What is vitamin B3, and what is its active form in the body?
Vitamin B3 (niacin) refers to two main molecules—nicotinic acid and nicotinamide (niacinamide)—both of which are converted into NAD⁺ (nicotinamide adenine dinucleotide) and NADP⁺ within cells. It is these coenzymes that really do the work: they transport electrons in energy-producing reactions and participate in more than 400 enzymatic reactions in the body. Vitamin B3 is unique among vitamins because the body can also synthesize it from tryptophan (an amino acid)—but this conversion is inefficient (60 mg of tryptophan → 1 mg of niacin). For niacinamide in cosmetics, see the dedicated page on niacinamide. The full range of B vitamins is available in the store.
- NAD⁺: The Central Energy Cofactor: NAD⁺ is essential for glycolysis (glucose breakdown), the Krebs cycle, and the mitochondrial respiratory chain—without NAD⁺, cells can no longer produce ATP efficiently—NAD⁺ is also the substrate for sirtuins (SIRT1–SIRT7) — longevity enzymes that regulate DNA repair, inflammation, and metabolism — its levels decline with age, which has fueled growing interest in supplementation with NAD⁺ precursors (NMN, NR)
- NADP⁺ and Antioxidant Defense: NADP⁺ is a cofactor for glutathione reductase (which regenerates reduced glutathione—the cellular “master antioxidant”) and G6PD (pentose phosphate pathway—NADPH production) — Vitamin B3 therefore indirectly contributes to cellular protection against oxidative stress
- DNA repair: NAD⁺ is the substrate for PARPs (poly-ADP-ribose polymerases)—enzymes that repair DNA breaks following exposure to UV radiation or mutagenic agents—a B3 deficiency impairs this repair → increased risk of mutations
- RDA and niacin equivalents: Adult RDA: 16 mg of niacin equivalents (NE)/day for men, 14 mg for women — 1 NE = 1 mg of niacin = 60 mg of dietary tryptophan — pregnant women: 18 mg NE/day
- Difference between the two forms: nicotinic acid (niacin) — effective for cholesterol, causes flushing, not used in cosmetics — nicotinamide/niacinamide — no flushing, used in cosmetics and as a standard supplement, does not lower cholesterol at typical doses
Pellagra and vitamin B3 deficiency: a forgotten disease making a comeback?
- Pellagra—the “4 Ds” disease: Dermatitis (symmetrical, photosensitive skin lesions)—Diarrhea—Dementia (confusion, hallucinations) — Death (if left untreated) — historically linked to a diet based on non-nixtamalized corn (native corn contains non-absorbable bound niacin) — still present in disadvantaged populations and among chronic alcoholics in developed countries
- Who is at risk of B3 deficiency today?: chronic alcoholics (alcohol blocks niacin absorption and disrupts tryptophan conversion) — malnourished individuals or those on very restrictive diets — carcinoid syndrome (a tumor that consumes large amounts of tryptophan to produce serotonin → less available for niacin) — Hartnup disease (a genetic disorder affecting tryptophan absorption) — people taking isoniazid (an anti-tuberculosis drug that blocks the conversion of tryptophan to niacin)
- Subclinical signs of a deficiency: persistent fatigue and lack of energy — irritability and difficulty concentrating — digestive problems (nausea, mild diarrhea) — sun-sensitive skin that “peels” abnormally — these signs disappear quickly with a diet rich in B3 or modest supplementation
- Good dietary sources: red meat and poultry (4–8 mg/100 g) — tuna and salmon (8–14 mg/100 g — fish are among the best sources) — liver (10–16 mg/100 g) — peanuts (14 mg/100 g) — fortified whole grains — mushrooms (4 mg/100 g) — coffee (a significant source due to the niacin released during roasting)
Niacin and Cholesterol: A Complicated Relationship
- Niacin (nicotinic acid) is the most potent natural agent affecting HDL: at pharmacological doses (1 to 3 g/day), niacin increases HDL (good cholesterol) by 15 to 35% — reduces triglycerides by 20 to 50% — reduces LDL by 5 to 25% — mechanism: inhibits lipolysis in adipose tissue → fewer free fatty acids reach the liver → reduced production of VLDL and LDL — these doses apply only to nicotinic acid (niacin), not niacinamide — only under medical supervision
- The niacin “flush ”: at dosesof 100 mg or higher, nicotinic acid causes flushing (redness, warmth, and itching of the face and trunk) — mechanism: release of prostaglandin D2 by skin mast cells — lasts 20 to 60 minutes — benign but uncomfortable — alleviated by: taking it with a meal + aspirin 30 minutes beforehand + extended-release forms — niacinamide does not cause this reaction
- Extended-release (ER) formulations: reduce flushing but increase the risk of hepatotoxicity (caution is advised with generic extended-release formulations not taken under medical supervision) — immediate-release formulations have the best hepatic safety profile — extended-release formulations taken under medical supervision (Niaspan) are validated
- Recent clinical studies: large trials (AIM-HIGH, HPS2-THRIVE) have not shown any additional cardiovascular benefit from adding niacin to statins in patients whose condition is already well-controlled — niacin remains an option for patients with very low HDL who are intolerant to statins, under strict cardiological supervision— omega-3s remain the natural standard of care for high triglycerides
- Important drug interactions: statins + high-dose niacin → risk of myopathy or rhabdomyolysis — antidiabetic medications → niacin may increase fasting blood glucose (insulin resistance) — alcohol → exacerbates flushing and increases the risk of liver damage — always inform your doctor of any niacin supplementation
How to use vitamin B3 effectively based on your goals?
- For energy and fatigue: 50–100 mg/day of niacinamide in a B-complex formula — synergistic with B12,folic acid, and magnesium for energy coenzymes — B-vitamin formulas available at pharmacies
- For the skin (oral use): 500 mg to 1 g of niacinamide per day — reduces sebum secretion — systemic anti-inflammatory effect on the skin — prevention of skin cancers (meta-analysis showing a reduction in actinic keratoses and basal cell carcinomas in at-risk individuals with 500 mg × 2/day) — different from topical use — the niacinamide page details cosmetic applications
- For cholesterol (only under medical supervision): nicotinic acid 1 to 3 g/day — indicated only if HDL is very low or in cases of severe hypertriglyceridemia resistant to other treatments — never self-prescribe at these doses — regular liver function tests are mandatory — see the hypercholesterolemia page
- Precautions regarding overdose: niacinamide > 3 g/day → nausea + possible hepatotoxicity — nicotinic acid > 3 g/day → hepatotoxicity + hyperuricemia (risk of a gout attack) + insulin resistance—the EFSA sets the limit for niacinamide at 900 mg/day without medical supervision
