 | -- | NMSC -23% (ONTRAC) | ≥2 prior NMSC, healthy | Nicotinamide 500 mg BID | 12 mo | 26488693 |
| NMSC in solid-organ transplant recipients | 2/5 | RC | 3 | -- | Null (ONTRANS failed) | Kidney transplant recipients | Nicotinamide 500 mg BID | 12 mo | 36856616 |
| Blood NAD+ elevation (NR) | 5/5 | SE | 8 | -- | +40-150% dose-dependent | Healthy adults | NR 100-2000 mg/day | 2-12 wk | 29599478, 29184669 |
| Blood NAD+ elevation (NMN) | 4/5 | SE | 8 | -- | +11-38% | Healthy adults | NMN 250-1250 mg/day | 4-12 wk | 33888596, 36482258 |
| Insulin sensitivity (NMN, prediabetic postmenopausal women) | 2/5 | UCC | 3 | -- | Muscle-only improvement (N=25) | Prediabetic postmenopausal F | NMN 250 mg/day | 10 wk | 33888596 |
| Glucose/lipid improvement (NMN, general) | 1/5 | RC | 2 | -- | Null — 3 meta-analyses | Mixed adults | NMN 250-1200 mg/day | 4-16 wk | 39531138, 39116016, 39111741 |
| Muscle function / sarcopenia (NR+NMN ≥60 yo) | 1/5 | RC | 2 | -- | Null meta (no SMI/HGS/gait benefit) | Adults ≥60 | Mixed NR/NMN doses | Variable | 40275690 |
| Cognitive function (NR in MCI) | 1/5 | RC | 2 | -- | Null cognition; pTau-217 ↓ (biomarker) | MCI/SCD | NR 250-1000 mg/day | 8-12 wk | 36859743, 39817194 |
| COPD airway inflammation | 3/5 | PC | 4 | -- | IL-8 -52.6%, lasting 12 wk post | COPD ex-smokers | NR 2 g/day | 6 wk | 39548320 |
| Peripheral artery disease (6-min walk) | 3/5 | PC | 3 | -- | +17.6 m vs placebo | PAD | NR 1 g/day | 6 mo | 38871717 |
| Hypertension (NR, ambulatory BP) | 1/5 | RC | 2 | -- | Null (NR+Ex vs PBO+Ex) | Adults ≥55 | NR 1 g/day + walking | 6 wk | 40770531 |
| Werner syndrome (arterial stiffness, skin ulcer) | 3/5 | UCC | 3 | -- | CAVI ↓, ulcer area ↓ | Werner syndrome | NR 1 g/day | 26 wk crossover | 40459998 |
| Long-COVID cognition/fatigue | 1/5 | RC | 2 | -- | Null primary (24 wk, 2 g NR) | Long-COVID | NR 2 g/day | 24 wk | 41357333 |
| Glaucoma neuroprotection | 3/5 | PC | 4 | -- | Visual-field improvement (Ph2); Ph3 pending | OAG on IOP therapy | Nicotinamide 1.5-3 g/day ± pyruvate | 6-24 mo | 34792559, 32721104 |
| IBD (GPR109A anti-inflammatory) | 3/5 | ME | 3 | MON | Preclinical + observational | UC/Crohn's | Niacin 500-1000 mg divided | 8-12 wk | 24412617 |
| Parkinson's disease (NR, NADPARK) | 2/5 | UCC | 3 | -- | Cerebral NAD ↑, MDS-UPDRS ns | Early PD | NR 1 g/day | 30 d | NCT03568968 |
| Cardiovascular outcome reduction (niacin) | 5/5 null | RC | 9 | WARN | No MACE benefit + harm (4PY signal) | CVD risk/2° prevention | Niacin 1-2 g/day | Long-term | 28616955, 22085343, 25014686, 38374343 |
| Longevity / lifespan extension (human) | 1/5 | ME | 1 | -- | No human outcome data | Any | Any B3 form | Lifelong | — |
| Topical skin (pigmentation, acne, barrier) | 4/5 | PC | 6 | -- | Comparable to 4% hydroquinone / 1% clindamycin | Adults with NMSC/hyperpigmentation/acne | Topical niacinamide 2-10% | 8-12 wk | 40005371 |
Reading this table: Stars = evidence volume for THIS specific claim. Type = causal-relationship classification. BH = Bradford Hill /9. Safety = FAERS/trial signals specific to this indication pathway. One row = one decision.
Hard rule: Star rating never exceeds the causal-taxonomy ceiling (e.g., ME caps at 2/5; SE caps at 5/5 for replicated surrogate but cannot be upgraded to clinical outcome).
Type codes: DC=Direct causation | PC=Probable causal | UCC=Unreplicated causal | BC=Biomarker correlation | SE=Surrogate endpoint | ME=Mechanistic extrapolation | AHE=Animal→human | OA=Observational | RC=Refuted claim | CF=Confounded | FA=Folk/anecdotal | NE=No evidence
BH: 7-9 strong | 5-6 moderate | 3-4 weak | 1-2 speculative | 0 none
Safety flags: -- None | MON Monitor | WARN Signal documented — see Safety | AVOID Contraindicated
Prescribing
Dosing Table
| Population | Dose | Timing | Notes |
|---|---|---|---|
| Adults 19+ (RDA) | 16 mg NE M / 14 mg NE F | Any | 1 mg niacin = 60 mg tryptophan |
| Pregnancy | 18 mg NE | Any | Stay ≤35 mg UL; avoid NR/NMN (no data) |
| Lactation | 17 mg NE | Any | Prenatal vitamin covers |
| Pellagra (acute) | Nicotinamide 100 mg TID | With meals | 3-4 wk; GI improves 24-48h, skin 3-7d |
| Subclinical deficiency | Nicotinamide 50-100 mg/day | Morning | 2-4 wk then RDA |
| NMSC secondary prevention (immunocompetent) | Nicotinamide 500 mg BID | Morning + evening | Continuous; ONTRAC protocol |
| Isoniazid prophylaxis (malnourished) | Nicotinamide 50-100 mg + B6 25-50 mg | With INH | Duration of INH therapy |
| NAD+ repletion (healthy aging) | NR 300-1000 mg/day | Morning | 2-4 wk to steady state |
| NAD+ repletion (nicotinamide alternative) | Nicotinamide 250-500 mg/day | Morning | Cost-effective; weaker NAD+ rise than NR |
| Glaucoma neuroprotection (emerging) | Nicotinamide 1.5-3 g/day ± pyruvate 1.5 g/day | Divided BID | Phase-3 NAMinG pending 2027 |
| Dyslipidemia (historical) | DO NOT USE | — | Cochrane 2017 null + 2024 4PY harm mechanism |
Formulation Table
| Form | Bioavailability | When to Use | Cost (USD/mo) |
|---|---|---|---|
| Nicotinamide (niacinamide) | Near-complete | Default for most indications; pellagra, NMSC, NAD+ support | $3-8 |
| Niacin IR (nicotinic acid) | 100% | Niche: severe hypertriglyceridemia unresponsive to fibrates + statin; IBD GPR109A trial | $5-12 |
| Niacin ER (Niaspan Rx) | 100%, delayed | Avoid — marginal flushing benefit, lingering hepatotoxicity risk | $25-80 |
| Niacin SR (OTC slow-release) | 100%, extended | Avoid — highest hepatotoxicity; OTC "wax matrix" products | $10-18 |
| Inositol hexanicotinate ("no-flush niacin") | Poor (~20-40%) | Avoid — does not meaningfully release niacin (Meyers 2003) | $12-20 |
| Nicotinamide Riboside (Niagen) | 40-60% dose-dependent | NAD+ repletion where premium budget tolerable | $35-60 |
| Nicotinamide Mononucleotide (NMN) | 10-40% | Per preference; not superior to NR for NAD+ elevation | $40-80 |
| Topical niacinamide (2-10%) | N/A (local) | Hyperpigmentation, acne, barrier, post-procedure | $10-40 |
Condition-Specific Protocols
Non-Melanoma Skin Cancer Recurrence (Immunocompetent)
Evidence: 4/5 | Key PMID: 26488693 (ONTRAC) + 40498148 (Hwang 2025 SOTR cohort) + 35134311 (Mainville meta)
Phase 1: Initiation (Weeks 1-2)
- Nicotinamide 500 mg once daily to establish tolerance
- Confirm no history of sustained-release niacin or daily high-dose (>3 g) use
