Magnesium: ICMR-NIN Requirement by Age, Indian Food Sources, Supplement Forms and the Laxative Limit

Magnesium is a mineral the body uses in hundreds of enzyme reactions, many of them concerned with releasing energy from food, and it is among the most abundant minerals inside cells. ICMR-NIN's Nutrient Requirements for Indians sets the recommended allowance at 440 mg a day for an adult man and 370 mg for an adult woman. The food sources are ordinary ones: whole grains, millets, pulses, nuts, seeds and green leaves. This entry in the minerals section of the handbook gives the values for every age, the amounts in Indian portions, and what is known about the tablets.

What does magnesium do in the body?

It works as a helper for enzymes. The European Commission's Scientific Committee on Food, in its 2001 opinion on magnesium, describes it as a cofactor in hundreds of enzymatic reactions, many involving energy metabolism, with a part in making protein and nucleic acids and in keeping calcium, potassium and sodium in balance. The same opinion puts the magnesium in a healthy adult body at about 21 to 28 g.

Very little of that store is in the blood: the committee notes that serum magnesium represents only about 0.3 per cent of the body's total, which is why the test is read by a doctor alongside calcium and potassium. The gut and kidneys do the balancing. Absorption runs at about 30 to 40 per cent of intake and can rise to as much as 80 per cent when the diet is low, and healthy kidneys cut the amount lost in urine to a tenth within a few days.

How much magnesium do you need under the Indian values?

An adult man needs 440 mg a day and an adult woman 370 mg on the recommended allowance, which covers nearly every healthy person. The estimated average requirement, the figure used to judge a group's diet, is 370 mg and 310 mg. ICMR-NIN's expert group arrived at these from balance studies: the intake at which the body neither gains nor loses magnesium worked out at 368 mg a day once absorption was allowed for, was rounded to 370 mg for men, and was scaled by body weight for everyone else.

The upper limit of 350 mg is lower than a man's allowance, which can look like a misprint. The report states that the limit applies to non-dietary pharmacological doses only, meaning tablets, powders and antacids; magnesium eaten in food does not count towards it. The allowance itself went up in 2020: the expert group's own comparison shows 340 mg for men and 310 mg for women in the 2010 edition.

Which Indian foods supply the most magnesium per portion?

Seeds, nuts, millets, whole pulses and dark green leaves lead, and a normal helping of any of them gives 50 to 100 mg. The table turns the per 100 g values of the Indian Food Composition Tables 2017 into household portions, using raw weights for grains and pulses. For the ranked figures across every food group, see the magnesium table of Indian foods.

The bottom of the table explains most low intakes. Milling strips the magnesium out with the bran: the Indian tables give 125 mg per 100 g for atta against 31 mg for maida, and 94 mg for brown rice against 19 mg for milled rice. A plate built on white rice, maida and milk starts far behind one built on atta in place of maida or on millets such as ragi and jowar. Cooking helps a little: ICMR-NIN's 2024 guidelines say boiling and pressure cooking greatly reduce the phytic acid that binds minerals in cereals and legumes.

Magnesium intake in India: the gaps in the evidence

There is no national figure for magnesium status in India. The large surveys that report anaemia and iodised salt, including the National Family Health Survey of 2019-21, do not measure it, so nobody can say what share of Indians fall short. What exists is arithmetic. ICMR-NIN's annexures set out model balanced diets built on whole grains, pulses, vegetables and nuts, and each supplies 500 mg of magnesium or more. The risk lies in how far a real diet has drifted from that model, as the comparison of brown rice and white rice shows for one swap.

Too little magnesium: causes and signs

Outright deficiency from diet alone is uncommon in a healthy adult because the kidneys hold magnesium back when intake falls. It appears when losses rise. The European committee lists diarrhoea and bowel disease, which reduce absorption, and conditions that increase loss in urine: diabetes with heavy urination, most diuretics and alcohol. Acid-suppressing medicines belong on the list too. A 2015 meta-analysis of nine observational studies covering 109,798 patients found low blood magnesium 1.43 times as common in people taking proton pump inhibitors.

The signs are mainly of nerves and muscles, and the committee notes that low magnesium is often accompanied by low blood calcium, which is why this entry and the entry on calcium belong together. None of the signs is specific, and cramps or tiredness have many commoner causes, so a suspicion of deficiency is settled by a doctor's examination and blood tests.

Which form of magnesium supplement is absorbed best?

The soluble salts are absorbed better than magnesium oxide, the cheapest and most common form. A study of four commercial preparations in healthy volunteers found a fractional absorption of only 4 per cent for the oxide, with magnesium chloride, lactate and aspartate significantly higher and equal to one another. An earlier study found the citrate more soluble and better absorbed than the oxide. Both were small and measured magnesium in urine, so they rank the forms without proving that one works better for any complaint.

