Vitamin B3: niacin or nicotinamide, which form and what dose?

Vitamin B3 brings together two molecules that look alike on a label but not inside the body: niacin (nicotinic acid) and nicotinamide. Both are used to make NAD+, the coenzyme that keeps the mitochondria running. At high doses, niacin causes flushing and did not reduce heart attacks in the large trials. Nicotinamide reduced skin cancers in high-risk patients. For an adult eating 2,000 kcal a day, France’s food safety agency (Anses) targets 13.4 mg, an intake that an ordinary diet covers without any supplement.

Vitamin B3: definition, forms and daily requirements

The name covers a family of compounds that the body can all convert into NAD+. It is also known as vitamin PP, for “pellagra preventive”. A deficiency causes pellagra: dermatitis made worse by sunlight, diarrhea, mental disturbances, then death without treatment (Hegyi et al., 2004). Rare in wealthy countries, it remains a threat during food crises. The World Health Organization devotes a whole guide to preventing it.

Requirements are expressed in niacin equivalents (NE), because the liver makes this vitamin from tryptophan, an amino acid found in proteins. As the NIH Office of Dietary Supplements explains, 60 mg of tryptophan yields about 1 mg of niacin equivalent. Since this vitamin is used to burn nutrients, the requirement rises with the energy consumed. Anses sets, for all adults, an average requirement of 1.3 mg NE per megajoule and a reference intake of 1.6 mg NE per megajoule.

Anses also sets two upper safety limits for adults: 10 mg a day for nicotinic acid, 900 mg a day for nicotinamide. The first is low in order to avoid flushing, the hot redness that appears from 30 mg in some people. The second mainly protects the liver. A 500 mg niacin tablet therefore exceeds its limit fifty times over, while a nicotinamide capsule of the same strength stays below its own.

Mechanism: how vitamin B3 becomes NAD+

Whatever the form swallowed, the vitamin is first used to produce NAD+ (nicotinamide adenine dinucleotide) and its derivative, NADP+. These coenzymes carry electrons in the reactions that extract energy from glucose and fats inside the mitochondria. NAD+ is not simply recycled: three families of enzymes linked to aging consume it.

• PARPs, which repair breaks in DNA and burn NAD+ every time they step in.
• Sirtuins, which adjust gene expression and metabolism to the energy available.
• CD38, an enzyme of immune cells whose activity increases with chronic inflammation.

In human skin, NAD+ declines with age. In 49 people aged 0 to 77, its level fell markedly over the years (r = -0.706 in men), while PARP activity rose in parallel (Massudi et al., 2012). This decline links vitamin B3 to mitochondrial dysfunction, one of the biological hallmarks of aging. Our article on the levers for maintaining your NAD+ places supplements within a broader picture.

The different forms do not all take the same route:

• Nicotinic acid, or niacin, reaches NAD+ through the so-called Preiss-Handler pathway. At high doses, it also activates the GPR109A receptor on immune cells in the skin. These cells then release prostaglandins D2 and E2, which trigger the flush (Benyó et al., 2005).
• Nicotinamide, also called niacinamide, enters the NAD+ recycling pathway directly. It does not activate this receptor: no flushing, but no effect on blood lipids either.
• Inositol hexanicotinate, sold as “no-flush” niacin, releases no measurable nicotinic acid into the blood (Keenan, 2013).
• Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are precursors closer to NAD+, marketed as anti-aging supplements.

What science says about high-dose vitamin B3

The large trials give a clear answer. High-dose niacin improves cholesterol numbers without reducing heart attacks. Nicotinamide shows a targeted effect on the skin. The precursors NR and NMN raise blood NAD+, with no proven clinical benefit. None of these findings calls into question the dietary intake of this vitamin, which remains essential.

Vitamin B3 and cholesterol: better numbers, no fewer heart attacks

Niacin, one of the forms of B3, is the oldest cholesterol drug. The Coronary Drug Project tested it in 8,341 men who had already had a heart attack. It reduced nonfatal recurrences without lowering total mortality during the trial (Coronary Drug Project, 1975). Fifteen years later, mortality was 52.0% in the niacin group versus 58.2% on placebo (Canner et al., 1986).

