Vitamin C (Ascorbic Acid): ICMR-NIN Values by Age, Indian Sources, Cooking Losses and Iron Absorption

Vitamin C, also called ascorbic acid, is a water-soluble vitamin that humans cannot make and so must eat. The body uses it to form collagen, the structural protein of skin, gums, blood vessels and bone, and it helps the gut take up iron from plant foods. ICMR-NIN's Nutrient Requirements for Indians 2020 sets the allowance at 80 mg a day for an adult man and 65 mg for an adult woman. This entry in the vitamins section of the handbook gives the values for every age, the Indian foods that supply them, and what cooking does to the vitamin.

What does vitamin C do in the body?

It gives up electrons easily, which is the chemistry behind the word antioxidant. The joint FAO and WHO expert consultation on vitamin requirements counts eight human enzymes that depend on it, three of them in building collagen and two in making carnitine. ICMR-NIN's 2024 Dietary Guidelines put it plainly: vitamin C is an essential nutrient required for healthy bones and teeth, and it promotes iron absorption.

Most animals make their own vitamin C from glucose; humans, other primates and guinea pigs cannot. A well-fed adult holds about 1,500 mg in the body, and during depletion roughly 3 per cent of that store is lost each day. Hence the consultation's point that regular intake matters more than how rich any one food is.

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

An adult man needs 80 mg a day and an adult woman 65 mg. Those are recommended allowances, set at the top end of the range of individual needs. The estimated average requirement, the median need, is 65 mg and 55 mg. The expert group worked from a saturated body pool of 900 mg, a metabolic loss of 2.9 per cent a day, and the absorption seen from Indian foods. Pregnancy takes the allowance to 80 mg and breastfeeding to 115 mg.

Two things stand out. The upper limit for children is low and climbs with age, from 350 mg at 1 to 3 years to 2,000 mg for girls of 16 to 18, which matters when chewable tablets are handed to a small child. And the Indian allowance is well above the 45 mg a day that the FAO and WHO consultation recommended for adults: expert groups working from different criteria reach different numbers.

Which Indian foods give the most vitamin C per portion?

Amla and guava lead by a wide margin, followed by capsicum, drumstick leaves and the citrus fruits. The table turns the per 100 g values of the Indian Food Composition Tables 2017 into ordinary helpings. Every figure is for the raw food, and the portion weights are round working numbers, so weigh your own fruit if you need precision. The ranked list of all foods is in the vitamin C table of Indian foods.

A single guava or 50 g of amla covers an adult's day more than once; the amla page and the comparison of guava and orange show the rest of their panels. Cauliflower and potato hold useful amounts when raw, but they are eaten cooked. And the staples bring next to nothing: the Indian tables print no vitamin C value at all for milled rice, atta or the common dals, and a glass of milk has 4 mg.

Cooking, cutting and storage: where the vitamin goes

ICMR-NIN's 2024 guidelines say it is very susceptible to destruction by oxidation in air, so that when vegetables turn dry and stale, or are cut and left exposed, or are cooked, most of the vitamin originally present is destroyed. The FAO and WHO consultation supplies the detail: cutting or bruising releases an enzyme that breaks ascorbate down, heat destroys it, contact with copper or iron and mildly alkaline conditions add to the loss, and too much water leaches it out of the tissue.

Time matters more than technique. The guidelines state that cooking time affects vitamin C losses more than the cooking method does, that the vitamin goes down the drain when cooking water is discarded, and that steaming and microwave cooking, which need little water and little time, keep more of it. Storage counts as well: the consultation cites potatoes falling from 30 mg to 8 mg per 100 g over eight to nine months in store. No single percentage fits every kitchen, so none is quoted here.

How does vitamin C help iron absorption?

It holds the iron of plant foods in a form the gut can take up, and it does so at food-level amounts, provided it is eaten in the same meal. The FAO and WHO consultation puts the amount needed to raise iron absorption at 25 mg upwards, depending on how much phytate and polyphenol the meal contains. For this reason ICMR-NIN's 2020 report recommends at least 20 mg of vitamin C for every 1,000 kcal of the diet, which works out to about 33 mg for a woman eating 1,660 kcal.

A stable-isotope study at St John's Research Institute in Bengaluru measured the effect in young women eating a rice meal. Ascorbic acid added at twice the molar amount of the iron raised absorption by 270 per cent in iron-replete women and by 291 per cent in those with iron deficiency anaemia; at four times the molar amount the rises were 343 and 350 per cent. Black tea taken alongside pulled absorption down. The iron entry covers the tea side, and a sprouts salad with lemon puts both nutrients in one bowl.

