Niacin (Nicotinic Acid / Vitamin B3) — Supplements
NAD+ precursor via Preiss-Handler pathway; the only supplement proven to raise HDL by 15-35% and reduce Lp(a) by 20-30%; flush-based mechanism is pharmacologically distinct from niacinamide.
Overview
Niacin (nicotinic acid, vitamin B3) is a water-soluble B vitamin and the direct precursor to NAD+ via the Preiss-Handler pathway — making it distinct from niacinamide (nicotinamide, which enters NAD+ synthesis via salvage) and from the newer NAD+ precursors NMN and NR. At pharmacological doses (500–2,000 mg/day), niacin is one of the oldest and most effective lipid-modifying agents, capable of raising HDL cholesterol by 15–35%, reducing triglycerides by 20–50%, reducing LDL by 15–25%, and uniquely reducing Lp(a) by 20–30% — the only non-PCSK9-inhibitor agent with meaningful Lp(a)-lowering capability. The AIM-HIGH and HPS2-THRIVE trials failed to show cardiovascular mortality benefit of extended-release niacin added to statins in modern cohorts, shifting its clinical role; however, in patients with isolated hypo-HDL or elevated Lp(a) without statin intolerance, niacin retains evidence-based utility. At lower nutritional and longevity doses (100–500 mg/day), niacin is used as an NAD+ precursor — it does not cause flushing below ~100 mg and provides robust NAD+ replenishment through all three major biosynthetic pathways. The characteristic niacin flush (prostaglandin D2-mediated cutaneous vasodilation) is pharmacological, not toxic — it can be attenuated by aspirin 325 mg taken 30 minutes before dosing, gradual dose titration, or by using extended-release formulations.
Indications
- NAD+ precursor for longevity and cellular energy at nutritional doses (100–500 mg)
- Dyslipidemia — hypo-HDL, hypertriglyceridemia, elevated Lp(a) at pharmacological doses (500–2,000 mg)
- Pellagra (niacin deficiency disease) prevention and treatment
- Skin health — niacin deficiency causes dermatitis; pharmacological doses support barrier function
Mechanism of Action
Nicotinic acid enters NAD+ synthesis via the Preiss-Handler pathway: niacin → nicotinate mononucleotide (NaMN, via NAPRT) → nicotinate adenine dinucleotide (NaAD) → NAD+ (via NADS). This pathway is active in tissues with high NAPRT expression (liver, kidney, heart) and provides a route to NAD+ distinct from NMN/NR (Salvage pathway) or de novo tryptophan synthesis
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| Niacin (immediate-release, nutritional/NAD+ dose) | 100–500 mg | Once daily with food | Below flush threshold for most people; effective NAD+ precursor range; start at 100 mg/day and titrate |
| Niacin (immediate-release, lipid-modifying dose) | 500–2,000 mg | Once to twice daily with food | Take aspirin 325 mg 30 min before to reduce flush; titrate slowly from 250 mg/day over 4-6 weeks; requires LFT monitoring |
| Niacin (extended-release, Niaspan-equivalent) | 500–2,000 mg | Once daily at bedtime | Reduced flushing compared to IR; higher hepatotoxicity risk than IR at same dose; monitor LFTs every 3-6 months |
Safety & Contraindications
- Niacin flush: prostaglandin D2-mediated flushing, warmth, tingling, itching — harmless but discomforting; occurs at doses >100 mg of immediate-release niacin; mitigated by aspirin, food, gradual titration, or extended-release formulations
- Hepatotoxicity: extended-release niacin (Niaspan) at doses >1,500 mg/day carries significant hepatotoxicity risk; immediate-release niacin at therapeutic doses can elevate liver enzymes; monitor LFTs at pharmacological doses
- Hyperglycemia: niacin impairs insulin sensitivity at pharmacological doses — monitor fasting glucose in at-risk patients; less concern at longevity doses <500 mg
- Hyperuricemia: niacin competes with uric acid for tubular secretion — can precipitate gout in susceptible individuals at pharmacological doses
- Do NOT confuse with niacinamide (nicotinamide) — niacinamide does not cause flushing but also does not provide the lipid-modifying or Lp(a)-lowering benefits of nicotinic acid
- Drug interactions: niacin enhances hepatotoxicity risk when combined with statins; potentiates antihypertensive effects; interacts with anticoagulants