Niacin (Vitamin B3): Niacin Equivalents, ICMR-NIN Requirement, Pellagra and High-Dose Risks

Niacin is vitamin B3, the name shared by nicotinic acid and nicotinamide, which the body builds into the coenzymes NAD and NADP that cells use to draw energy from food. ICMR-NIN's Nutrient Requirements for Indians 2020 sets the recommended allowance at 14 mg a day for a sedentary man and 11 mg for a sedentary woman, with a tolerable upper limit of 35 mg. The body also makes niacin from the amino acid tryptophan, which is why protein counts. This entry in the vitamins section of the handbook covers niacin equivalents, Indian foods, pellagra and large doses.

What does niacin do in the body?

It carries hydrogen between molecules. The joint FAO and WHO expert consultation explains that the amide form sits inside two coenzymes, nicotinamide adenine dinucleotide (NAD) and its phosphate (NADP). NAD works with the enzymes that oxidise fuels and is also needed for DNA repair. NADP works in building reactions, including the synthesis of fatty acids and steroids. A long shortage shows in the skin, the gut and the brain, as the section on pellagra describes.

The two forms differ as medicines. The consultation notes that nicotinamide lacks the drug action of nicotinic acid, which at high doses lowers blood lipids. As nutrients, both are forms of the vitamin. FSSAI's fortification regulations allow either to be added to fortified atta, maida and rice, as an optional nutrient at 12.5 to 20 mg per kg, or 0.75 to 1.2 mg in the 60 g of atta that makes two chapatis.

What is a niacin equivalent, and why does tryptophan count?

A niacin equivalent is 1 mg of niacin from either route: 1 mg eaten ready-made, or about 60 mg of tryptophan that the body converts. The FAO and WHO consultation treats 60 to 1 as the average and warns that individuals differ substantially. The conversion needs riboflavin and vitamin B6, so a shortage of either can cut the yield; the handbook's entry on riboflavin covers the first of these.

This matters for reading Indian food tables. The Indian Food Composition Tables 2017 state that their niacin values represent preformed niacin only, and give the formula: niacin equivalents equal niacin plus tryptophan divided by 60. The table below applies it to common staples, using the same tables' protein and tryptophan figures. Milk shows the gap best: a glass has almost no niacin but enough tryptophan to make about 1.6 mg.

How much niacin do you need under ICMR-NIN's 2020 values?

A sedentary man needs 14 mg a day and a sedentary woman 11 mg, with estimated average requirements of 12 mg and 9 mg. The expert group started from an average requirement of 5.6 mg per 1,000 kcal, derived from studies of niacin metabolites in urine, and scaled it to each group's energy needs, so the allowance rises to 23 mg for a man and 18 mg for a woman doing heavy work. Pregnancy adds 2 mg and breastfeeding 5 mg.

The same report observes that diet surveys in India put average niacin intake at around 10 mg a day, below the allowance for most adults before tryptophan is counted. The FAO and WHO consultation, which states its figures in niacin equivalents, recommends 16 mg for men and 14 mg for women. ICMR-NIN's brief note shows the allowances for the reference man and woman, 18 and 14 mg, unchanged from the 2010 edition.

Which Indian foods are rich in niacin?

Groundnuts lead the everyday list, followed by chicken, meat and fish, with whole cereals and pulses supplying a steady base. The portions below are calculated from the Indian tables' figures for preformed niacin, with raw weights for grains, pulses and flesh foods. For the ranked list of every food, see the niacin table of Indian foods.

The vegetarian pattern is plain: apart from groundnuts no single vegetarian staple is rich, so intake depends on the total quantity of whole grains and pulses eaten. A 30 g handful of groundnuts gives as much preformed niacin as about 140 g of atta; the comparison of peanuts and almonds has both panels, and masala peanuts is one way to eat them. Milk looks poor here only because its contribution arrives through tryptophan.

Pellagra, maize and jowar: the Indian story

Severe niacin deficiency causes pellagra. The FAO and WHO consultation describes a chronic wasting disease with a red dermatitis that is bilateral and symmetrical, diarrhoea from inflammation of the gut lining, and mental changes that begin with insomnia and apathy and can end in dementia. A 2014 case report from Ludhiana recalls the textbook summary of four Ds, dermatitis, dementia, diarrhoea and death, and notes that the rash usually sits on skin exposed to sunlight.

WHO describes pellagra as classically associated with a diet based on maize that has not been treated with alkali. The Indian tables show part of the reason: maize protein holds 0.57 g of tryptophan per 100 g of protein, against 1.03 g in jowar, 0.99 g in atta and 1.27 g in rice. A person living on maize as the main cereal, with little dal, milk or groundnut beside it, gets little niacin by either route.

India's own chapter concerns jowar. Writing in the Indian Journal of Medical Research in 2013, C. Gopalan recalled that pellagra was endemic up to the 1950s, that people who ate jowar almost exclusively were prone to it, and that research pointed to the millet's high leucine content. The advice given was to vary the cereals, not to hand out nicotinic acid, and pellagra faded once cheap rice and wheat reached ration shops. The Indian tables put leucine at about 12 g per 100 g of protein in jowar and maize, against 8.1 g in rice and 6.1 g in atta.