- Discuss with dermatologist — this is adjunct to surveillance, not replacement
Phase 2: Therapeutic (Months 1-12)
- Nicotinamide 500 mg BID (morning + evening) with meals
- Continue standard dermatology follow-up every 6 months
- Expected: ~23% reduction in new NMSC (BCC or SCC) vs placebo
- AE profile matches placebo in ONTRAC — minimal monitoring
Phase 3: Maintenance (Month 12+)
- Continue 500 mg BID indefinitely if well-tolerated — benefit disappears after cessation per ONTRAC post-hoc
- Reassess annually; consider discontinuation if no new NMSC for 3+ years and low-risk skin phenotype
Drug Interaction Timing: No clinically meaningful spacing required at 1 g/day. If on carbamazepine/phenytoin, no documented interaction but monitor. Expected Outcomes: ~1 fewer NMSC per ~5 high-risk patients per year; no effect on melanoma Stop/Reassess Criteria: LFT elevation >2× ULN (unexpected at this dose); new finding of solid-organ transplant (benefit does not extend — ONTRANS 2023 null); pregnancy
IMPORTANT CAVEAT: Allen 2023 NEJM (PMID 36856616) found nicotinamide 500 mg BID did NOT reduce NMSC in kidney transplant recipients. The 2026 Tan/Williams reappraisal (PMID 41505062) flags population dependence. This protocol applies to IMMUNOCOMPETENT adults only.
Pellagra / Niacin Deficiency
Evidence: 5/5 | Key PMID: 14693013 (Hegyi review)
Acute pellagra (4Ds: dermatitis, diarrhea, dementia):
- Nicotinamide 100 mg TID × 3-4 weeks (oral; IM/IV if severe malabsorption)
- Add B-complex (often coexisting deficiencies)
- Response: diarrhea 24-48h → dermatitis 3-7d → cognition 7-14d (may be incomplete if chronic)
- Address underlying cause: alcoholism (FAERS + literature confirm), INH therapy, anorexia, malabsorption
Maintenance after acute: Nicotinamide 100 mg/day + dietary counseling (poultry, fish, legumes, enriched grains)
Isoniazid prophylaxis: Vitamin B6 25-50 mg/day (standard with INH); add nicotinamide 50-100 mg/day if malnutrition/alcoholism/low dietary niacin. Malawi 2017 pellagra outbreak during IPT scale-up established the need (PMID 35427527).
Safety
Interactions Table
| Interactant | Effect | Management |
|---|---|---|
| Statins | Additive hepatotoxicity + myopathy (niacin specific) | Avoid niacin-statin combination; nicotinamide/NR/NMN compatible |
| Diabetes medications | Niacin worsens glycemic control via GPR109A (+0.3-0.5% HbA1c) | Avoid niacin in diabetes; nicotinamide/NR/NMN safe (NMN may modestly improve in prediabetic F) |
| Isoniazid | Induces niacin deficiency (blocks B6-dependent Trp → niacin) | B6 25-50 mg + nicotinamide 50-100 mg daily during INH |
| Alcohol (chronic) | Depletes NAD+, impairs absorption, additive hepatotoxicity with niacin | Use nicotinamide 100-300 mg/day in chronic alcoholism; avoid niacin |
| Warfarin | Possible INR enhancement (niacin; inconsistent) | Monitor INR weekly ×4 weeks when initiating niacin |
| Anticonvulsants | Minimal; theoretical enzyme induction | Standard monitoring |
| Carbidopa/Levodopa | None documented | Standard |
| NR/NMN + exercise | Possible blunted training adaptation (rat data, PMID 32917636); negative human HTN+Ex trial (PMID 40770531) | Athletes: avoid high-dose NR/NMN during training cycles |
Contraindications
- Severe renal impairment (GFR <30) — metabolite accumulation risk, all forms
- Active liver disease / transaminases >3× ULN — all forms; niacin highest risk
- Active peptic ulcer disease — niacin only (stimulates gastric acid)
- Uncontrolled gout — niacin only (raises uric acid ~5-10%)
- Pregnancy/lactation + NR/NMN — no safety data; stay at RDA from prenatal vitamins
- Diabetes (any type) + niacin — use nicotinamide/NR/NMN instead
- Prior 4PY-signal cardiovascular risk (theoretical) — avoid high-dose niacin >500 mg/day in atherosclerotic disease
Adverse Effects (ranked by frequency)
Niacin (nicotinic acid) — genuine drug signal:
- Flushing (70-90% at ≥50 mg IR; 15-30 min onset; 30-60 min duration; tachyphylaxis in 1-2 wk)
- GI nausea/dyspepsia (5-12%)
- Hyperglycemia / HbA1c rise (10-20% at >1 g/day)
- Hyperuricemia / gout flare (5-10%)
- Hepatotoxicity (<1% IR; 3-10% SR at >1 g/day; 43 FAERS hepatic failure reports)
- Atrial fibrillation (small excess in HPS2-THRIVE / AIM-HIGH)
- Rare: macular edema, myopathy (with statins), fulminant hepatic failure (SR formulations)
Nicotinamide — supplement-noise pattern, no hepatotox/flushing signal up to ~3 g/day:
- GI nausea (5-10% at >1 g)
- Headache (uncommon)
- Rare reported LFT elevation at chronic >3 g/day (orthomolecular megadose territory)
NR — 32 total FAERS reports, no signal:
- Occasional nausea / GI (empty-stomach dosing)
- Sleep disruption if dosed late PM
- Headache rare
- No hepatotoxicity signal across 40+ completed trials to 2 g/day
NMN — 4 FAERS reports (all concomitant-role); no independent signal:
- Insomnia if dosed late (community-consistent)
- Mild GI (minority)
- Rare platelet/bruising case reports (low-N, unverified causality)
FAERS Signal Table (BioMCP, 2026-04-17)
| Reaction | FAERS Reports | Suspect Drug? | Seriousness | Linked Indication | Notes |
|---|---|---|---|---|---|
| Niacin — drug ineffective | 966 | Yes (99.9% suspect) | Low | CVD/lipid | Expected: Rx withdrawal from guidelines |
| Niacin — flushing | 393 | Yes | Mild | All niacin uses | Expected pharmacology (GPR109A) |
| Niacin — hepatic failure | 43 | Yes | Serious | All niacin uses | Concentrates in SR/ER formulations |
| Niacin — death-outcome reports | 245 | Yes | Fatal | Elderly polypharmacy | Co-terms: falls, pneumonia, renal/cardiac failure — confounded |
| Nicotinamide — all reactions | 5,953 | Variable | Low-moderate | Mixed | No flushing, no hepatotox, no death signal — supplement-noise pattern |
| NR — all reactions | 32 | Mostly concomitant | Low | — | Sample too small for signal detection |
| NMN — all reactions | 4 | All concomitant | — | — | No independent signal |
Reading FAERS data: Niacin's 13,483 reports with 99.9% suspect-drug assignment reflect its status as a prescription drug for decades — this is a genuine AE profile. Nicotinamide's 5,953 reports show the diffuse off-label-use/fatigue/nausea pattern typical of elderly polypharmacy confounding, not compound harm. NR and NMN FAERS absence reflects regulatory category (supplement not in FDA drug database), not safety endorsement.