In the statin era, this benefit was not confirmed. The AIM-HIGH trial added 1,500 to 2,000 mg of extended-release niacin to a statin in 3,414 heart patients. HDL rose from 35 to 42 mg/dL, but cardiovascular events stayed the same: 16.4% versus 16.2%. The trial was stopped for futility (Boden et al., 2011). With 25,673 patients followed for 3.9 years, HPS2-THRIVE confirmed the failure: 13.2% major vascular events versus 13.7% (Landray et al., 2014).

That same trial revealed an excess of serious adverse effects on niacin. Serious disturbances of diabetes control rose by 3.7 percentage points, new cases of diabetes by 1.3 points, infections by 1.4 points and bleeding by 0.7 points. Across 11 trials and 26,340 people, the increase in diabetes risk reaches 34%: one extra case for every 43 people treated for 5 years (Goldie et al., 2016). The Cochrane review of 23 trials and 39,195 participants finds no reduction in mortality or heart attacks, while discontinuations due to adverse effects are multiplied by 2.17 (Schandelmaier et al., 2017). The European Medicines Agency suspended the niacin-laropiprant combination in 2013.

Nicotinamide and skin cancer: a real but targeted effect

The Australian ONTRAC trial tested nicotinamide, the flush-free form of the vitamin, in 386 people who had had at least two nonmelanoma skin cancers in 5 years. They received 500 mg twice a day, or a placebo. After 12 months, the rate of new carcinomas was 23% lower on nicotinamide, and the number of actinic keratoses 13% lower (Chen et al., 2015). Six months after stopping, the effect had disappeared.

In 158 organ transplant recipients on immunosuppressants, the same regimen changed nothing: 207 new skin cancers on nicotinamide versus 210 on placebo (Allen et al., 2023). The ONTRAC dose, 1,000 mg a day, exceeds the 900 mg limit set by Anses. It is a decision to make with a dermatologist, on top of sun protection, the foundation of prevention according to the NHS.

Nicotinamide and glaucoma: signals still to be confirmed

In glaucoma, the nerve cells of the retina run short of energy, and B3 is one of the avenues being explored to restore it. In 57 patients already on treatment, 1.5 g then 3 g of nicotinamide a day improved an electrical measure of retinal function by 14.8%, versus 5.2% on placebo (Hui et al., 2020). A phase 2 trial combining nicotinamide and pyruvate counted 15 improved visual field points, versus 7 on placebo, in 32 patients (De Moraes et al., 2022). These trials lasted a few weeks: longer studies are underway.

NR and NMN: NAD+ goes up, benefits remain to be proven

Nicotinamide riboside, a form of B3 close to NAD+, does raise NAD+ levels in humans (Martens et al., 2018). In 12 older men, 1 g a day for 21 days enriched muscle with NAD+ derivatives, without improving the energy output of the mitochondria (Elhassan et al., 2019). In 40 men with obesity, 2 g a day for 12 weeks did not improve insulin sensitivity (Dollerup et al., 2018).

Recent meta-analyses point the same way. After age 60, NMN and NR improved neither muscle mass, nor grip strength, nor walking speed (Prokopidis et al., 2025). Across 15 NMN trials, short-term tolerance is good. Blood sugar, weight and lipids do not change, and only diastolic blood pressure falls slightly (Yang et al., 2026).

Excess vitamin B3: the 2PY and 4PY metabolite lead

The liver eliminates the surplus as methylated derivatives, including 2PY and 4PY. A Cleveland Clinic study published in 2024 linked these waste products to cardiac risk. In two patient cohorts followed for 3 years (2,331 Americans and 832 Europeans), a high 4PY level multiplied the risk of a major adverse cardiovascular event by 1.89 and 1.99 (Ferrell et al., 2024). In mice, 4PY activates VCAM-1, a marker of blood vessel inflammation. This association does not prove that a B3 supplement damages the arteries. It does argue for sticking to actual needs.

In practice: niacin or nicotinamide, which vitamin B3 to choose?

For the vast majority of adults, food covers these needs and the question of which form to choose never arises. Multivitamins most often use nicotinamide at a nutritional dose. High doses are justified only in specific medical situations, with monitoring. The table compares the forms sold in pharmacies or online.

