Vitamin B3
Niacin/Niacinamide (Vitamin B3)
Vitamin B3 exists in two primary forms: niacin (nicotinic acid) and niacinamide (nicotinamide), both of which serve as precursors to NAD+ and NADP+, coenzymes essential for hundreds of metabolic reactions. Niacin is widely used at pharmacological doses to improve lipid profiles by raising HDL cholesterol and lowering triglycerides, while niacinamide is favored for skin health, anti-inflammatory effects, and NAD+ replenishment without causing the characteristic flushing. Both forms are used to address B3 deficiency (pellagra) and are increasingly researched for longevity, metabolic support, and neuroprotection.
Mechanism of Action
Niacin and niacinamide are converted intracellularly to NAD+ (nicotinamide adenine dinucleotide) and NADP+, which are critical coenzymes in glycolysis, the citric acid cycle, oxidative phosphorylation, and DNA repair via PARP enzymes. Niacin additionally acts as an agonist at the GPR109A receptor on adipocytes and immune cells, which mediates the vasodilatory flushing response and contributes to its lipid-modifying effects by suppressing hepatic VLDL secretion and reducing free fatty acid mobilization. Niacinamide does not activate GPR109A, making it flush-free, and it supports NAD+-dependent sirtuins (SIRT1-7) involved in gene regulation, cellular stress response, and aging pathways.
Evidence by Health Goal(18 goals)
Dosing Protocols
With meals to reduce gastrointestinal upset
Appropriate for general B3 sufficiency, NAD+ support, and niacinamide-based supplementation. For niacin-based lipid management, doses of 500-2000mg daily are used under medical supervision with gradual titration to reduce flushing. Immediate-release niacin causes flushing; extended-release formulations reduce this but may increase hepatotoxicity risk at high doses.
Applied to cleansed skin; morning and/or evening
Niacinamide is the form used topically. Common in skincare formulations for reducing hyperpigmentation, minimizing pore appearance, improving skin barrier function, and reducing acne-related inflammation. Not used as niacin topically.
Safety & Side Effects
At dietary and low supplemental doses (up to 500mg/day), both niacin and niacinamide are well-tolerated and considered safe for most adults; however, pharmacological doses of niacin (500-2000mg/day) used for dyslipidemia carry meaningful risks including hepatotoxicity, glucose dysregulation, and gout, and should only be used under medical supervision. High-dose niacinamide (>3g/day) has also been associated with liver stress and nausea, and the AIM-HIGH and HPS2-THRIVE trials raised questions about cardiovascular benefit of high-dose niacin when added to statin therapy.
Possible Side Effects
- !Cutaneous flushing (warmth, redness, tingling) - primarily with immediate-release niacin, dose-dependent
- !Gastrointestinal discomfort including nausea, vomiting, or diarrhea at higher doses
- !Pruritus (itching) often accompanying the flushing response
- !Hepatotoxicity risk with high-dose or sustained-release niacin formulations (>1g/day)
- !Dose-dependent elevations in fasting blood glucose, particularly relevant in diabetic patients
- !Hyperuricemia and potential gout exacerbation at pharmacological doses
- !Blurred vision or macular edema (rare, reversible, associated with high-dose niacin)
Interactions
- -High-dose niacin can potentiate the effects of statins, increasing the risk of myopathy and rhabdomyolysis
- -Concurrent use with antihypertensive medications may enhance blood pressure-lowering effects due to vasodilation from flushing
- -May impair glycemic control in patients on insulin or oral hypoglycemic agents by raising fasting blood glucose
- -Aspirin (325mg) taken 30 minutes before niacin reduces prostaglandin-mediated flushing but adds antiplatelet considerations
- -Alcohol consumption can intensify flushing and may increase hepatotoxicity risk when combined with high-dose niacin
Cost & Where to Buy
Generic niacin and niacinamide supplements are widely available and inexpensive at standard doses. Costs increase for branded formulations, flush-free inositol hexanicotinate products, or high-potency NAD+ precursor products. Prescription extended-release niacin (Niaspan) is significantly more expensive and largely discontinued in many markets.
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