Monitoring Table
| Test | When | Target |
|---|---|---|
| LFTs (AST/ALT/AP/bili) | Baseline + 6 wk + 12 wk for niacin >500 mg/day or nicotinamide >2 g/day | <3× ULN |
| Fasting glucose + HbA1c | Baseline + every 3 mo if on niacin | No HbA1c rise >0.3% |
| Uric acid | Baseline if gout history | No rise >1 mg/dL |
| Creatinine / eGFR | Baseline; annually if >60 yo or high-dose | Stable |
| CK (if on statins + niacin) | Baseline + if muscle symptoms | <10× ULN |
| Urinary N-methylnicotinamide | If suspected pellagra / subclinical deficiency | >0.8 mg/g creatinine |
Special Populations
Renal Impairment
| GFR Range | Dose Adjustment | Rationale | Evidence |
|---|---|---|---|
| 60-89 (mild) | Standard | Normal clearance | Moderate |
| 30-59 (moderate) | Reduce all forms by 50% | Metabolite accumulation (2PY, 4PY, N-methylnicotinamide) | Low |
| <30 (severe) | Avoid niacin; nicotinamide 100-250 mg only under supervision | 4PY accumulation particularly concerning post-Hazen 2024 | Low-moderate |
Hepatic Impairment
| Severity | Dose Adjustment | Rationale | Evidence |
|---|---|---|---|
| Child-Pugh A (mild) | Avoid niacin; nicotinamide/NR/NMN standard dose | Niacin-specific hepatotoxicity | Moderate |
| Child-Pugh B (moderate) | Avoid all forms >RDA until baseline LFTs stable | Reduced conjugation/methylation capacity | Low |
| Child-Pugh C (severe) | RDA from diet only | Decompensated liver cannot clear | Low |
Pregnancy & Lactation
- RDA 18/17 mg NE — covered by prenatal vitamin
- Nicotinamide: Category C (inconclusive); stay ≤35 mg UL from supplements
- NR, NMN: No safety data — avoid
- Niacin >35 mg/day during pregnancy: rare indication (severe hypertriglyceridemic pancreatitis); specialist only
Synergies & Stacking
| Co-nutrient | Why | Evidence |
|---|---|---|
| Vitamin B6 | Required cofactor for kynurenine pathway (Trp → niacin) | 5/5 biochemistry |
| Vitamin B2 | Kynurenine 3-monooxygenase cofactor | 4/5 biochemistry |
| Vitamin B12 + Folate | Support SAM regeneration for NNMT-mediated niacin methylation | 3/5 at mega-dose niacin |
| Tryptophan | Direct precursor (60:1 conversion); adequate protein reduces niacin need | 5/5 biochemistry |
| Pyruvate | Additive in glaucoma neuroprotection RCTs | 3/5 Ph2 (PMID 34792559) |
| Aspirin 325 mg | Blocks niacin flushing (COX → PGD2) when taken 30 min pre-dose | 3/5 mechanism |
| Trigonelline | Novel NAD+ precursor (coffee); Membrez 2024 Nat Metab | 2/5 emerging |
| NAD Plus (IV) | Shared endpoint; no NAD+ IV outcome trials exist (Gallagher 2026 PRISMA) | 2/5 surrogate only |
Antagonisms: alcohol (NAD consumption + hepatotoxicity), isoniazid (pellagra induction), high-dose SAM-e + mega-dose nicotinamide (methyl depletion theoretical).
Individual Response Modifiers
Sex-Specific Considerations
| Factor | Male | Female | Clinical Implication |
|---|---|---|---|
| Tryptophan → niacin conversion | Standard | Shifted toward serotonin during pregnancy / on oral contraceptives | Pregnant women/women on OCPs may have reduced endogenous niacin synthesis — prioritize dietary adequacy |
| NMN insulin-sensitivity benefit | No effect (Yoshino pilot null in men) | Benefit in prediabetic postmenopausal women (Yoshino 2021) | Sex-restricted single-trial signal — do not extrapolate to males |
| Niacin flushing intensity | Standard | Possibly more intense (estrogen-modulated PGD2) | Women may need slower titration; no formal RCT |
| Hepatotoxicity | Standard | Possibly higher baseline susceptibility | Monitor LFTs more frequently in women on niacin >1 g/day |
| Pregnancy/lactation + NR/NMN | N/A | No data; avoid | Use RDA from prenatal vitamin only |
| Study population bias | Most NR trials mixed | Yoshino NMN study women-only; most glaucoma trials mixed | Flag sex-restricted findings in evidence interpretation |
Genetic Modifiers
| Gene (SNP) | Variant | Effect on This Compound | Evidence | Action |
|---|---|---|---|---|
| Niacin-4PY pathway (rs10496731) | — | Higher 2PY/4PY levels → higher sVCAM-1 → MACE risk | GWAS (106k meta) + mendelian randomization, Ferrell 2024 PMID 38374343 | Hypothetical: carriers may have excess atherogenic risk from niacin — not clinically actionable yet but strengthens case against high-dose niacin |
| MTHFR (rs1801133) | C677T | Increased SAM demand for N-methylation at high-dose nicotinamide → may deplete methyl pool | Replicated biochemistry | TT homozygous + mega-dose nicotinamide (>2 g/day): ensure methylfolate + B12 |
| NNMT (various) | Multiple | Overexpression reduces NAD+ salvage; associated with neurodegeneration (Akl 2025 review PMID 40221009) | Preclinical; emerging | No human-actionable guidance yet — research only |
| Slc12a8 | — | Proposed NMN intestinal transporter (mouse); human relevance disputed (Christen 2026 reframes NR/NMN as gut-microbiota mediated) | Mouse + disputed human | Do not use Slc12a8 status as a reason to prefer NMN over NR |
| NAMPT variants | Low-activity | Reduced endogenous NAD+ salvage; carriers may benefit more from precursor supplementation | Research stage | Not clinically actionable |
No compound-relevant evidence for ABO/VWF, FUT2, APOE, VDR, COMT, BCMO1, CYP2D6/3A4, SOD2, SLC23A — these variants do not meaningfully alter Vitamin B3 response.