Too little vitamin C: scurvy and the Indian evidence

Severe deficiency is scurvy. The FAO and WHO consultation lists swollen or bleeding gums, pinpoint bleeding under the skin, joint pain and slow wound healing, with anaemia a common feature and, in infants, painful limbs. Signs appear in men at intakes below about 10 mg a day, once the body's content has fallen under 300 mg, and a person who starts with full stores can go roughly two months without the vitamin before they show.

Milder shortage is harder to see and may be common. A population study published in 2011 measured plasma vitamin C in 5,638 people aged 60 and over at one centre in north India and one in the south. Deficiency, defined as less than 11 micromoles per litre, was found in 73.9 per cent of the northern group and 45.7 per cent of the southern; only 10.8 and 25.9 per cent had adequate levels. It was more frequent in men, with rising age, and in users of tobacco and biomass cooking fuel, and it varied with the season.

Those figures come from two poor communities and cannot stand for the whole country, and the table of children's deficiencies that ICMR-NIN's 2024 guidelines reproduce from the 2019 national nutrition survey has no line for vitamin C. On tobacco, the consultation records that turnover of the vitamin in smokers was 50 per cent greater than in non-smokers.

What does the evidence say about vitamin C tablets?

For the common cold the evidence is large and the answer is mostly no. The Cochrane review of 2013 pooled 29 trial comparisons with 11,306 participants, all using at least 200 mg a day. Regular tablets did not reduce the number of people catching a cold in the general community. They shortened colds a little, by 8 per cent in adults and 14 per cent in children, and tablets started after symptoms began showed no consistent effect. Only among 598 marathon runners, skiers and soldiers under heavy physical stress was the risk of a cold about halved.

For long-term health the trials are flat. A Cochrane review of antioxidant supplements, covering 78 randomised trials and 296,707 participants, found no effect of vitamin C on deaths from any cause across 29 trials (risk ratio 1.02, with a confidence interval that includes no effect). The FAO and WHO consultation makes a matching observation: diets high in vitamin C go with better health in population studies, but intervention studies do not bear the association out. ICMR-NIN's report asks instead for at least 500 g of fruit and vegetables a day. The article on whether a vitamin C tablet is needed or food will do follows the tablet question further.

A worked example: one vegetarian day counted

This is an illustration, not a real person. Take a 34-year-old vegetarian schoolteacher in Pune, whose allowance is 65 mg. Her day has poha with a tablespoon of lemon juice squeezed on at the table (7 mg), a cauliflower and potato sabzi at lunch made from 100 g of each (47 mg and 23 mg when raw), a tomato in the dal (100 g, 27 mg raw) and a banana (5 mg). On raw weights that adds up to 109 mg, which looks comfortable.

The raw total misleads, because 97 mg of it sits in food that will be cooked. Suppose half of that is lost in the pan; the half is an assumption made for the arithmetic, not a measured figure. The cooked vegetables then give about 49 mg, and with the lemon and the banana the day comes to roughly 61 mg, a little under her allowance. One orange of 150 g, eaten raw after lunch, adds 64 mg and settles it. The decision in this example is not a tablet. It is one raw fruit a day.

Common mistakes and myths about vitamin C

The second mistake is to read a food table as though it described the cooked dish. The third is to pour lemon juice into dal that is still boiling, when the heat will destroy part of it. The fourth is to think of amla as a once-a-season tonic, when the body's store runs down by about 3 per cent a day without intake. The fifth is to assume that more is always better.

Too much vitamin C, side effects and when to see a doctor

ICMR-NIN's tolerable upper limit is 2,000 mg a day for adults, pregnant and breastfeeding women included, counted as habitual intake from all sources. Food cannot realistically reach it. Tablets can. The FAO and WHO consultation reports that 2 to 3 g a day produces diarrhoea in most people, that stomach upset can follow as little as 1 g because about half of such a dose is not absorbed, and it judged 1 g to be the advisable upper limit of intake.

Kidney stones are the other concern, because oxalate is an end product of vitamin C breakdown. In American cohorts of 156,735 women and 40,536 men followed for more than 11 years, men whose total intake was 1,000 mg a day or more had a 43 per cent higher risk than men taking under 90 mg. No link was seen in women, and vitamin C from food alone was not associated with stones in either sex. This is observational evidence of an association, not proof of cause.

The consultation also notes that vitamin C may set off the breakdown of red blood cells in some people, among them those with G6PD deficiency. FSSAI's fortification standards deal in food-level amounts: fortified fruit juice must carry 6 to 12 mg of vitamin C per 100 ml.

Learning this properly

Vitamin C comes up in NNWA's teaching under micronutrients, food science and meal planning. NNWA 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 deals with nutrient requirements across the life stages, and the Public Health Nutrition course with how deficiency is surveyed and addressed in populations.