None of this makes jowar or maize unsafe. The disease belonged to diets built on one cereal and very little else. A bhakri eaten with dal, groundnut chutney, curd and vegetables is a different diet from jowar alone, and the jowar nutrition page shows what the grain supplies. The 2024 Dietary Guidelines add that grains are limited in tryptophan and that pulses supply what they lack.

Who is at risk of niacin deficiency today?

People whose diet rests on a single cereal with very little protein, and people whose illness or drinking interferes with the vitamin. The 2014 Ludhiana report calls pellagra increasingly rare but still endemic among maize-eating populations of India, and a 2021 review in the Indian Journal of Medical Research names maize, jowar and bajra eaters as the groups in whom dietary deficiency arises. WHO records outbreaks since 1988 among refugees and displaced people.

The FAO and WHO consultation adds medical causes: chronic alcoholism, Crohn's disease, and rare conditions that disturb the handling of tryptophan, such as Hartnup disease and carcinoid syndrome. Shortages of riboflavin and vitamin B6 may contribute as well. This entry found no national survey of niacin status in India, so how common a mild shortfall is today cannot be stated.

What does the evidence say about high-dose niacin for the heart?

That it does not help, and that it causes harm. Nicotinic acid in gram doses lowers LDL cholesterol and raises HDL cholesterol, which is why it was tested as a heart drug. A Cochrane review in 2017 pooled 23 randomised trials with 39,195 participants, in which the median dose was 2 g a day, more than 140 times the dietary allowance. Niacin did not reduce overall deaths, cardiovascular deaths, heart attacks or strokes, on moderate to high quality evidence, and people taking it were about twice as likely to stop treatment because of side effects.

The largest single trial, HPS2-THRIVE, randomised 25,673 adults with vascular disease who were already on statin-based treatment. Over a median of 3.9 years, major vascular events occurred in 13.2 per cent on niacin with laropiprant and 13.7 per cent on placebo, a difference that was not significant. The niacin group had more serious disturbances of diabetes control and more serious gastrointestinal, muscle, skin, infection and bleeding events. Cholesterol is managed by a doctor, with food playing the part set out in the Indian cholesterol diet chart.

Flushing and other side effects of too much niacin

ICMR-NIN sets the tolerable upper limit at 35 mg a day for adult men and women, the figure the FAO and WHO consultation also adopted, and enters no figure for children, pregnancy or lactation. Food does not approach it. The best-known effect of larger amounts is flushing: a review of the mechanism explains that nicotinic acid acts on cells in the skin to release prostaglandins, which widen the small blood vessels there. The consultation adds that long-term high oral doses can injure the liver.

Tablets are where the limit gets crossed. The 2021 Indian review found that the five most popular B-complex products in the country held 45 to 100 mg of niacin each, above the 35 mg limit, though it does not say in which form; the article on vitamin B complex tablets explains what else is in a strip. High-strength nicotinic acid for cholesterol is a medicine and should not be self-prescribed.

A rash on sun-exposed skin together with diarrhoea, a sore mouth or confusion needs a doctor promptly, not a tablet from the chemist. In the Ludhiana case the diagnosis rested on the clinical picture and treatment was supervised. Do not start, stop or change a prescribed medicine on the strength of this page.

A worked example: counting niacin equivalents for a vegetarian day

This case is illustrative and describes no real person. A 35-year-old vegetarian bank clerk in Kolkata, sedentary, has an allowance of 14 mg. His day: poha (60 g, 0.96 mg) with groundnuts (15 g, 1.70 mg) at breakfast; rice (100 g raw, 1.69 mg), whole masoor (30 g, 0.76 mg) and potato (100 g, 1.04 mg) at lunch; three chapatis (90 g atta, 2.13 mg), moong dal (30 g, 0.55 mg) and a glass of milk (200 g, 0.16 mg) at night. Preformed niacin comes to about 9.0 mg, close to the 10 mg that Indian diet surveys report.

Two cautions apply. The 60 to 1 factor is an average with wide individual variation, and the tryptophan in poha and potato was left out. Take away the dal, the milk and the groundnuts, and both columns fall together: that is the single-cereal diet in which pellagra used to appear.

Common mistakes and myths about niacin

The first mistake is to read a food table's niacin column as the whole story, when milk and dal add niacin through tryptophan. The second is to take nicotinic acid for cholesterol on a relative's advice; the trials above found no benefit and real harm. The third is to treat a flush as a sign that a product is working, when it is a side effect.

Learning this properly

The B vitamins, niacin among them, belong to NNWA's teaching on requirements and deficiency diseases. NNWA is a private skill academy based in Kolkata that teaches online in English and Hindi. Its courses prepare learners to coach healthy people and to refer anyone with a medical condition; they are not degrees and do not make anyone a dietitian. The Clinical Nutrition course covers deficiency signs and referral, and the Diploma in Nutrition, Dietetics and Public Health covers requirements.