Community & Anecdotal Evidence
Disclaimer: Online community reports. Not clinical evidence. N-sizes approximate. Selection bias, placebo effect, and recall bias inherent.
Dominant Sentiment (by form)
- Niacin: Polarized. 50/50 "life-changed for my Lp(a)" vs "quit within a week from flush." Older, cardiology-adjacent, orthomolecular-overlapping. Low thousands of observable English voices.
- Nicotinamide: Strongly positive. Skincare dominates (tens of thousands); oral anti-anxiety / sleep secondary. The Ordinary 10% + Zinc 1% has tens of thousands of reviews.
- NR (Tru Niagen): Mixed-positive. Commercially dominant US. Low thousands of engaged longevity users. Older skew. "Safer bet than NMN."
- NMN: High enthusiasm / hype-cycle energy. Japanese consumer market massive (hundreds of thousands). English communities mid-thousands. Sinclair-driven.
What Users Report
| Reported Effect | Frequency | Typical Onset | Source Communities |
|---|---|---|---|
| Lipid changes (niacin) | Common — HDL↑, TG↓, Lp(a)↓ | 4-12 wk | Peter Attia listeners, cholesterol-focused subreddits |
| Flush discomfort → tolerance (niacin) | Common | 1-14 d | All niacin users |
| Skin hyperpigmentation / acne improvement (topical niacinamide) | Common | 8-12 wk | r/SkincareAddiction, r/AsianBeauty |
| Anti-anxiety (oral nicotinamide 500 mg – 1.5 g) | Moderate N | Same-day – 1 wk | Ray Peat / bioenergetic, nootropics |
| Sleep improvement (oral nicotinamide) | Majority positive; paradoxical minority | Same-night | LowToxinForum, Phoenix Rising |
| Energy (NMN > NR) | Moderate | 2-6 wk | r/longevity, r/Biohackers |
| Cognitive clarity (NMN, 40+) | Common in 40+; rare in 30s | 4-8 wk | Longecity, Sinclair ecosystem |
| Libido (NMN, 50+ men) | Moderate reports | 4-8 wk | Biohacker forums |
| Gray-hair "reversal" (NMN) | Small-N anecdote | Months | r/longevity — skeptical consensus |
| Insomnia if dosed late (NR/NMN) | Common | Same-night | All NAD+ communities |
| Joint mobility (NR long-term) | Small-N | 3-6 mo | Longecity long-term threads |
Community Dosing vs Clinical
| Source | Dose | Route | Notes |
|---|---|---|---|
| Clinical pellagra | 300 mg nicotinamide | Oral TID | 5/5 |
| Clinical NMSC | 500 mg BID nicotinamide | Oral | 4/5 ONTRAC |
| Clinical NR | 300-1000 mg | Oral AM | 4/5 |
| Community niacin (lipids) | 500-2000 mg IR | Titrated | Aggressive |
| Community megadose nicotinamide (orthomolecular) | 3-17 g | Oral divided | ️ hepatotox territory |
| Community NMN (biohacker) | 600-1000 mg | Oral AM | Sinclair's 1 g reference |
| Community NMN (Japan consumer) | 125-300 mg | Oral AM | Lower than Western |
| "Drug test detox" myth (niacin) | 3-5 g single dose | Oral | ️ ER visits documented |
Popular Stacks (Community)
| Stack Combination | Reported Purpose | Evidence Level |
|---|---|---|
| NR/NMN + TMG (trimethylglycine) | Offset methylation demand | 2/5 theoretical |
| NR + Pterostilbene (Elysium Basis) | "Sirtuin synergy" | 2/5 preclinical |
| NMN + Resveratrol (Sinclair protocol) | Longevity | 2/5 extrapolated from mice |
| Topical niacinamide + retinol + vitamin C | Skincare trifecta | 3/5 dermatology consensus (old "don't mix with C" myth debunked) |
| Niacin IR + aspirin 325 mg 30 min pre | Flush suppression | 3/5 mechanism-validated |
| Nicotinamide 1 g + magnesium + glycine | "Sleep stack" | 2/5 community |
Red Flags & Skepticism Notes
- MLM: Modere (Utah; shut down Apr 2024, acquired by Shaklee) sold adjacent anti-aging products but not NMN-focused. True MLM penetration of NR/NMN is minor — DTC/specialty retail dominates.
- Influencer concentration: David Sinclair (MetroBiotech co-founder — direct NMN drug-development conflict; disclosed but pervasive across media appearances), Charles Brenner (ChromaDex CSO — NR advocate with direct commercial interest), Rhonda Patrick (Tru Niagen affiliated), Dave Asprey (paid promotions), Ben Greenfield (affiliate structures). Peter Attia is notably skeptical of NR/NMN for healthy adults and does not take them.
- Astroturfing signals: Charava "What Reddit users say about NMN" = UK retailer commercial content masquerading as synthesis. Retailer SEO farms: omre.co, nmn.com, hello100.com, wonderfeel — all retailer-owned. "Clinically proven to raise NAD+ by X%" on virtually every NMN/NR label refers to surrogate PK endpoints, not clinical outcomes.
- Commercial bias: ChromaDex funds much of the NR trial base; Elysium funds separate subset (Norheim 2024 COPD); Sinclair's MetroBiotech funds key NMN trials (NCT05878119). Pencina 2023 JCEM (MIB-626) explicitly showed NAD+ rose but physical function did not — sponsor did not stop promoting.
- Quality scams: 2022-2024 Amazon NMN era saw many products assaying <10% of label. ChromaDex 2024 claims 87% of NR products miss label (conflicted source; same concern for NMN). Renue, Thorne, ProHealth, DoNotAge, Jinfiniti, NOVOS maintain COA transparency.
Folk vs Clinical Reality Check
Community experience ALIGNS with clinical data for: niacin lipid effects and flush tolerance development; topical niacinamide efficacy for skin; oral nicotinamide anxiolytic at ~1 g; sleep disruption from late-evening NR/NMN; NR at ~300 mg being broadly safe. Community experience DIVERGES from clinical data on: longevity/lifespan claims for NR/NMN (mouse data extrapolated, human outcome data absent), orthomolecular schizophrenia megadose (APA 1973 null + chronic hepatotox risk), "no-flush niacin" (IHN) being equivalent to niacin (Meyers 2003: it is not), NMN "reverses gray hair" (no objective data), and drug-test detox folklore (false + harmful). The most likely explanations for divergence are placebo (subjective energy/clarity highly susceptible), dosing disparities (community often 2-3× clinical), population differences (50+ self-selects into responder cohort), and stacking confounders (nearly no user takes just one B3 form).
