Riboflavin (Vitamin B2): ICMR-NIN Requirement, Milk and Millet Sources, and Angular Stomatitis

Riboflavin is vitamin B2, a water-soluble vitamin that the body converts into two coenzymes, FMN and FAD, which help release energy from carbohydrate, fat and protein. ICMR-NIN's Nutrient Requirements for Indians 2020 sets the recommended allowance at 2.0 mg a day for a sedentary man and 1.9 mg for a sedentary woman, rising with physical work, pregnancy and breastfeeding. Milk, green leafy vegetables, millets and whole pulses are the main Indian sources. This entry in the vitamins section of the handbook sets out the values, the foods and the signs of a shortfall.

What does riboflavin do in the body?

It works as a helper for enzymes. The joint FAO and WHO expert consultation on vitamin requirements describes how riboflavin is converted to flavin mononucleotide (FMN) and then to flavin adenine dinucleotide (FAD), and how these coenzymes take part in oxidation and reduction reactions and in energy production. ICMR-NIN's 2024 Dietary Guidelines also list riboflavin, with vitamins C and E, among the antioxidants that protect the body from free radical damage.

Riboflavin also keeps two other B vitamins working. The same consultation notes that FAD is needed to form niacin from the amino acid tryptophan, as the handbook's entry on niacin and its equivalents explains, and that FMN is needed to activate vitamin B6. The body holds little in reserve: the 2024 guidelines point out that water-soluble vitamins, apart from B12 and folate, are not stored and are easily lost in urine.

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

A sedentary man needs 2.0 mg a day and a sedentary woman 1.9 mg on the recommended allowance, with an estimated average requirement of 1.6 mg for both. The allowance climbs with physical work, to 3.2 mg for a man and 3.1 mg for a woman doing heavy work. Pregnancy takes it to 2.7 mg and the first six months of breastfeeding to 3.0 mg. The table gives both values for each group.

The expert group reached these figures by plotting a blood test, the erythrocyte glutathione reductase activity coefficient, against riboflavin intake and taking 1.2 as the acceptable cut-off. The result is higher than before: ICMR-NIN's brief note shows the allowance for the reference man rising from 1.6 mg in the 2010 edition to 2.5 mg in 2020. It also sits well above the FAO and WHO recommended intake of 1.3 mg for men and 1.1 mg for women. The 2020 table of upper limits has no entry for riboflavin.

Which Indian foods supply riboflavin?

Milk, green leafy vegetables, millets, whole pulses, eggs and liver supply most of it, though no everyday food is a concentrated source. The portions below are worked out from the per 100 g figures in ICMR-NIN's food composition tables of 2017, using raw weights for grains and pulses. The riboflavin table of Indian foods ranks every food in the database, so this list stays with what turns up in an ordinary kitchen.

Two things stand out. A glass of milk gives more riboflavin than two chapatis and a katori of toor dal together, which is why milk carries so much of the load in vegetarian diets; the comparison of cow and buffalo milk has the full panels. And polished rice gives almost none. Bajra and ragi hold three to four times as much, weight for weight, as the ragi nutrition page shows, and drumstick leaves are among the richest greens.

Can an Indian vegetarian diet reach the allowance from food alone?

Only just, and often not. ICMR-NIN's 2020 report prints model balanced diets with their nutrient content, and riboflavin is one nutrient where the model falls short of the allowance. The vegetarian diet for a sedentary woman, with 300 g of milk and 100 g of green leafy vegetables a day, supplies 1.5 mg against an allowance of 1.9 mg. For a sedentary man it supplies 1.6 mg against 2.0 mg, and for a pregnant woman 1.8 mg against 2.7 mg.

Read those figures with care. The same report says the diet of a population should be planned on the average requirement, and the sedentary diets sit at or near that 1.6 mg. Falling below the allowance on paper is not the same as being deficient, but it shows how little slack there is when a household buys less milk and fewer greens than the model.

Angular stomatitis and the other signs of too little

Riboflavin deficiency, called ariboflavinosis, shows first in the mouth and skin. The FAO and WHO consultation lists sore throat, a red and swollen lining of the mouth, cheilosis (cracked lips), angular stomatitis (cracks at the corners of the mouth), glossitis (a sore, inflamed tongue) and a scaly dermatitis. It adds that the deficiency almost always arrives with a shortage of other B vitamins, so some signs may have more than one cause.

Indian school surveys have long recorded these signs. A study of schoolboys in villages around Hyderabad, published in 1979, found angular stomatitis in 41.3 per cent and glossitis in 18.2 per cent, and almost all the boys were riboflavin deficient on an enzyme test. A month of B-complex vitamins reduced glossitis but had no effect on angular stomatitis. In a small 2009 study in two Chennai schools, by contrast, angular stomatitis fell from 21 per cent to none where the noon meal was fortified with iron and riboflavin, and stayed near 20 per cent in the other school.

