Calcium: ICMR-NIN Requirement by Age, Absorption, Indian Intake and the Kidney Stone Question

Calcium is the mineral that makes bones and teeth hard. ICMR-NIN's Nutrient Requirements for Indians 2020 sets the recommended allowance at 1,000 mg a day for adult men and women, up from 600 mg in the 2010 edition, and at 1,200 mg during lactation, after menopause and from the age of 60. The tolerable upper limit for adults is 2,500 mg. This entry in the minerals section of the handbook covers the values for every age, absorption, the Indian intake figures and the evidence on supplements.

What does calcium do in the body?

Most of what calcium does, it does in the skeleton. A 2017 systematic review for the International Osteoporosis Foundation describes calcium as accounting for about 30 to 35 per cent of the mass of bone and much of its strength. The same review notes that bone is lost at about 1 per cent a year late in life, which is why adolescence and old age dominate every discussion of this mineral.

ICMR-NIN's expert group gives the same reasoning for its own figures. Reaching peak bone density is, in its words, essential to prevent osteoporotic fractures in later life, and the rate at which bone is laid down during puberty decides body size and skeletal maturity. The 2024 Dietary Guidelines for Indians add that calcium and vitamin D in pregnancy and lactation are needed for the baby's bones and teeth, for breast milk, and to protect the mother from osteoporosis.

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

An adult needs 1,000 mg a day on the recommended allowance, and 800 mg on the estimated average requirement that planners use to judge a population's diet. The expert group raised both because the 2010 figure rested on a zero-balance point for men, 334 mg, that was much lower than other countries used. It kept the adult value for pregnancy, on the ground that calcium absorption roughly doubles then, and raised it to 1,200 mg for lactation and after menopause, when absorption is poorer.

One row needs a note. For 16 to 18 years the report's summary annexures print 1,050 and 850 mg, the figures used here, while the calcium table in its text prints 1,000 and 800 mg; the 2024 guidelines speak of 850 to 1,050 mg for adolescents. The same report sets phosphorus on a molar ratio of 1 to 1 with calcium, which the phosphorus entry explains. The upper limit counts habitual intake from food, fortified products and tablets together.

Indian food sources of calcium, portion by portion

Milk and what is made from it, ragi, sesame and some green leaves carry most of the calcium in Indian food; rice and wheat carry very little. The table turns the per 100 g values of the Indian Food Composition Tables 2017 into household portions, raw weights for grains and pulses. The ranked figures are in the calcium table of Indian foods, and the article on calcium-rich Indian foods beyond milk goes through the food groups and the kitchen habits.

Two points follow from the table. First, the cereal matters: 60 g of finger millet (ragi) gives more than ten times the calcium of the same weight of atta, so a ragi roti, ragi mudde or a ragi dosa changes the day's total in a way that rice cannot. Second, fish flesh is a modest source. The Indian tables give 39 mg per 100 g for rohu and 159 mg for Bombay duck, measured on the edible portion; small fish eaten whole with their bones are a different matter, but the tables do not give a figure for them.

How much of the calcium in food do you absorb?

Less than the label suggests, and the share depends on the food. In a crossover study in 13 healthy adults, each test meal carried 200 mg of labelled calcium: absorption averaged 27.6 per cent from milk and 5.1 per cent from spinach. The reason is oxalate, an organic acid that binds calcium in the gut. The Indian tables measure it: spinach has 592 mg of total oxalate per 100 g and amaranth leaves 779 mg, against 120 mg in drumstick leaves and 34 mg in fenugreek leaves.

Sesame deserves the same honesty. Black sesame carries 1,664 mg of calcium per 100 g in the Indian tables and also 2,156 mg of total oxalate, the highest oxalate figure among the foods listed here, so the spoonful in the table will not all be absorbed. No Indian absorption study of sesame was found for this entry, so no percentage is given. The page on sesame seeds has the full panel.

Vitamin D is the partner that matters most, and the handbook treats it in its own entry on vitamin D. The 2019 national survey of children, as tabulated in the 2024 guidelines, found low 25-hydroxy vitamin D in 13.7 per cent of children aged 1 to 4, 18.2 per cent at 5 to 9 and 23.9 per cent at 10 to 19. See also vitamin D deficiency in India.

Calcium intake in India: the survey figures

Indian adults eat less than half the allowance. The 2017 review of national dietary surveys found average intakes from 175 to 1,233 mg a day across 74 countries; its figure for India, from 2011-12 survey data on 306,329 adults, was 429 mg a day, with women at 0.83 of the men's intake. The Ministry of Health and Family Welfare's 2014 guideline cites National Nutrition Monitoring Bureau data from 10 states showing pregnant and lactating women at less than 30 per cent of the allowance then in force.

