Vitamin B6 (Pyridoxine): ICMR-NIN Requirement, Indian Sources, Upper Limit and Nerve Damage

Vitamin B6 is a group of three related compounds, of which pyridoxine is the one sold in tablets. The body uses it mainly to handle the amino acids that protein is built from. ICMR-NIN's Nutrient Requirements for Indians 2020 sets the recommended allowance at 1.9 mg a day for a sedentary adult of either sex and the tolerable upper limit at 100 mg. It has a recognised harm at high doses: lasting intake far above need can injure the sensory nerves. This entry in the vitamins section of the handbook gives the figures.

What does vitamin B6 do in the body?

It is the working part of enzymes that reshape amino acids. The joint FAO and WHO expert consultation on vitamin requirements explains that the three natural forms, pyridoxine, pyridoxamine and pyridoxal, are converted in the body to pyridoxal phosphate, which serves the enzymes of amino acid metabolism and also takes part in making haem for blood and in breaking down glycogen. The consultation puts the bioavailability of vitamin B6 from a mixed diet at about 75 per cent.

B6 does not act alone. The same consultation notes that riboflavin is needed to form the active co-enzyme, so a shortage of one tends to travel with a shortage of the other, and that B6 is required for the body's conversion of the amino acid tryptophan to niacin. When B6 is short, homocysteine in the blood rises, as it does with low folate status or vitamin B12. The entry on riboflavin covers the partner vitamin.

How much vitamin B6 do you need under ICMR-NIN's 2020 values?

A sedentary man or woman needs 1.9 mg a day on the recommended allowance and 1.6 mg on the estimated average requirement. The expert group derived the adult figure from studies of a B6-dependent enzyme in red blood cells, arrived at an average requirement of 1.6 mg, and extended it to other ages, activity levels and life stages in proportion to energy needs. That is why the values for adolescent boys and for men doing heavy work are the highest in the table.

Two details stand out. The report prints the same value for a sedentary and a moderately active woman, 1.9 mg, while a man's allowance steps up from 1.9 to 2.4 mg between those levels. And nowhere does the need pass about 3 mg a day.

Which Indian foods supply vitamin B6?

B6 is spread thinly across many foods, with chicken, fish, bananas, green leaves, millets, whole pulses and nuts giving the most in a helping. ICMR-NIN's 2024 Dietary Guidelines put the average at about 311 mcg per 100 g for nuts, 220 mcg for meat and poultry, 216 mcg for pulses and 162 mcg for cereals, against 16 mcg for milk. The portions below are calculated from the Indian Food Composition Tables 2017, with grains and pulses at their raw weight; the vitamin B6 table of Indian foods ranks them per 100 g.

The pattern differs from the other B vitamins. Ragi has almost no B6, and split dals hold less than the whole pulse: masoor dal has 0.18 mg per 100 g and whole masoor 0.46 mg. Milling costs rice two thirds of its B6, from 0.37 mg per 100 g in brown rice to 0.12 mg in raw milled rice. A banana is the easiest single addition, and the comparison of banana and apple shows its other nutrients.

How common is low vitamin B6 in India?

The one detailed Indian study suggests it is common among city adults, though it covers a single city. Researchers at the National Institute of Nutrition measured blood vitamins in 270 apparently healthy adults aged 30 to 70 in Hyderabad. Low B6 status was found in 46 per cent, second only to riboflavin at 50 per cent, and only 30 per cent of participants were judged likely to be eating enough B6. High homocysteine was present in 52 per cent. None of the sources used for this entry gives a national figure.

Low status is not the same as illness. The FAO and WHO consultation observes that deficiency of B6 by itself is uncommon, because it usually arrives with shortages of other B vitamins. When it does show, the signs it lists are skin changes with cracked lips and a sore tongue, a fall in circulating lymphocytes, sometimes anaemia, and in infants convulsions. It also describes low intakes as widespread among people who eat poorly, and notes deficiency in people on long-term haemodialysis.

Too much vitamin B6: the upper limit and nerve damage

The harm of excess B6 was first described in 1983, when doctors reported seven adults who developed unsteadiness and severe loss of sensation after taking large daily amounts of pyridoxine. Four were severely disabled, and all improved once they stopped. The FAO and WHO consultation later recorded that high doses taken for premenstrual syndrome, carpal tunnel syndrome and some neurological diseases had resulted in nerve toxicity, and adopted an upper level of 100 mg a day. ICMR-NIN's 2020 table lists the same 100 mg for adult men and women.