Deep Dive: Mechanisms & Research
The four B3 forms converge on NAD+/NADP+, cofactors for >400 enzymes (glycolysis, TCA cycle, oxidative phosphorylation, PARP DNA repair, sirtuin deacetylation, CD38 consumption). NAD+ declines ~50-70% between ages 40-80 via increased CD38 and NADH oxidation. Three NAD+ biosynthesis routes exist: de novo (tryptophan → kynurenine, B6-dependent), salvage (nicotinamide → NMN → NAD+ via NAMPT, the rate-limiting step), and Preiss-Handler (nicotinic acid → NAMN → NAD+).
2026 paradigm shift (Christen Nat Metab, PMID 41540253): The first rigorous human head-to-head (n=65, 14 days) showed NR and NMN raise NAD+ comparably, but ex vivo microbiota analysis revealed both are converted to nicotinic acid by gut bacteria — the actual effective NAD+ booster working via Preiss-Handler. Nicotinamide does NOT reach this conversion pathway as efficiently. This collapses the "NMN is closer to NAD+" and "NR bypasses NAMPT" marketing claims: in humans, gut microbiota dominate precursor selection, and individual variation in microbial composition predicts response. Supplement differentiation is largely manufactured.
2024 Hazen/Ferrell paradigm update (Nat Med, PMID 38374343): Niacin's terminal methylation metabolite 4PY (N1-methyl-4-pyridone-3-carboxamide) is causal for endothelial VCAM-1 induction in mice and predicts 3-year MACE in three independent cohorts (adjusted HR 1.89-1.99). The rs10496731 variant is linked to both 2PY/4PY levels and sVCAM-1 in 106,000-subject GWAS meta-analysis. This retrospectively explains HPS2-THRIVE and AIM-HIGH: niacin's lipid benefit is real but its terminal metabolite independently drives atherosclerosis. Any remaining high-dose niacin use for lipids carries this mechanism as a ceiling on benefit.
GPR109A (HCA2) receptor — activated by niacin (not nicotinamide) on adipocytes, Langerhans cells, and colonic macrophages. Drives flushing (phospholipase A2 → PGD2 → DP1/EP2/EP4 vasodilation; TRPV1 also contributes — PMID 39322100). Same receptor drives anti-inflammatory effects in IBD (Singh 2014 Immunity), but butyrate is the endogenous ligand, not dietary niacin.
Sirtuins (SIRT1-7) — NAD+-dependent deacetylases. SIRT1 regulates PGC-1α (mitochondrial biogenesis), FOXO (stress resistance), CLOCK/BMAL1 (circadian). Sinclair's hypothesis: NAD+ decline reduces sirtuin activity → supplementation restores it. Human evidence: NAD+ rises consistently; sirtuin activity in tissues harder to measure; clinical outcomes largely null.
PARPs — DNA-damage-responsive NAD+ consumers. Overactivation depletes cellular NAD+. Theoretical longevity target; human outcome data absent.
SARM1 — emerging axon-degeneration checkpoint; NAD+ depletion activates. Translational research PMID 41502156, 40097763. Nicotinamide riboside small-fiber neuropathy trials terminated (NCT03642990, NCT03685253) — mechanism plausible, clinical translation fragile.
Clinical Trials (BioMCP / ClinicalTrials.gov snapshot 2026-04-17)
| NCT ID | Title/Focus | Phase | Status | Conditions | N | Key Dates |
|---|---|---|---|---|---|---|
| NCT00461630 | HPS2-THRIVE (niacin + laropiprant + statin) | Ph3 | Completed | CVD secondary prevention | 25,673 | 2014 — null MACE, excess AEs |
| NCT00120289 | AIM-HIGH (niacin + statin) | Ph3 | Completed | Low HDL CVD | 3,414 | 2011 — stopped for futility |
| NCT02491567 | ONTRAC (nicotinamide NMSC) | Ph3 | Completed | NMSC prevention | 386 | 2015 — positive (NEJM) |
| NCT02355756 | ONTRANS (nicotinamide NMSC in transplant) | Ph3 | Completed | Kidney transplant + NMSC | 158 | 2023 — failed (NEJM) |
| NCT05405868 | NAMinG (nicotinamide glaucoma) | Ph3 | Recruiting | OAG neuroprotection | 496 | Completion 2027 |
| NCT05740722 | NR progressive MS | Ph2 | Recruiting | Progressive MS | 300 | Completion 2027 |
| NCT03568968 | NADPARK (NR in Parkinson's) | Ph3 | Completed | Early PD | 400 | Neutral on MDS-UPDRS |
| NCT05878119 | MIB-626 (NMN drug, Sinclair/Metro Biotech) | Ph2 | Completed Aug 2025 | Healthy 19-40 yo | 124 | Results pending — will reshape NMN evidence |
| NCT04990869 | NR COPD (Norheim) | Ph2 | Completed | COPD airway inflammation | 40 | 2024 positive (Nat Aging) |
| NCT06208527 | NADage (NR frailty) | Ph2 | Recruiting | Frailty ≥75 yo | — | Pivotal if positive |
| NCT05732051 | NR breast cancer cardioprotection | Ph2 | Recruiting | BrCa on anthracyclines | — | — |
| NCT04844528 | Nicotinamide in CLL + NMSC | Ph2 | Recruiting | CLL patients | — | — |
| NCT06971224 | NADream (NR sleep) | Ph2 | Recruiting | Sleep quality | — | — |
| NCT06991712 | NMN vs NR glaucoma head-to-head | Ph2 | Recruiting | OAG | — | — |
Regulatory Status (2026)
- Niacin: Prescription drug (Niacor, Niaspan, multiple ANDAs). Removed from CVD guidelines post-HPS2-THRIVE; restricted to severe hypertriglyceridemia adjunct (AACE 2025 PMID 39919851, ACC/AHA 2018). Most ER formulations discontinued.
- Nicotinamide: GRAS dietary supplement; no FDA/EMA drug approvals; safe to 3 g/day per consensus.
- Nicotinamide Riboside: FDA NDI acknowledged 2018, GRAS 2018; EU Novel Food authorized 2020; Niagen is trademarked to Niagen Bioscience (formerly ChromaDex).
- NMN: FDA excluded from supplement definition Nov 2022 (prior IND by MetroBiotech under FDCA 201(ff)(3)(B)) → reversed 29 Sept 2025 → NDI status formally reinstated 2 Dec 2025 via letters to major ingredient suppliers. NMN is once again a lawful US dietary supplement. Japan: legal food ingredient (large consumer market). China: supply-chain dominant. EU: novel food unauthorized. Australia/NZ: banned since 2022-2024.