Milk is the obvious gap. In the National Family Health Survey of 2019-21, 49 per cent of women aged 15 to 49 had milk or curd daily, 24 per cent weekly, 22 per cent only occasionally and 6 per cent never. Weekly consumption ranged from 30 per cent of women in Odisha to 94 per cent in Karnataka.

What does India's health programme give in pregnancy?

The Ministry's National Guidelines for Calcium Supplementation During Pregnancy and Lactation, issued in December 2014, provide two tablets a day, each with 500 mg of elemental calcium and 250 IU of vitamin D3, from 14 weeks of pregnancy until six months after delivery. That is the programme's schedule, reported here as such and not as advice to buy tablets. The guideline says to take one tablet with each of two meals, not on an empty stomach, and to keep it apart from the iron and folic acid tablet, because calcium inhibits iron absorption. The pregnancy diet guide sets this within the whole diet.

Do calcium supplements prevent fractures?

The trial evidence says the effect is small. A 2015 meta-analysis of 59 randomised trials in people over 50 found that raising calcium intake, from food or from tablets, increased bone mineral density by 0.6 to 1.8 per cent over one to two years, with no further gain after that. Its companion review of fracture found that supplements lowered total fractures in pooled trials (relative risk 0.89), but not in the four trials at lowest risk of bias, and called the evidence weak and inconsistent.

The largest single trial points the same way. The Women's Health Initiative gave 36,282 postmenopausal women 1,000 mg of calcium with 400 IU of vitamin D3, or placebo, for an average of seven years. Hip bone density was 1.06 per cent higher on the supplement, but the fall in hip fracture was not statistically significant (hazard ratio 0.88, confidence interval 0.72 to 1.08). Diet after menopause is covered in the menopause diet guide.

Do calcium tablets cause kidney stones?

Tablets raise the risk a little; calcium in food appears to lower it. In the Women's Health Initiative, kidney stones were 17 per cent more frequent on the supplement (hazard ratio 1.17). In a 12-year study of 91,731 nurses, women with the highest dietary calcium had fewer stones than those with the lowest (relative risk 0.65), while supplement users had more (1.20). The authors' explanation was that calcium eaten with a meal binds oxalate in the gut, and that two thirds of supplement users took the tablet without food or with a meal low in oxalate.

A five-year Italian trial tested the idea in 120 men with recurrent calcium oxalate stones. On a diet with a normal amount of calcium and less animal protein and salt, 12 of 60 men had a relapse; on the traditional low-calcium diet, 23 of 60 did. That is one trial in men with a specific condition, so the decision for any one patient is the doctor's. The kidney stone diet chart covers the food side.

A worked example: one vegetarian day against 1,000 mg

This is an illustration with an invented person, not a case record. Take a 32-year-old vegetarian school teacher in Pune. Her day holds one glass of milk across her tea and breakfast (200 g, 236 mg of calcium), four chapatis (120 g atta, 37 mg), rice (75 g raw, 6 mg), masoor dal (30 g, 13 mg), rajma (30 g, 38 mg) and a palak sabzi (100 g, 82 mg). The total is about 412 mg: close to the Indian average, about half the average requirement of 800 mg, and the spinach share is poorly absorbed.

Three changes close the gap on paper. Two ragi rotis in place of two of the chapatis add about 200 mg. A 50 g piece of paneer adds 238 mg. Methi leaves in place of spinach add 192 mg and bring less oxalate. The day now stands near 1,042 mg without a tablet.

Common mistakes with calcium

A quieter mistake is to read the allowance as a target for a tablet. The 1,000 mg is a total from everything you eat and drink, so someone already getting 600 mg from food is short by 400 mg, not by 1,000 mg. The pooled trials found similar bone density gains at doses below and above 1,000 mg a day.

Too much calcium, side effects and when to see a doctor

ICMR-NIN's upper limit is 2,500 mg a day for adults, including pregnant and lactating women, 3,000 mg from 10 to 18 years, 2,500 mg from 4 to 9 years and 1,500 mg from 1 to 3 years. Food alone rarely approaches these figures; tablets and fortified products are how people exceed them. The harm best documented in trials is the kidney stone risk described above. People with kidney disease or a history of stones, and anyone on long-term medicines, should not start a calcium supplement without their doctor's advice. The chronic kidney disease diet guide explains why the advice changes there.

See a doctor, and do not self-treat, for a fracture after a minor fall, loss of height, persistent bone pain, muscle cramps or tingling that keeps returning, or a child whose legs are bowing or who is slow to walk. Bone density scans and blood calcium, vitamin D and parathyroid tests are read together by the doctor; a single figure on a report does not tell you how much calcium to take.

Learning this properly

Calcium is taught in NNWA's courses under mineral requirements, life-stage nutrition and bone health. NNWA is a private skill academy in Kolkata teaching 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 requirements and diet planning, and the Clinical Nutrition course looks at diet around conditions such as kidney stones.