FSSAI's health supplement regulations, in the 2021 compendium, list eight magnesium compounds that may be used: aspartate, carbonate, chloride, gluconate, two phosphates, oxide and sulphate. They say that added nutrients shall not exceed the recommended daily allowance set by the Indian Council of Medical Research, and that the pack must carry the words HEALTH SUPPLEMENT, the advisory NOT FOR MEDICINAL USE and a warning not to exceed the stated daily usage.

Why do magnesium tablets cause loose stools?

Because unabsorbed magnesium salts draw water into the bowel. The European committee calls this an osmotic effect and describes it as dose-dependent: across the trials it reviewed, no laxative effect was seen at up to 250 mg of supplemental magnesium a day, while mild diarrhoea appeared in a small percentage of adults at about 360 mg. It set its own upper level for supplements at 250 mg on that basis, lower than ICMR-NIN's 350 mg. Both bodies agree on the essential point, that magnesium in food has not been shown to cause diarrhoea.

The committee adds that a day's dose is better tolerated when divided, that the bowel adapts over days, and that the effect reverses when the supplement stops. In the Cochrane review of magnesium for muscle cramps, gastrointestinal complaints such as diarrhoea affected between 11 and 37 per cent of people taking oral magnesium, against 10 to 14 per cent of those on placebo.

What does the evidence say about magnesium and health?

The strongest signal is observational. A 2016 dose-response meta-analysis of 40 prospective cohort studies with more than 1 million participants found that each extra 100 mg of dietary magnesium a day was associated with a 19 per cent lower risk of type 2 diabetes, 7 per cent lower risk of stroke and 22 per cent lower risk of heart failure, with no association for coronary heart disease or cardiovascular disease as a whole. People who eat more magnesium also eat more whole grains, pulses and fibre, so this is evidence for the diet, not for a tablet.

Trials of supplements show smaller effects. A meta-analysis of 34 randomised, double-blind, placebo-controlled trials in 2,028 adults found that a median 368 mg a day for a median three months lowered systolic blood pressure by 2.00 mm Hg and diastolic by 1.78 mm Hg. That is a modest change, at a dose above the supplement limit. For cramps, the Cochrane review of 11 trials and 735 people concluded that magnesium is unlikely to give meaningful protection to older adults, and that the trials in pregnancy conflict.

A worked example: one vegetarian day, before and after

This is an illustration, not a real person. Take a 31-year-old vegetarian accountant in Pune whose allowance is 370 mg. Her usual day has bread or a maida paratha at breakfast (60 g maida, 18 mg), rice at lunch and dinner (75 g raw each time, 14.5 mg each), toor dal at lunch (30 g, 36 mg), moong dal at dinner (30 g, 47 mg), two glasses of milk (32 mg) and a banana (35 mg). The total is about 197 mg, a little over half the allowance and well under the average requirement of 310 mg.

Three changes close the gap. Ragi dosa or ragi roti at breakfast in place of maida (60 g, 88 mg) adds 70 mg. Two chapatis at dinner in place of rice (60 g atta, 75 mg) add about 60 mg. A handful of peanuts in the evening (30 g) adds 59 mg. The day now reaches about 385 mg without a supplement, and a katori of palak twice a week takes it higher. The weights are raw, so treat the sums as a guide to proportion.

Common mistakes and myths about magnesium

The second mistake is to read the weight of the compound on the pack as the magnesium inside, when the two absorption studies above show that the amount reaching the blood differs again. The third is to take a magnesium antacid with an iron tablet: in one crossover study of 13 men, magnesium hydroxide taken an hour after iron cut iron absorption by 46 per cent. The fourth is to count a banana as a rich source, when a handful of almonds holds nearly three times as much.

Safety, side effects and when to see a doctor

For a healthy adult the main unwanted effect of a supplement is loose stools, and staying at or under ICMR-NIN's limit of 350 mg a day of supplemental magnesium keeps most people clear of it. Serious excess is rare and nearly always involves laxatives or antacids in large amounts: the European committee found that the few published cases of toxic blood levels mostly followed single doses above about 2,500 mg, with low blood pressure, nausea and vomiting. It names severely impaired kidney function as a risk factor.

Do not stop a prescribed medicine, including an acid suppressant, because of something read about magnesium; raise it with the prescriber. A child's limit is far lower than an adult's, 65 mg from supplements at 1 to 3 years and 110 mg at 4 to 9 years, so adult tablets are not for children.

Learning this properly

NNWA teaches magnesium with the other minerals, under requirements, food composition and diet planning. It is a private skill academy in Kolkata that teaches online in English and Hindi; its courses train people to coach healthy clients and refer medical cases, and none is a degree or a dietitian qualification. The Diploma in Nutrition, Dietetics and Public Health covers requirements and planning, and the Clinical Nutrition course deals with diet alongside illness and medicines.