The many myths about protein deficiency in people in India

Besides protein, milk, eggs and meat also provide vitamin B12 and choline

There are many myths about protein in India, emanating from sub-optimal understanding of nutrition biology. The first myth is that Indians are protein deficient. However, an analysis of NSS (National Sample Survey) household food intakes showed that the risk of protein deficiency (adjusted for digestible quality) in India was low in adults and non-existent at younger ages. There is another myth that protein is the critical limiting factor for physical growth in infants and children. In fact, infant growth is energy dependent: if they are fed with diverse foods to meet their energy needs, protein will be ‘carried’ along.

Biology first: since energy and protein coexist in foods, a rational and holistic way to view protein requirement is in terms of the “protein to energy ratio” (PER) in both foods and the requirement. To calculate this, protein is first converted to energy (1 gm protein=4 kcal energy), and then expressed as a ratio of the total energy to get the PER.

Examining the PER requirement is illuminating. For one-year-old-child, with protein requirement near 1 gm/kg/day, and high energy requirement of 80 kcal/kg/day, the PER of the requirement is 5%. The requirement PER rises to about 9% in active adulthood, and up to 12% in the inactive elderly. Thus, in active people, their energy requirements go up, and lowers their requirement PER. Here, eating diversely to meet the energy requirement will also carry along the required protein. The opposite occurs for older, sedentary people- their energy requirements are low, with consequently higher requirement PER, so they need to eat less, but eat higher-protein foods. In the NSS analysis, rural and urban quality-corrected PER of mixed diet intakes was 8% and 9% at all ages up to adults, which is equal to the requirement for adults and well above the 5-7% PER required for infants and children.

What foods should be eaten to meet the requirement PER? After adjusting food proteins for digestibility (breakdown into absorbable amino acids) and amino acid content, the PER of cereals is about 6% (because of low concentrations of essential amino acids like lysine), lentils 18%, milk 20%, egg 30% and lean meat 75%. Other foods like energy-dense fats (oils) and sugar, which have zero protein, have 0% PER. Therefore, a mixed diet with protein foods, but containing fats and sugar, will have a lower PER.

Therefore, in an infant, whose requirement PER is 5%, a mixed diet of cereal (6% PER) and fat/sugar (0% PER) alone will be inadequate. If supplemented with small amounts of lentil or animal protein (egg/meat), the protein content and PER will safely be higher than 5%. In older children’s diets, the PER of a cereal-dominant diet will improve with lentils, or animal foods like milk/eggs/meat; the latter also offer unique nutrients like vitamin B12 and choline. In adults, as their requirement PER increases, cereals should be progressively reduced and replaced with higher protein-plant (lentils) or animal-foods (milk/eggs/meat).

Another myth: exercise requires high protein. Muscle protein synthesis increases immediately after exercise, and protein intake is indeed required for this. But energy needs also increase, so a high-quality mixed meal is adequate to meet these immediate needs. Can ever-larger protein intakes (like whey supplements) bulk up muscle synthesis and mass ever-higher during gym training or exercise? No. Muscle protein synthesis immediately after exercise has been shown to ‘max out’ at a post-exercise protein intake of 20g in a normal adult. This is because muscle fibres are enclosed in an inelastic ‘bag’ called sarcolemma, which cannot expand infinitely. Muscle protein synthesis stops when this bag is full. The Indian ‘bag’ is also small to begin with.

Final myth: there is no risk of eating too much protein. There are risks of bone resorption and renal disease with high protein intake, but a recent careful study in Nature Metabolism gave a value for this upper limit for protein. This dose-response study showed that protein intake beyond 22% PER (25 gm/meal; a usual meal would have about 20 gm protein) negatively affected the white blood cells that were responsible for clearing up cellular debris. In humans, this is implicated in ischemic cardiovascular disease (angina, heart attack). Those authors correctly said: “…dialling up your protein intake in pursuit of better metabolic health is not a panacea.”

It is time to rationalise the claims around rampant protein deficiency in India: we certainly need good protein, but in moderation, and natural plant or animal foods have enough. Rely on farms, not pharmacies, for good health.

(Anura Kurpad is Professor of Physiology and Nutrition in St John’s Medical College, Bengaluru, and Harshpal Singh Sachdev is a senior consultant in Paediatrics and Clinical Epidemiology, Sitaram Bhartia Institute of Science and Research, New Delhi)