The European figure is the newest and by far the lowest. Its panel called the link between excess B6 and peripheral neuropathy well established, took 50 mg a day as its reference point from a case-control study, and divided by an uncertainty factor of 4 because symptoms take longer to appear at lower doses and the data are limited. For children it derived limits of 3.2 to 4.5 mg at 1 to 6 years and 6.1 to 10.7 mg at 7 to 17 years. Food was not the worry: only regular users of high-dose supplements were likely to exceed the limit.

What does the evidence say about vitamin B6 supplements?

The largest body of trials tested B6 with folic acid and B12 to lower homocysteine and prevent heart disease. A Cochrane review updated in 2017 pooled 15 randomised trials with 71,422 participants and found no difference from placebo in heart attacks or in deaths from any cause, on high-quality evidence. Stroke was slightly less frequent, 4.3 per cent against 5.1 per cent. The authors judged that further trials were unlikely to change the picture.

Two popular uses rest on weaker ground. A Cochrane review of remedies for nausea and vomiting in early pregnancy, covering 41 trials and 5,449 women, found only limited evidence for vitamin B6 and no high-quality evidence for any single intervention. A 1999 systematic review of 9 trials with 940 women found B6 better than placebo for premenstrual symptoms, with an odds ratio of 2.32, but said its conclusions were limited by the low quality of most trials. Both questions belong with a doctor.

A worked example: counting a vegetarian day

This is an illustration, not a real person. Take a 34-year-old vegetarian software engineer in Pune, sedentary, with an allowance of 1.9 mg and an average requirement of 1.6 mg. His day: poha at breakfast (60 g, 0.01 mg of B6); two chapatis (0.15 mg), toor dal (30 g, 0.07 mg), potato sabzi (100 g, 0.10 mg) and rice (75 g raw, 0.09 mg) at lunch; a glass of milk (0.08 mg); rice (0.09 mg), moong dal (30 g, 0.06 mg) and palak (100 g, 0.15 mg) at dinner. The total is about 0.8 mg, half the average requirement.

Now the changes. A banana adds 0.44 mg. Methi in place of palak adds 0.23 mg, whole masoor in place of moong dal 0.08 mg, a tablespoon of sunflower seeds 0.14 mg, and two jowar rotis in place of the dinner rice 0.08 mg. The day reaches about 1.8 mg, above the average requirement and close to the allowance. The gap that food had to close was about 1 mg. A tablet of 50 mg, the European panel's reference point for nerve effects, would be 26 times the daily allowance.

Common mistakes and myths about vitamin B6

The second mistake is stacking: a B-complex, a multivitamin and a separate nerve product taken together, each adding its own pyridoxine. The third is to treat tingling in the feet as a reason to take more B vitamins, when excess B6 is itself a cause of sensory nerve damage. The fourth is to assume a vegetarian diet must be short of B6; greens, bananas, millets and whole pulses supply it. The articles on B-complex tablets and on whether a multivitamin is needed go further.

Who should see a doctor before taking vitamin B6?

Anyone planning to take a separate B6 product every day should ask first, and some people should not start without advice at all. ICMR-NIN's table gives no upper limit for pregnancy, lactation or childhood, so there is no Indian figure to lean on for those groups, while the European limit of 12 mg covers pregnant and breastfeeding women. A product recommended for morning sickness or period symptoms should come from the doctor managing the pregnancy or the symptoms, with the dose and the duration stated.

If nerve symptoms appear while you are taking a supplement that contains B6, show the doctor every product you use; in the 1983 report all seven people improved after the vitamin was withdrawn. Food carries no such risk: the best everyday sources hold under 1 mg in a helping, and the pregnancy diet guide shows how a full day's eating covers the vitamins of that stage.

FSSAI's fortification standard for vitamin B6

India's fortification regulations treat B6 as an optional extra. Fortified atta, maida and rice must contain added iron, folic acid and vitamin B12, and may also be fortified with pyridoxine hydrochloride at 1.5 to 2.5 mg per kg. In kitchen terms that is 0.09 to 0.15 mg in the 60 g of atta that makes two chapatis, at most as much again as the flour holds naturally. Each pack of fortified food has to carry the words fortified with, followed by the name of the fortificant, and the official logo.

Learning this properly

NNWA teaches vitamin B6 within its units on water-soluble vitamins, protein metabolism and supplement safety. It is a private skill academy in Kolkata with online classes in English and Hindi; the courses equip people to coach healthy clients and to pass medical cases to a doctor, and no course is a degree or a dietitian qualification. The Clinical Nutrition and Dietetics course deals with deficiency and excess in illness, and the Diploma in Nutrition, Dietetics and Public Health covers requirements and meal planning.