Extended-release niacin deserves a specific warning. In a 1994 trial, 12 of the 23 patients on the “sustained-release” form developed liver damage as the dose was raised to 3 g a day, while no patient on the immediate-release form was affected (McKenney et al., 1994). Nicotinamide is better tolerated. Yet a review of its safety considers it potentially toxic above 3 g a day in adults and advises against any use without supervision (Knip et al., 2000).

For cholesterol, the effective levers lie elsewhere: diet, physical activity and, if needed, statins. Our article on what your cholesterol reveals about your longevity details the targets to aim for. For the skin, nicotinamide never replaces well-chosen sun protection, nor a dermatologist’s advice.

How much vitamin B3? Everyday advice

For a healthy adult, the right dose is the one on the plate: 13.4 mg of niacin equivalent a day for 2,000 kcal. A 120 g (4.2 oz) serving of chicken breast alone provides 16 mg, not counting the tryptophan in its protein. Frank deficiency is confined to severe alcoholism, malabsorption or undernutrition.

The habits that matter for good B3 status:

• Cover your B3 needs through food, with poultry, fish, peanuts or whole grains every day.
• Read the label of any vitamin B3 supplement: “nicotinic acid” or “niacin” above 10 mg a day exposes you to flushing, “nicotinamide” does not.
• Do not buy high-dose niacin for your cholesterol, since the trials showed no reduction in heart attacks.
• Steer clear of “slow-release” niacin sold over the counter, which is toxic to the liver at high doses.
• Above 900 mg of nicotinamide a day, the dose range of the skin and glaucoma trials, plan for medical follow-up and liver function tests.
• Tell your doctor about any use if you have diabetes, liver disease, gout or an ulcer, or if you take a statin.
• After taking niacin, an isolated flush is unpleasant but short-lived. If it comes with feeling faint, shortness of breath or chest pain, call emergency services (911 in the US, 999 in the UK, 112 in Europe).

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Frequently asked questions about vitamin B3

What is the difference between niacin and nicotinamide?

They are two forms of vitamin B3 that meet the same nutritional needs. Niacin, or nicotinic acid, causes flushing from 30 mg in some people and alters blood lipids at around 1.5 to 2 g a day. Nicotinamide does not cause redness and has no effect on cholesterol. Their safety limits differ: 10 mg a day for nicotinic acid, 900 mg for nicotinamide.

How much vitamin B3 does an adult need per day?

France’s food safety agency (Anses) sets the nutritional reference at 1.6 mg of niacin equivalent per megajoule of energy consumed. That works out to about 13.4 mg a day for 2,000 kcal and 16.1 mg for 2,400 kcal. A varied diet covers this requirement, because poultry, fish and peanuts are rich sources. The 1 to 3 g doses used in trials require a medical prescription.

Why does niacin cause flushing?

Niacin, the form of B3 also called nicotinic acid, activates a receptor named GPR109A on immune cells in the skin. These cells then release prostaglandins that dilate the blood vessels of the face and neck. That is the flush, with redness, warmth and tingling. The phenomenon is unpleasant but short-lived. Nicotinamide does not activate this receptor and does not cause flushing.

Should you take niacin for your cholesterol?

No, not on your own initiative. Niacin raises HDL and lowers triglycerides. Yet the AIM-HIGH and HPS2-THRIVE trials, with more than 29,000 patients in total, showed neither fewer heart attacks nor fewer strokes. Niacin did, on the other hand, increase the risk of diabetes, infections and bleeding. Statins and lifestyle remain the levers whose effectiveness has been demonstrated.

Which foods are richest in vitamin B3?

Beef liver, chicken breast and tuna come out on top: a 100 to 120 g (3.5 to 4.2 oz) serving alone covers an adult’s daily requirement. Salmon, peanuts, brown rice, mushrooms and whole-wheat bread round out the intake. Protein counts too, because the liver converts tryptophan into this vitamin, at a rate of 1 mg per 60 mg of tryptophan.

Does nicotinamide protect against skin cancer?

In people who had already had at least two nonmelanoma skin cancers, 500 mg of nicotinamide (vitamin B3) twice a day reduced new cases by 23% over 12 months. The effect disappeared once treatment stopped and was not found in organ transplant recipients. This dose exceeds the 900 mg limit set by Anses: it should be discussed with a dermatologist and does not replace sun protection.