Who is most at risk of riboflavin deficiency in India?

People who take little milk and few greens, and women who are pregnant or breastfeeding, whose needs are highest. A 2019 study from the National Institute of Nutrition tested the blood of 270 apparently healthy adults aged 30 to 70 in Hyderabad and found vitamin B2 deficiency in 50 per cent, the highest figure among the vitamins measured. It was one city and an exploratory study, so it is a warning sign and not a national estimate.

The FAO and WHO consultation gives further causes. Lactose intolerance can cut milk intake, and tropical sprue, coeliac disease and surgery on the small bowel reduce absorption. A breastfeeding mother's status passes to her child: the consultation cites low-income Indian women whose milk held 0.22 mg of riboflavin a litre against an average of 0.35 mg. If milk does not suit you, the guide to eating with lactose intolerance lists what to use instead.

Does fortified atta or rice add riboflavin under FSSAI rules?

It can, but only if the maker chooses to add it. FSSAI's fortification regulations require fortified atta, maida and rice to carry iron, folic acid and vitamin B12, and allow riboflavin as an optional extra at 1.25 to 1.75 mg per kg. At that level, 60 g of fortified atta, about two chapatis, would add roughly 0.08 to 0.11 mg. A pack marked as fortified need not contain B2, so read the panel to see what was added.

What does the evidence say about riboflavin supplements?

Two trials are worth knowing, and neither is a reason to self-prescribe. In the United Kingdom, 123 women aged 19 to 25 with biochemical riboflavin deficiency took riboflavin or a placebo for 8 weeks. The rise in haemoglobin tracked the improvement in riboflavin status, most of all in the women who began with the poorest status, while iron intake and absorption did not change. It is one trial of moderate size, so the evidence is suggestive; the handbook's iron entry covers anaemia itself.

The second, in Northern Ireland, studied 91 people with high blood pressure who carried two copies of the MTHFR 677T gene variant. After 16 weeks, systolic pressure was 5.6 mmHg lower with riboflavin than with placebo. The finding applies to that genotype only, and nobody should adjust blood pressure treatment on the strength of it. Trials in migraine have used about two hundred times the dietary allowance, which is drug-level use and a question for a neurologist.

For healthy adults the picture is plainer. A 2022 meta-analysis of nine migraine trials with 673 people is the main support for high-strength riboflavin, and its results differed widely between trials. A 2021 review in the Indian Journal of Medical Research concluded that the evidence discourages routine B vitamin supplements in the well nourished.

A worked example: one vegetarian day in Pune

This is an illustration, not a real person. Take a 30-year-old vegetarian schoolteacher in Pune whose work counts as sedentary, so her allowance is 1.9 mg and the average requirement 1.6 mg. Her usual day is poha at breakfast (60 g, 0.02 mg), two cups of tea with 50 g of milk each (0.11 mg), two chapatis (0.09 mg), toor dal (30 g, 0.03 mg) and potato sabzi (100 g, 0.01 mg) at lunch, and rice (75 g, 0.04 mg) with moong dal (30 g, 0.04 mg) at dinner. These main items add up to about 0.34 mg.

Four sensible changes more than double her intake, yet the main items still reach only about half the average requirement of 1.6 mg. Fruit, other vegetables, nuts and spices, left out here, add a little more. Milk and green leafy vegetables move the total far more than changing the cereal or the dal. It is arithmetic, not a diagnosis, and a low number on paper is no reason to start tablets.

Common mistakes and myths about riboflavin

The first mistake is to treat a B-complex strip as a harmless daily tonic; the article on vitamin B complex tablets explains who has a real reason to take one. The second is to assume that rice and dal cover the B vitamins, when milled rice holds 0.05 mg of riboflavin per 100 g. The third is to drop milk and replace it with nothing.

Too much riboflavin, safety and when to see a doctor

ICMR-NIN's 2020 table of tolerable upper limits has no entry for riboflavin, and the FAO and WHO consultation says toxicity is not a problem because the gut absorbs only a limited amount, about 27 mg from a single meal or dose. That does not make large tablets useful. The 2021 Indian review found that the five most popular B-complex products in the country each held 10 mg of riboflavin, about five times the allowance, an amount it classed as a treatment dose.

Anyone with a diagnosed illness or on long-term medicines should ask their doctor before adding a B-complex tablet, and should not change a prescribed medicine because of anything read here. Riboflavin status is measured by a specialised enzyme test whose results, the FAO and WHO consultation notes, are confounded in G6PD deficiency and beta thalassaemia trait, so reading it is a doctor's job.

Learning this properly

NNWA teaches riboflavin with the other B vitamins. It is a private skill academy in Kolkata that teaches online in English and Hindi; its courses train people to coach healthy clients and to refer medical cases, and none is a degree or a dietitian qualification. The Diploma in Nutrition, Dietetics and Public Health covers the vitamins and life-stage needs, and the Public Health Nutrition course looks at surveys and fortification.