Ataraxia Verdict (as of 2026-04-17)
Evidence Classification (Mode 5)
| Claim | Relationship | Bradford Hill | Safety Flag | Key Weakness |
|---|---|---|---|---|
| Pellagra treatment | DC | 9 | -- | Historical evidence, no equipoise for modern RCT |
| NMSC prevention (immunocompetent) | PC | 7 | -- | Single major RCT (ONTRAC); benefit requires continuous use |
| NMSC prevention (transplant) | RC | 3 | -- | ONTRANS 2023 definitively negative |
| NAD+ elevation (NR/NMN) | SE | 8 | -- | Surrogate only — does not predict clinical outcome |
| Insulin sensitivity NMN (prediabetic PM women) | UCC | 3 | -- | Yoshino 2021 N=25 not replicated; 3 meta-analyses null |
| Muscle/sarcopenia NR+NMN ≥60 | RC | 2 | -- | Prokopidis 2025 definitive null |
| Cognition NR in MCI | RC | 2 | -- | Orr 2023 null; pTau-217 biomarker insufficient |
| CVD prevention niacin | RC | 9 (for null) | WARN | Cochrane 2017 + Hazen 2024 4PY mechanism |
| COPD inflammation NR | PC | 4 | -- | Single Ph2, industry-funded |
| PAD walking NR | PC | 3 | -- | Single Ph2, modest effect, needs replication |
| Glaucoma neuroprotection | PC | 4 | -- | Ph2 positive; Ph3 NAMinG pending 2027 |
| Longevity human | ME | 1 | -- | Pure mouse extrapolation; no human outcome data |
| Topical skin (niacinamide) | PC | 6 | -- | Consistent derm evidence; effect size moderate |
Hype Check (Mode 1)
- Appeal to nature: "vitamin = safe" conflates RDA repletion with pharmacological mega-dosing; false for niacin (4PY mechanism), theoretical for long-term high-dose nicotinamide
- Species generalization: "NR/NMN extends lifespan in mice → will extend lifespan in humans" is the dominant unsupported inference across the longevity space
- Cum hoc ergo propter hoc: "NAD+ declines with age AND aging is bad → restoring NAD+ will reverse aging" is correlation not causation (Gallagher 2026 PRISMA confirms insufficient evidence)
- Authority cascade: Sinclair book + podcast appearances + affiliated companies create circular citation that substitutes repetition for replication
- Surrogate-endpoint trap: Virtually every NR/NMN product claim rests on "raises NAD+ by X%" — a surrogate with poor clinical translation record (vitamin E precedent: raised antioxidant markers, did nothing for outcomes)
- Historical cherry-pick: "Coronary Drug Project showed niacin reduced MI" ignores pre-statin era baseline and is overwhelmed by AIM-HIGH, HPS2-THRIVE, Cochrane 2017
Evidence Gaps
- No human outcomes trials for NAD+ IV (Gallagher 2026 PRISMA)
- No Phase-3 MACE-endpoint trial for any NAD+ precursor
- No replication of Ferrell/Hazen 4PY causal mechanism in independent cohorts
- No head-to-head niacin vs nicotinamide vs NR CV-safety RCT
- No sex-stratified hepatotoxicity/flushing niacin trial
- No pregnancy/lactation safety data for NR/NMN
- No data on long-term (>5 yr) NR/NMN safety at biohacker doses
- Zero recent RCTs on niacin for alopecia, bone density, or phosphate-binding in CKD (NOPHOS terminated)
- NADSYN1, SLC22A6, NNMT pharmacogenomic outcome data essentially absent
- Human replication of Slc12a8 NMN transporter remains disputed — Christen 2026 reframes the entire mechanism as gut-microbial
Bias Flags (Mode 4)
- Sinclair commercial conflicts: MetroBiotech (MIB-626 NMN drug), Tally Health, Leap Years — directly affect interpretation of NMN evidence (and 2022 FDA NDI exclusion coincided with MetroBiotech's drug pathway)
- ChromaDex funds a large fraction of NR trial base; Brenner is CSO and vocal NMN critic — interpret Brenner-authored statements comparing NR to NMN accordingly
- Elysium funded COPD trial (Norheim 2024) and separates from ChromaDex ecosystem
- Three null NMN meta-analyses (2024-2025) arrive with author statements that the field "exaggerates benefits" — rare explicit call-out
- Hazen lab has no commercial supplement interest, strengthening 4PY finding's credibility
- ONTRAC positive + ONTRANS negative together show nicotinamide benefit is population-specific — a common bias is to cite ONTRAC without ONTRANS
Manipulation Flags (Mode 2)
- Industry marketing: "Clinically proven to raise NAD+" language on virtually all NR/NMN labels. Label claims trade on surrogate endpoint while implying clinical outcomes. "No-flush niacin" (inositol hexanicotinate) is a persistent market category despite Meyers 2003 showing near-zero biological activity.
- Influencer economics: Sinclair (MetroBiotech, Tally, Leap Years + media saturation across Rogan/Attia/Huberman); Brenner (ChromaDex CSO); Rhonda Patrick (Tru Niagen affiliate); Dave Asprey (NR → NMN affiliate shift); Ben Greenfield, Siim Land (affiliate economies); Charles Brenner's "longevity skeptic" media positioning is itself commercially aligned.
- Counter-narrative manipulation: "Statins suppressed niacin to protect their market" is a conspiracy-adjacent framing used in orthomolecular spaces. HPS2-THRIVE is a real 25,673-patient trial with excess AEs; Cochrane 2017 is an independent meta. The 2024 Hazen mechanism paper further weakens the conspiracy frame.
- Cui bono summary: Positive hype benefits ChromaDex (NR), MetroBiotech/Shinkowa/Mitsubishi (NMN), Niagen Bioscience, Sinclair's companies, affiliate podcasters, Japanese premium NMN retail. Negative hype benefits statin manufacturers marginally (niacin was never meaningful competition post-2014). The asymmetry is heavily tilted toward pro-supplement manipulation, not pharma-fearmongering.
- Supply chain economics: NMN raw material cost ~$2-3/month for 500 mg/day; retail $40-80/month. NR similar markup. Japanese premium NMN $600-1300/bottle reflects consumer price insensitivity, not manufacturing cost.
- Red team highlight (10 angles): The most concerning angle is historical precedent — vitamin E raised antioxidant biomarkers, didn't translate to clinical benefit, and chronic high-dose was eventually associated with mortality signals. NR/NMN reliably raise the surrogate (NAD+); clinical translation at 10+ years of RCTs has produced few durable wins and the Hazen 2024 paper reveals niacin's terminal metabolite is atherogenic. A scenario where 2035 NR/NMN data looks like 2015 vitamin E data is plausible.
Decision Support (Mode 3 — Clarity Compass)
- Health utility score: 5/10 — strong for deficiency states and NMSC secondary prevention (immunocompetent); weak-to-null for the longevity/metabolic claims that drive market hype; definitively negative for the historical cardiovascular indication. Evaluated independently of any current stack or goal set.
