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Protein quality: why the grams are not the whole story

Two meals can have the same grams of protein, and your body may use different amounts of each. India's dietary guidelines explain why cereal protein runs short of lysine, and how pulses, milk and cooking help.

KiloCare Team · · How we write and review

On Sunday the rotis come to the table in a tall stack, and the dal in one small katori.

Does the protein still add up when the katori of dal is small next to the rotis? A food table can say a meal holds 20 g of protein. It cannot say how much of that your body gets to use. That depends on the quality of the protein.

What "quality" means

Protein is built from amino acids. The body cannot make 9 of them, so they must come from food.[1]

Quality has 2 parts. One is whether a food supplies all 9 in the right proportions. The other is how well the protein is digested and absorbed. India's dietary guidelines say animal proteins give all 9 in the right proportions and are more easily digested. Plant proteins are low in some of the 9.[1]

The Food and Agriculture Organization (FAO) of the United Nations scores a protein by the amino acid it is shortest of, after allowing for digestion. For each of the 9, the score compares the digestible amount in 1 g of the protein with a reference amount. The lowest of the 9 ratios becomes the score.[2]

Lysine and methionine

NIN, the ICMR-National Institute of Nutrition, says cereals have less lysine and more methionine. Pulses are the other way round.[1]

A meal with both a cereal and a pulse supplies all the amino acids. NIN says it is of higher quality than a diet of pulses alone or grains alone.[1]

Where Indian protein comes from

In the 2022-23 household survey, cereals were the largest of the 5 food groups for protein. They supplied 46.9% of protein intake in rural India and 38.8% in urban India.[5]

Pulses supplied 8.8% and 9.6%.[5]

A 2018 review by Indian researchers describes cereal protein as relatively low in quality, with lysine as the limiting amino acid.[4]

How well it is digested

The same review reports how much of the protein's amino acids a body absorbs. In children aged 1.5 to 2 years, the average was 79% for rice, 68% for finger millet, 65% for mung bean and 87% for a boiled egg.[4] These are measurements in toddlers, so they are not figures for an adult's plate.

NIN says most vegetarian foods have a protein digestibility of 70% to 85%.[1] A balanced vegan diet for a moderately active man gives more than 80 g of crude protein a day. NIN puts that at about 60 g of quality protein, enough for all 9 amino acids.[1]

The total on the label and the amount your body can use are different numbers.

What lower quality changes

NIN's allowance of 0.83 g per kg a day assumes good-quality protein. For people eating a mostly cereal diet with low-quality protein, NIN gives 1 g per kg a day.[3]

For a 65 kg adult, that is 65 g a day instead of 54 g.

The Indian review estimated what share of people could fall short once quality is counted, using lysine. For different age groups in rural and urban India, it put the share at risk of quality-protein inadequacy at 4% to 26%. That assumes good health and a clean environment. It is a modelled estimate, not a count of people who are deficient.[4]

The same review lists links between low-lysine diets and lower levels of some immune markers. It also says poor protein quality may be associated with childhood stunting, and calls it an overreach to blame protein quality alone. It adds that populations eating poor-quality cereal protein have survived quite effectively.[4] These are findings about populations. They do not show that one meal does harm.

For muscle, a 2019 review found that in studies of a single meal, plant protein gave less muscle protein synthesis than animal protein. It links this to lower digestibility, less leucine and limiting amino acids.[6] It reports that a larger dose, or a blend of plant and animal protein, narrowed the gap in some studies, with mixed results in older adults.[6] To the authors' knowledge, a cereal and legume blend had not been studied in older adults.[6]

NIN adds that without enough physical activity or resistance exercise, protein will not be used to build muscle.[1]

What helps

NIN suggests about 3 parts cereal to 1 part pulse by raw weight. It says this mix can meet the need for all the essential amino acids, and that 250 ml of milk a day adds more.[1]

Boiling or pressure-cooking pulses destroys anti-nutritional factors, which makes their protein easier to digest. Cooking them far too long loses some lysine.[1]

Anyone who takes medicine for diabetes should check with their doctor before changing how much rice or roti they eat.

If you have kidney disease or have been told to limit protein, ask your doctor how much protein is right for you.

Check your own day

Use this list to check the protein quality of what you ate today.

Protein quality in my day

This Sunday the katori is a little bigger, and it goes round the table twice.

Quality is how well a food's protein matches what the body needs. It depends on whether the food has all 9 essential amino acids in the right proportions, and how well the protein is digested and absorbed. India's dietary guidelines say animal proteins give all 9 in the right proportions, while plant proteins are low in some.

Cereals are low in an essential amino acid called lysine, and pulses are low in methionine. India's dietary guidelines say a meal with both a cereal and a pulse supplies all the essential amino acids and is of higher quality than either alone. For a diet that is mostly cereal, the national allowance is 1 g per kg of body weight a day instead of 0.83 g.

India's dietary guidelines suggest about 3 parts cereal to 1 part pulse by raw weight, and about 250 ml of milk a day. They also say boiling or pressure-cooking pulses makes their protein easier to digest, and cooking them for too long loses some lysine. If you have kidney disease or have been told to limit protein, ask your doctor how much protein is right for you.

Sources

  1. ICMR-NIN Expert Committee. Dietary Guidelines for Indians - 2024. Hyderabad: ICMR-National Institute of Nutrition; 2024. Available from: nin.res.inCited atp. 9, Guideline 1p. 9, Guideline 1; p. 60, Table 8.2p. 58p. 58, Table 8.1p. 59p. 59p. 59p. 58p. 83
  2. Food and Agriculture Organization of the United Nations. Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. Rome: FAO; 2013. FAO Food and Nutrition Paper 92. Available from: fao.orgCited atp. 3, §2.1; p. 21, §4.1
  3. ICMR-National Institute of Nutrition. A brief note on nutrient requirements for Indians, the recommended dietary allowances (RDA) and the estimated average requirements (EAR). Hyderabad: ICMR-NIN; 2020. Available from: nin.res.inCited atp. 5, Table 2a
  4. Shivakumar N, Minocha S, Kurpad AV. Protein quality & amino acid requirements in relation to needs in India. Indian J Med Res. 2018;148(5):557-68. Available from: ijmr.org.inCited atImplicationsTrue ileal digestibility in humansEconomic and policy implications for IndiaImplications
  5. Ministry of Statistics and Programme Implementation. Household Consumption Expenditure Survey: 2022-23 & 2023-24: Nutritional Intake in India [press release]. New Delhi: National Statistics Office; 2025 Jul 2. Available from: mospi.gov.inCited atFigures 4R and 4U, pp. 4-5Figures 4R and 4U, pp. 4-5
  6. Berrazaga I, Micard V, Gueugneau M, Walrand S. The role of the anabolic properties of plant- versus animal-based protein sources in supporting muscle mass maintenance: a critical review. Nutrients. 2019;11(8):1825. doi:10.3390/nu11081825. Available from: pmc.ncbi.nlm.nih.govCited atAbstractSections 4.1 and 4.3.2Section 4.3.1