Essential Amino Acids: The Nine, the ICMR-NIN Pattern and the Indian Plate

Essential amino acids are the nine building blocks of protein that your body cannot make, so food has to supply them: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. ICMR-NIN's 2020 recommendation states each one as a share of dietary protein, from 6 mg of tryptophan to 59 mg of leucine in every gram, with lysine at 45 mg. On an Indian vegetarian plate the amino acid most likely to run short is lysine, and dal eaten with roti or rice closes that gap. This overview belongs to the proteins and amino acids section.

What are the essential amino acids, and what does essential mean?

Essential means that the body cannot build the amino acid itself, not that it matters more than the others. ICMR-NIN's Dietary Guidelines for Indians, 2024, explain that the human body requires 20 amino acids, and that nine of the 20 are not synthesised in the body and so must come from the diet. Research papers call the same nine indispensable amino acids. The remaining eleven are covered in the entry on non-essential amino acids.

Requirement tables list nine lines, but two of them are pairs. Methionine is counted with cysteine as the sulphur amino acids, and phenylalanine with tyrosine as the aromatic amino acids. Three more, leucine, isoleucine and valine, are sold together as a supplement, which the BCAA entry examines.

Each of the nine has its own page in this handbook, so this overview does not repeat them. Read about histidine, isoleucine, leucine and muscle, lysine in cereal diets, methionine, phenylalanine, threonine, tryptophan and valine in detail. How the nine are turned into a single score for a food is explained under protein quality.

How much of each essential amino acid do you need?

The need is set as a pattern: so many milligrams of each amino acid in every gram of protein you eat. ICMR-NIN's 2020 recommendation, printed in Table 8.2 of its 2024 guidelines, is shown below. It matches the adult maintenance pattern of the WHO/FAO/UNU consultation of 2007, as amended in the FAO's 2013 report on protein quality, which also gives the need by body weight.

The two requirement columns say the same thing in different units. The average adult protein requirement is 0.66 g per kg a day, and 0.66 g of protein carrying 59 mg of leucine per gram gives about 39 mg per kg. The amino acid chapter of ICMR-NIN's full 2020 report could not be opened for this entry, so the figures by body weight are the international ones, labelled as such, and no figure is quoted for pregnancy or lactation.

None of this is extra to your protein requirement; it describes what that protein should contain. ICMR-NIN's 2020 allowance is 0.83 g of protein per kg a day, 54 g for a 65 kg man and 45.7 g for a 55 kg woman, rising to 1 g per kg for people on a cereal-based diet with low-quality protein. The protein calculator gives your own number.

Do children need a different pattern from adults?

Yes. A growing child has to build new tissue as well as maintain what is there, so the need per kg is higher. In the FAO's 2013 table, protein for growth adds 0.46 g per kg a day at six months, 0.20 g at one to two years and 0.07 g from three to ten years to the 0.66 g needed for maintenance, and nothing in adults. The amino acid figures fall in step, as the table shows for three of the nine.

For judging a food or a diet, the FAO recommends three reference patterns: breast milk for infants up to six months, the six-month pattern up to three years, and the pattern of the three to ten year old for everyone older. Lysine in those three is 69, 57 and 48 mg per gram of protein. A review by Indian researchers in the British Journal of Nutrition adds that for the elderly there is not enough data to set a recommendation separate from that of adults.

Essential amino acids in Indian foods

The Indian Food Composition Tables 2017 give the amino acid profile of each food in grams per 100 g of protein; multiply by ten for mg per gram. The table shows lysine, the sulphur pair, and the amino acid that falls lowest when all nine are divided by ICMR-NIN's pattern. That last column was calculated for this entry, with no allowance for digestibility. For grams of protein, see NNWA's table of protein in Indian foods.

Every cereal is short of lysine and comfortable on the sulphur pair, every dal is the mirror image, and milk, paneer and soya bean clear the adult pattern on all nine lines. Maize has a second weak point: its protein carries 5.7 mg of tryptophan per gram against a pattern of 6, which the tryptophan entry takes up. ICMR-NIN notes that flesh foods and egg contain all the essential amino acids; the IFCT rows for egg could not be read for this entry, so no figure is given.

How does an Indian vegetarian plate cover all nine?

By putting foods that are short of different amino acids on the same plate. ICMR-NIN's 2024 guidelines advise cereals and pulses in a ratio of 3 to 1 by raw weight, and say that 250 ml of milk a day raises the intake further. Their vegetarian My Plate for the Day, with 250 g of cereals and millets, 85 g of pulses and 300 ml of milk or curd, clears the pattern on every line of the first table. Lysine has the narrowest margin, 49.0 mg against 45, and phenylalanine with tyrosine the widest, 87.9 against 38.

