Vitamin B3 (Niacin)
water-soluble
Key Takeaways
- Precursor to NAD+ and NADP+, coenzymes in 400+ enzymatic reactions for energy metabolism, DNA repair, and cell signaling
- FDA daily value is 16 mg NE (niacin equivalents)
- Deficiency causes pellagra: dermatitis, diarrhea, dementia, and death if untreated
- Available as nicotinic acid (causes flushing) and nicotinamide (no flushing)
- Note: No PubMed studies in research data; content based on established biochemistry and FDA daily value
Evidence Spectrum
0 studies reviewed →Pellagra prevention and treatment
Niacin deficiency causes pellagra, historically devastating in corn-dependent populations. Food fortification eliminated it in developed countries. Established biochemistry; no PubMed citations in research data.
Cellular energy metabolism
As precursor to NAD+ and NADP+, niacin is essential for 400+ enzymatic reactions. Fundamental biochemistry; no PubMed citations in research data.
16 mg NE
RDA (Adults (FDA Daily Value))
35 mg
Upper Limit
water-soluble
Solubility
Role in the Body
Vitamin B3 (niacin) encompasses nicotinic acid and nicotinamide, both precursors to NAD+ and NADP+. These coenzymes participate in 400+ enzymatic reactions for energy metabolism (glycolysis, TCA cycle, oxidative phosphorylation). NAD+ also serves as substrate for PARPs (DNA repair) and sirtuins (stress response/longevity signaling). The body synthesizes niacin from tryptophan (60 mg tryptophan = ~1 mg NE). No PubMed studies were available in the research data.
- Precursor to NAD+ and NADP+ coenzymes
- Cellular energy metabolism (glycolysis, TCA cycle, oxidative phosphorylation)
- DNA repair via PARP enzymes
- Cell signaling and stress response via sirtuins
- Tryptophan-to-niacin conversion pathway
Supplement Forms
Nicotinic acid (niacin)
RecommendedBioavailability: 0.7%
Causes vasodilatory flushing above 35 mg. Prescription doses (1-3 g) for dyslipidemia.
Nicotinamide (niacinamide)
RecommendedBioavailability: 0.7%
No flushing. Most common OTC supplement form.
Nicotinamide riboside (NR)
Bioavailability: %
NAD+ precursor marketed for anti-aging. No studies in research data to evaluate.
Food Sources
Poultry (chicken, turkey)
Fish (tuna, salmon)
Beef and pork
Fortified cereals and bread
Peanuts and peanut butter
Mushrooms
Green peas
Deficiency
Prevalence: Pellagra rare in developed countries due to fortification. Concern in corn-dependent diets and alcoholism.
Symptoms:
- Dermatitis (photosensitive, bilateral, symmetrical)
- Diarrhea
- Dementia (neuropsychiatric symptoms)
- Death if untreated (the 4 Ds of pellagra)
Risk Factors:
- Corn/maize-dependent diets without nixtamalization
- Chronic alcoholism
- Carcinoid syndrome (tryptophan diverted to serotonin)
- Hartnup disease
- Isoniazid therapy
Safety & Interactions
Possible Side Effects:
- • Vasodilatory flushing with nicotinic acid above 35 mg (not with nicotinamide)
- • Hepatotoxicity at pharmacological doses (1-3 g/day), especially sustained-release
- • GI upset at high doses
Drug Interactions:
- • Statins: increased myopathy risk with high-dose niacin
- • Isoniazid: depletes niacin, may precipitate pellagra
- • Alcohol: increases niacin requirements
Contraindications:
- • Active liver disease
- • Active peptic ulcer disease
- • Severe hypotension
Frequently Asked Questions
Niacin vs niacinamide?
Both produce NAD+. Niacin (nicotinic acid) causes flushing; niacinamide does not. Niacinamide is the common supplement form.
What causes niacin flushing?
Nicotinic acid triggers prostaglandin-mediated vasodilation above 35 mg. Not harmful but uncomfortable.
Can I get enough from food?
Yes. Poultry, fish, beef, fortified cereals, and peanuts are rich sources. FDA DV of 16 mg NE is easily achievable.
Research Sources
14 peer-reviewed studies analyzed from PubMed. 0 directly cited in this review.