The protein gap – nutritional science’s biggest error
In the three decades following World War II it became an almost universal belief of nutritional scientists that protein deficiency was the most serious and widespread dietary deficiency in the world. Improving protein nutrition became a high priority for UN agencies, such as the Food and Agriculture Organisation.
This problem was perceived to be so serious and widespread that in many developing countries most children were thought to suffer some degree of protein malnutrition – a condition the medical establishment called “kwashiorkor”. (Kwashiorkor is a word from the Ga language of West Africa that means “the disease of the deposed child”.)
For several decades, protein was a major teaching and research focus in human nutrition. This focus on protein and protein deficiency has persisted in many minds, even though official recommended daily allowances (RDA) suggest that deficiency is very unlikely. Some foods, including eggs, milk (especially skimmed milk) mushrooms, lentils and Quorn are still prized and afforded “superfood” status as rich sources of high-quality protein.
As late as 1972, Hugues Gounelle de Pontanel, later the president of the French National Academy of Medicine, made the following claim in his opening address at a scientific conference on the generation of protein from oil in France:
Every doctor, nutritionist or political leader concerned with the problem of world hunger has now concluded that the major problem is one of protein malnutrition.
When estimates of world protein needs were made using official estimates of protein requirements, there appeared to be a huge and rapidly increasing shortfall in supplies that was termed the “protein gap”. The low quality of many vegetable proteins and uneven worldwide distribution of protein amplified the problem. The protein gap seemed unbridgeable unless alternative – and previously untapped – sources of high-quality protein could be found.
Billions of pounds at today’s prices were invested in measures to try and close this protein gap. Some of the efforts included:
• Developing high-protein strains of cereals or adding synthetic amino acids (the building blocks of proteins) to increase the quality of wheat protein.
• Making so-called single-cell protein from micro-organisms (Quorn is one such product produced from a microscopic fungus and now marketed as a meat substitute for vegetarians).
• Mass producing palatable high-protein foods from products such as cotton seeds, sesame seeds, fish meal and soya beans.
The Protein Advisory Group, a UN agency, was established in 1955 to advise on the “safety and suitability” of these new protein-rich foods.
An emperor’s new clothes moment
However, the protein gap was finally exposed as a myth in 1974 when Donald McLaren, of the American University in Beirut, published a paper in The Lancet titled: “The great protein fiasco”. In a 2011 interview, reflecting on his life and career, McLaren described the belief in the protein gap as “one of the greatest errors committed in the name of nutrition science in the past half-century”.
A year after McLaren’s paper appeared in The Lancet, John Waterlow and Philip Payne from the London School of Hygiene and Tropical Medicine published an analysis of diets of children in developing countries. Their analysis revealed that protein deficiency was rare, and when it occurred it was caused by a simple lack of food, rather than the low-protein content of food. Even diets based on low-protein staples, such as yams and cassava, contain enough protein for human needs. Waterlow and Payne concluded that neither the protein-gap theory nor the diagnosis of kwashiorkor as a disease caused by protein deficiency remained tenable. It is still unclear why some malnourished children develop kwashiorkor.
Three major factors led to the false belief in a world protein crisis: exaggerated official estimates of human protein requirements, especially those of growing children; overemphasis of the importance of the protein quality of individual foods; and the assumption that kwashiorkor was caused by protein deficiency and was the most common worldwide manifestation of malnutrition in children.
In 1943, the US RDA for protein for a two-year-old child was 40g a day. It is now only 18g a day. Using the 1943 RDA, protein deficiency would have seemed almost inevitable for children in many developing countries and a distinct possibility even in developed countries. The adult male RDA has fallen from 65g a day in 1943 to 55.5g a day now.
Back in 1959, Dr Mark Hegsted of the Harvard School of Public Health warned that estimated human protein requirements were excessively reliant on animal studies. Rats double their birth weight in four to six days and baby rats need five times more protein than adults when allowance is made for size differences. Breastfed human babies may take four to six months to double their birth weight, so their extra protein needs for growth are much more modest than those of a baby rat. Rat milk also has seven times as much protein as breastmilk, so animal comparisons tended to exaggerate the extra protein needs of a growing child.
Despite the fact that the protein gap theory has been thoroughly debunked, the focus on protein deficiency still persists in many minds. As recently as 2015, the Times of India ran an article with the headline: “Nine out of ten Indians lack proper protein intake”.
Sometimes bad ideas simply refuse to die.