- Opportunity cost: Nicotinamide is negligible ($3-8/mo); NR/NMN meaningful ($35-80/mo, tolerance for 2/5 clinical evidence). Niacin for lipids is now an active harm to avoid.
- Verdict: CONDITIONAL
- Nicotinamide 500 mg BID — CONDITIONAL for immunocompetent adults with ≥2 prior NMSC (strong evidence); baseline nicotinamide 250-500 mg/day as a low-cost NAD+-support / anxiolytic / sleep option is a reasonable WATCH-tier choice for motivated users
- NR 300-1000 mg/day — WATCH LIST; biochemistry real, disease-modifying signals sparse; reasonable for highly motivated users ≥50 who accept 2/5 clinical evidence and premium cost; AVOID during training cycles for athletes
- NMN 250-500 mg/day — WATCH LIST; regulatory uncertainty resolved (2025), but three null meta-analyses and the Christen 2026 mechanism paper argue against preferential selection over NR
- Niacin for CVD — SKIP definitively (Cochrane 2017 + Hazen 2024)
- Niacin for severe hypertriglyceridemia — CONDITIONAL only after statin + fibrate failure, under specialist care
- Inositol hexanicotinate "no-flush niacin" — SKIP (does not release meaningful niacin)
- Conditions (if conditional): NMSC history (≥2 prior), documented pellagra/deficiency, INH therapy in malnourished patient, severe hypertriglyceridemia unresponsive to standard care, or emerging evidence-based indication (glaucoma pending NAMinG 2027).
Bottom Line
Vitamin B3 is four compounds with four evidence profiles. The strongest real-world utility is deficiency repletion (pellagra, alcoholism, INH) and nicotinamide for NMSC secondary prevention in immunocompetent adults. The longevity industry's flagship promise — NR and NMN reversing aging — remains at the "raises a surrogate" stage after a decade of trials, with three 2024-2025 meta-analyses explicitly null on the metabolic and muscle endpoints that most users care about. The 2024 Hazen/Ferrell paper is the most important B3 development of the decade: niacin's 4PY metabolite is mechanistically atherogenic, consolidating the case that the historical CV indication was not just null but actively harmful. The 2026 Christen paper consolidates the case that NR and NMN are biochemically interchangeable via gut microbiota, collapsing most product-differentiation marketing. Use nicotinamide for pellagra, NMSC prevention, and general NAD+ support. Avoid niacin for lipids. Treat NR/NMN as an expensive optimism trade with real biochemistry and thin clinical outcomes.
Practical Notes
Brands & Product Selection
Nicotinamide: Now Foods 500 mg (cheap, reliable); Thorne (premium, COA-transparent); Life Extension; Source Naturals. Avoid anything labeled "niacin" if you want nicotinamide — conflation is pervasive.
Niacin: Nature's Bounty / Now IR 500 mg (generic, OK); Life Extension (premium IR). AVOID: any SR (slow-release) niacin, including Slo-Niacin. Niaspan Rx ER is available but guideline-abandoned and expensive. Inositol hexanicotinate from Solgar / Cardiovascular Research / Now: marketing-only — does not meaningfully release niacin per Meyers 2003.
NR: Tru Niagen (Niagen Bioscience, market leader, assay-verified); Thorne Niacel 400; Life Extension NAD+ Cell Regenerator; Elysium Basis (NR + pterostilbene, premium); ProHealth Longevity NR. Off-brand NR (Jarrow, Swanson) has variable assay — ChromaDex 2024 industry survey found 87% of non-branded NR products missed label (conflicted source, treat directionally).
NMN: Renue By Science (liposomal/sublingual, transparent COAs); ProHealth Longevity Uthever (clinically-studied raw material); DoNotAge (EU-favored, good $/mg); Jinfiniti Vitality Boost; Alive By Science; NOVOS Core (combined longevity formula, Sinclair-adjacent messaging). Japan-exclusive premium: Shinkowa NMN PURE series (99.8% purity, cult-status but $600-1300/bottle). Avoid no-name Amazon NMN below $0.10/mg — quality assay is unreliable.
Topical niacinamide: The Ordinary Niacinamide 10% + Zinc 1% ($7, value pick); Paula's Choice 10% Booster; Anua 10 + TXA 4 (K-beauty, hyperpigmentation); CeraVe / La Roche-Posay drugstore formulations (paired with barrier agents).
Storage & Handling
- Nicotinamide, niacin: stable at room temp, 2-year shelf life; keep dry
- NR: moisture-sensitive; refrigerate after opening to preserve stability
- NMN: moisture and light-sensitive; refrigerate after opening; some retailers ship with ice packs
- Topical niacinamide: degrades to niacin (flushing-capable) in aqueous formulations if pH drifts — buy brands with pH control and opaque packaging
Palatability & Compliance
- Niacinamide: tasteless, easily taken with any meal
- NR: capsules preferred; powder is bitter
- NMN: sublingual is premium community choice; powder is neutral to slightly sweet
- Niacin IR: flushing compliance is the #1 reason for discontinuation — expect 1-2 weeks of flushing before tachyphylaxis develops
Exercise & Circadian Timing
- All NAD+ precursors: morning dosing is community rule; evening dosing causes insomnia in a common minority
- NR specifically: the Dollerup 2020 Sci Adv rat paper suggests NR may blunt training-induced mitochondrial adaptations in high-volume training — conservative recommendation is to skip NR during peak training cycles for athletes
- Niacin: take with the largest meal of the day to slow absorption and reduce flushing peak
- Aspirin 325 mg 30 minutes before niacin dose reduces flushing intensity via COX blockade
Reference Ranges (Expected Biomarker Changes)
| Biomarker | Baseline Range | Expected Change | Timeline |
|---|---|---|---|
| Whole-blood NAD+ | 30-70 µM (age-dependent) | +40-150% with NR 300-1000 mg | 2-4 wk |
| Whole-blood NAD+ (NMN) | Same | +11-38% with NMN 250-1250 mg | 2-4 wk |
| Urinary N-methylnicotinamide | >0.8 mg/g creatinine (sufficient) | Rises with supplementation | Days |
| HDL-C (niacin) | — | +20-35% | 4-12 wk |
| Triglycerides (niacin) | — | -20-40% | 4-12 wk |
| Lp(a) (niacin) | — | -20-30% | 4-12 wk |
| HbA1c (niacin) | — | +0.3-0.5% (adverse) | 6-12 wk |
| 2PY / 4PY | Variable | Rise with niacin (atherogenic per Hazen 2024) | Days |