The same guidelines call the 3 to 1 combination the most efficient way to obtain all nine from a vegan diet, and put the digestibility of most vegetarian foods at 70 to 85 per cent. The handbook's page on the vegan diet covers the planning, the article on vegetarian protein sources lists the foods, and a plate of idli with sambar is the cereal and pulse idea in one dish.

Too little of the nine: who runs short in India?

The Indian problem is rarely too few grams of protein and more often too little of one amino acid. A review of national diet surveys in the British Journal of Nutrition found that cereals supply almost 60 per cent of the protein in Indian diets, and judged about one third of the sedentary rural population to be at risk once quality was counted. A 2018 review in the Indian Journal of Medical Research cites an analysis that put the share at risk at 4 to 26 per cent across age groups in rural and urban India, and notes that pulses, milk, egg, fish and meat together provide less than 36 per cent of protein intake.

There is no blood test or body measurement that marks a low intake of an essential amino acid, the same review says, so risk is read from diets. In young children the concern is growth. A study of Indian children found that the protein score of complementary diets in survey data fell as stunting rose, and that adding egg or milk lifted the calculated score from 80 to 100. The 2018 review warns that it is an overreach to blame protein quality alone.

What does the evidence say?

First, the adult figures are recent and rest on Indian work. The 2018 review records that the 2007 committee raised the adult pattern by two to three times, using as its primary data 24-hour tracer studies in healthy, well-nourished Indians. Leucine is its example: about 40 mg per kg a day by the new methods, against 14 mg in the 1985 report.

Second, what you absorb is less than what you eat, and the gap is wider for plants. In Indian adults, the true ileal digestibility of the essential amino acids was measured at 74.6 per cent for chickpea, 71.6 per cent for yellow pea and 63.2 per cent for whole mung bean, rising to 70.9 per cent once the mung was dehulled. The same group found 89.4 per cent for whole boiled egg and 92.0 per cent for cooked meat.

A worked example: one vegetarian day against all nine

This is an illustrative case, not a real person. Take a 30-year-old vegetarian schoolteacher in Chennai who weighs 55 kg. By the WHO figures she needs about 1,650 mg of lysine, 2,145 mg of leucine and 825 mg each of threonine and the sulphur pair a day. Suppose her grain for the day is 120 g of raw rice and 100 g of atta. From IFCT 2017 that is 20.1 g of protein carrying 607 mg of lysine, 1,417 mg of leucine and 584 mg of threonine: 37, 66 and 71 per cent of her need, though the sulphur pair, at 846 mg, is already covered.

Now add 40 g of toor dal, 30 g of moong dal and 300 ml of milk or curd, counted here as 300 g of cow's milk. Protein rises to 45.8 g, almost exactly her allowance of 45.7 g. Lysine reaches about 2,429 mg, leucine 3,623 mg, threonine 1,584 mg and the sulphur pair 1,455 mg, and every one of the nine now stands at roughly one and a half times her need or more. The sums ignore digestibility, so read them as a comparison of two days.

Common mistakes and myths about essential amino acids

The first mistake is to count grams of protein and stop. ICMR-NIN's 2024 guidelines observe that an adult's diet often provides 60 g to 70 g of protein a day, more than the requirement, and that meeting all the essential amino acids is the harder part. The second is to assume that a tub labelled EAA or BCAA does something a meal cannot; the guidelines describe protein powders as unnecessary for normal healthy life.

Supplements, safety and when to see a doctor

ICMR-NIN's 2020 table of tolerable upper limits sets none for a single amino acid; it limits protein as a share of energy, to under 40 per cent for adults. Its 2024 guidelines advise against high intakes of protein supplement powders, note recent evidence that branched chain amino acids may increase the risk of certain non-communicable diseases, and warn that high protein intakes may worsen kidney function in people who already have kidney disease. This entry gives no dose for any amino acid supplement.

See a doctor if a child is not growing along the expected curve, if you are losing weight or muscle without trying, or if your feet or face are swelling. Do not stop or change a prescribed medicine or diet because of something you have read about amino acids.

Learning about amino acids at NNWA

Proteins, amino acids and the planning of vegetarian diets are taught at NNWA, a private skill academy in Kolkata that holds its classes online in English and Hindi. Its courses, among them the Certification in Nutrition and the Diploma in Nutrition, prepare people to coach healthy clients and to refer medical cases to a doctor. None of them is a degree or a dietitian qualification.