Vitamin B3 (Niacin)
Supplements · Vitamins · Supplement, Typed Supps
One form of it causes a harmless but genuinely startling skin flush.
Stage by stage
- Intake (Tablet (nicotinic acid or niacinamide)): Absorbed efficiently in the small intestine.
- Small intestine (Efficient absorption): Form (nicotinic acid vs niacinamide) affects downstream studied effects, not absorption itself.
- Bloodstream (Carried to tissues): Carried in blood throughout the body.
- Energy & cholesterol pathways (Studied at higher doses): Used in energy metabolism; nicotinic acid specifically studied for cholesterol effects at doses well above dietary intake.
What the evidence supports
- Treating and preventing pellagra — strong evidence. Settled. Deficiency causes a distinctive and once-common disease that niacin reverses.
- Lowering triglycerides and raising HDL cholesterol — strong evidence. The biochemical effect is large and reliable at pharmacological doses — which is why it was prescribed for decades.
- Reducing heart attacks and strokes by improving those numbers — insufficient evidence. The instructive one. Two large trials added niacin to statin therapy, moved the lipid numbers as expected, and found no reduction in events — one found more side effects and serious harms. A textbook case of a surrogate marker not delivering.
Typical dose
Nutritional doses are a few tens of milligrams; multivitamins usually supply somewhere around 20 to 35 mg. The lipid-lowering doses that made niacin famous are far higher — 1,500 to 2,000 mg daily in the extended-release trials that defined its modern use, with older immediate-release regimens sometimes going higher still. That is a drug dose, and it belongs with a prescription and monitoring.
Upper limit: 35 mg daily for adults from supplements and fortified foods. That ceiling is about flushing rather than serious harm — the hepatotoxicity and glucose effects appear at the gram-level doses.
Timing
With food to reduce flushing with the nicotinic acid form.
Time to effect
- Weeks: Any reported cholesterol-related effect at higher, medically supervised doses.
Medication interactions
- Statins: The combination raises the risk of muscle damage, and the trials found no added benefit to offset it. (high)
- Diabetes medication: High-dose niacin raises blood glucose and can worsen control. (high)
- Blood pressure medication: Flushing causes vasodilation, which can add to the drop in blood pressure. (moderate)
Common myth
“The flushing means something is wrong.” In reality: The nicotinic acid form causes a harmless temporary flush from blood vessels widening — niacinamide doesn’t cause this but lacks the same cholesterol research.
Food sources
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