Cost (USD/month)
- Nicotinamide 500 mg BID: $3-8
- Niacin IR 500 mg: $5-12
- NR 300 mg: $35 (Tru Niagen subscription) to $60 (retail)
- NR 1000 mg: $60-90
- NMN 500 mg: $40-80
- NMN 1000 mg: $80-150
- Topical niacinamide 10%: $7-40
- Japanese premium NMN: $300-1300 (status/gift purchasing, not cost-effective)
What We Don't Know
- Whether any NAD+ precursor extends healthspan or lifespan in humans (Gallagher 2026 PRISMA)
- Whether Ferrell/Hazen 4PY atherogenesis replicates in independent cohorts and whether it applies to dietary (RDA) niacin vs pharmacologic doses only
- Whether NMSC prevention extends to primary prevention in unaffected adults
- Whether NAMinG Ph3 glaucoma trial (2027 readout) validates the Hui/De Moraes Ph2 signal
- Whether MIB-626 Ph2 (Sinclair/Metro Biotech, results pending) changes NMN's clinical profile
- Whether long-term (>5 yr) high-dose NR/NMN has late-emerging oncologic or metabolic signals
- Whether gut microbiota composition (Christen 2026) predicts individual NR/NMN response enough to be clinically actionable
- Whether Slc12a8 direct NMN transport exists in humans (mouse-dominant evidence, human dispute)
- Whether the rat training-adaptation-blunting signal (Dollerup 2020) applies to human athletes
- Whether pellagra case definitions need updating for subclinical presentations in modern high-income populations
- Whether trigonelline (coffee, fenugreek) supplementation supports NAD+ status as suggested by Membrez 2024
References
Meta-analyses & Systematic Reviews
- Schandelmaier 2017 Cochrane PMID 28616955 — 23 RCTs/N=39,195 niacin no CV benefit (definitive)
- Prokopidis 2025 J Cachexia Sarcopenia Muscle PMID 40275690 — NR+NMN null for sarcopenia ≥60
- Chen 2024 Curr Diab Rep PMID 39531138 — NMN null for glucose/lipid (8 RCTs)
- Zhang 2025 Crit Rev Food Sci Nutr PMID 39116016 — NMN null; authors: "exaggeration of benefits may exist"
- Oliveira-Cruz 2024 Horm Metab Res PMID 39111741 — NAD+ precursors metabolic syndrome null
- Zhang 2026 Nutrients PMID 41901064 — NMN DBP -2.15 mmHg (modest, ≥60 subgroup)
- Gallagher 2026 Ageing Res Rev PMID 41655607 — PRISMA 113 studies: NAD+ anti-aging inconclusive
- Mainville 2022 J Cutan Med Surg PMID 35134311 — nicotinamide NMSC meta
- Rad 2024 Eur J Nutr PMID 38761279 — niacin inflammation modest
Landmark RCTs
- Chen 2015 NEJM PMID 26488693 — ONTRAC: nicotinamide 500 mg BID -23% NMSC (positive)
- Allen 2023 NEJM PMID 36856616 — ONTRANS: nicotinamide failed in kidney transplant (negative)
- HPS2-THRIVE 2014 NEJM PMID 25014686 — N=25,673, niacin no CV benefit, excess AEs
- AIM-HIGH 2011 NEJM PMID 22085343 — N=3,414, niacin no benefit, stopped for futility
- Yoshino 2021 Science PMID 33888596 — NMN 250 mg improved muscle insulin signaling, prediabetic PM women
- Martens 2018 Nat Commun PMID 29599478 — NR 1000 mg raised NAD+ 60% healthy adults
- Dellinger 2017 PMID 29184669 — NR dose-response human
- Orr 2023 Geroscience PMID 36859743 — NR null for MCI cognition
- Dollerup 2018 AJCN PMID 29992272 — NR null for insulin sensitivity in obese men
- Norheim 2024 Nat Aging PMID 39548320 — NR positive for COPD airway IL-8
- McDermott 2024 Nat Commun PMID 38871717 — NICE: NR modestly positive for PAD 6-min walk
- Wu 2025 Alzheimers Dement PMID 39817194 — NR lowered pTau-217 in MCI (biomarker signal)
- Wu 2025 EClinicalMedicine PMID 41357333 — NR null for long-COVID cognition/fatigue
- Shoji 2025 Aging Cell PMID 40459998 — NR positive for Werner syndrome
- Lin 2025 Geroscience PMID 40770531 — NR+Ex null for HTN
- Morifuji 2024 Geroscience PMID 38789831 — NMN positive for older-adult walking/sleep (Japan)
- Hwang 2025 Arch Dermatol Res PMID 40498148 — nicotinamide SOTR cohort NMSC (extends ONTRAC to immunosuppressed)
- Hui 2020 PMID 32721104 & De Moraes 2022 JAMA Ophthalmol PMID 34792559 — nicotinamide Ph2 glaucoma positive
- Pencina 2023 JCEM PMID 36740954 — MIB-626 (NMN) raised NAD+ but no functional change
Mechanism
- Ferrell/Hazen 2024 Nat Med PMID 38374343 — 4PY niacin metabolite causally drives endothelial VCAM-1 and predicts MACE
- Christen 2026 Nat Metab PMID 41540253 — NR and NMN both require gut-microbial conversion to nicotinic acid for NAD+ elevation; collapses product differentiation
- Singh 2014 Immunity PMID 24412617 — GPR109A activation suppresses colonic inflammation (IBD mechanism)
- Cantó 2015 Cell Metab PMID 26118927 — NAD+ metabolism energy homeostasis review
- Verdin 2015 Science PMID 26785480 — NAD+ in aging
- Bieganowski & Brenner 2004 Cell PMID 15137942 — NR kinase discovery
- Lautrup 2019 Cell Metab PMID 31577934 — NAD+ in brain aging
- Migaud 2024 Nat Rev Mol Cell Biol (W4400772772) — gold-standard mechanism review
- Javaid 2024 Arch Biochem Biophys PMID 39322100 — niacin flushing mechanism (GPR109A + TRPV1)
- Membrez 2024 Nat Metab (W4392956639) — trigonelline as novel NAD+ precursor
Safety & Regulatory
- McKenney 1994 JAMA PMID 8309029 — SR vs IR niacin: SR higher hepatotoxicity
- Nawaz 2024 PMID 38193433 — fatal cholestatic DILI from self-dosed ER niacin (single case)
- Camillo 2025 Medicina PMID 40005371 — skin health mechanism; 3 g/day nicotinamide safe long-term
- Tan/Williams 2026 Am J Clin Dermatol PMID 41505062 — "Jury Was Out and Still is" NMSC reappraisal
- Conze 2016 Hum Exp Toxicol PMID 26823174 — NR safety/GRAS
Guidelines
- AACE 2025 PMID 39919851 — dyslipidemia, niacin de-emphasized
- ACC/AHA 2018 PMID 30586775 — niacin severe hypertriglyceridemia adjunct only
- ESPEN 2022 PMID 35365361 — micronutrient guideline
- Stratigos 2020 PMID 32113941 — European SCC guideline
- Hołubiec 2021 PMID 34882669 — pellagra clinical review
- Nabity 2022 Lancet Glob Health PMID 35427527 — INH pellagra Malawi context
- Hegyi 2004 Int J Dermatol PMID 14693013 — pellagra clinical review
Key External References
- NIH Office of Dietary Supplements — Niacin Fact Sheet for Health Professionals
- BioMCP FAERS aggregate data (2026-04-17 snapshot)
- ClinicalTrials.gov via BioMCP
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