The Protein Myth
Modern nutrition is a twentieth-century science, and from the lofty vantage point of the early twenty-first century we can watch the early nutritionists feeling their way. The story is wonderful, full of dedication, ingenuity and insight, hacked out by scientists burning midnight oil and by doctors who often chose to live in the most difficult circumstances , in the poorest villages of Africa, Asia and South America. It is not fashionable to present the history of science as heroism, but it often has been heroic nonetheless.
Occasionally, however, the pioneers of nutritional theory went astray. In the 1930s, and for a few decades afterwards, they seemed to misconstrue the problem. The mistake was made for commendable reasons, and the analysis was not grossly inaccurate. Yet it led to a huge and potentially extremely damaging perversion of food policy.
Proteins are the body’s executives and general functionaries. They form much of the stuff of flesh. They also provide the raw materials for a large number of hormones; haemoglobin, which carries oxygen in the blood; antibodies, which are the body’s defence against infection; and enzymes, which are biological catalysts, which conduct the whole metabolism.
Chemically speaking, proteins are compounded from carbon, hydrogen, oxygen and nitrogen, with a small but highly significant content of sulphur (highly significant because the position of the sulphur atoms largely determines the overall shape of the protein molecule; and its qualities depend on its overall shape). More specifically, proteins are compounded from chains of amino acids.
Twenty-something amino acids are known in nature, of which about twenty are found in the human body. About a dozen of these latter are conventionally said to be ‘non-essential’, which does not mean that the body does not need them. It simply means that they do not need to be present in the food, because the body is able to make these ‘non-essential’ types from other amino acids that are present. But eight are said to be ‘essential’ because the body cannot manufacture them from other amino acids. These have to be present in food.
Ideally, dietary proteins should contain all the essential amino acids, in the ratios in which the body requires them. If any one essential amino acid is present in less than the ideal quantity, then the quality and the dietary value of the whole protein are compromised. The essential amino acid that is least well represented becomes the ‘limiting factor’, dragging down the quality of the whole. Animal proteins in general (not always, but usually) contain all the essential amino acids that humans require, in ideal quantities — as they seem more or less bound to, since animal flesh is very like ours. But plant proteins are often (relatively) deficient in one or more essential amino acids. Notably, cereal proteins tend to be low in the amino acid known as lysine; and pulse proteins, as in beans, tend to be low in tryptophan. Traditionally, then, nutritionists have declared that animal proteins are ‘first-class’; whereas most plant proteins have been dubbed ‘second-class’.
In the 1930s the belief developed that people in general need a massive intake of protein, and that this protein had to be of the very highest quality. In other words, the belief developed that people need to eat animal protein. By the early 1960s, when I first started taking a serious interest in nutrition, it was commonly argued in effect that the more animal protein we ate, the better. (The dangers of animal fat, which are always liable to accompany animal protein, had not yet become fully apparent). Correspondingly, nutritionists of the mid twentieth century tended to argue that plant proteins, with the possible exception of soya, were inadequate both in quantity and in quality. By the early 1960s potatoes, and even cereals, were virtually being written off as ‘empty starch’ – at least in popular articles, of the kind on which people at large typically rely.
For various reasons, this emphasis on protein in general, and on animal protein in particular, was pernicious. Yet as Professor Donald S. McLaren, then at the American University of Beirut, outlined in the mid 1970s (‘The Great Protein Fiasco’, The Lancet, 1974, vol. 2, p. 93), this huge and damaging mistake arose from fine observations that were made for the most humane reasons — but with a measure of bad luck thrown in. For McLaren pointed out that malnutrition was widely studied in the 1920s and 30s, and that it presented a confusing picture. It can manifest in many forms. Poor diets may make people thin (although thinness may also be normal and at times of course may simply be fashionable). Or malnutrition can make people sluggish (although sluggishness too can have a hundred other causes, ranging from infection to temperament). Or it can lead to a vague puffiness, or an increased susceptibility to infection.
All in all, it can be extraordinarily difficult to tell, when faced with a thin, sick child, whether he or she is thin for purely genetic reasons (what used to be called an ‘ectomorphic’ body type), or is wasted by infection, or whether the infection and the thinness are both rooted in poor diet — and if so, where the dietary deficiency lies.
Serious light began to dawn in 1932. Dr Cicely Williams, who was the first woman medical officer in Africa’s Gold Coast (now Ghana) described a ‘deficiency disease of infants’ in which, she said, ‘some amino acids or protein deficiency cannot be excluded’. This, of course, is a supremely guarded statement, as preliminary observations in science should always be. It makes no claims; it merely raises possibilities that should be looked at. The deficiency disease in question was kwashior-kor, a well-recognized syndrome in which the hair and skin are dry, the hair is reddened, and the belly is swollen not by obesity but by oedema. Biochemists later demonstrated distinct alterations in blood chemistry, which gave laboratory support to the more subjective clinical findings.
Kwashiorkor was distressingly common in Africa throughout the twen-tieth century; and although the precise mechanism remains uncertain, lack of protein is definitely implicated. Dr Williams’ observation was a great advance. But fate took over. As Professor McLaren recalls, ‘During the late 1930s and 1940s, when international meetings were virtually non-existent and travel was limited, discussion of the nature of malnutrition in children was carried on through the correspondence columns of journals.’ Significantly, this correspondence was ‘mainly between workers in different parts of Africa’, where many people rely upon cassava. Cassava, a starchy root, just happens to be the only one of the world’s major staples that really is deficient in protein.
The Second World War interrupted further research. When the war was finally over, the newly created World Health Organization and the Food and Agricultural Organization of the United Nations were anxious, in a new and optimistic world, to get on with the task of feeding the world’s hungry. They built on pre-war observations, which were all that was available. In 1953, in an influential report entitled Kwashiorkor in Africa, they made the much-quoted statement that kwashiorkor was ‘the most serious and widespread nutritional disorder known to medical and nutritional science’. Yet, says McLaren, this statement was made ‘without reference to the rest of the world and other forms of malnutrition’. The die was cast, however. Kwashiorkor was perceived to be the greatest problem; and the single greatest cause was deficiency of protein.
The general idea of protein deficiency was in the air at the time that Cicely Williams first wrote about it. John Steinbeck seemed to have just such a notion in mind when he wrote his first major novel, Tortilla Flat, published in 1935. Steinbeck tells us it is ‘the story of Danny and of Danny’s friends and of Danny’s house’, and is set near Monterey, ‘that old city on the coast of California’. Danny is a paisano, meaning he has ‘a mixture of Spanish, Indian, Mexican and assorted Caucasian bloods. His ancestors have lived in California for one or two hundred years’.
One of Danny’s friends is Teresina, who has an extraordinary number of children, among whom is Alfredo. And:
At about this time in California it became the stylish thing for school nurses to visit the classes and to catechize the children on intimate details of their home life. In the first grade, Alfredo was called to the principal’s office, for it was thought that he looked thin.
The visiting nurse, trained in child psychology, said kindly: ‘Freddie, do you get enough to eat?’
‘Sure’, said Alfredo.
‘Well, now. Tell me what you have had for breakfast.’
‘Tortillas and beans’, said Alfredo.
‘[Do] you eat at noon?’
‘Sure. I bring some beans wrapped up in a tortilla.’
Actual alarm showed in the nurse’s eyes, but she controlled herself. ‘At night, what do you have to eat?’
‘Tortillas and beans.’
Her psychology deserted her. ‘Do you mean to stand there and tell me you eat nothing but tortillas and beans?’
Alfredo was astonished. ‘Jesus Christ’, he said, ‘what more do you want?’
Perhaps the school nurse was alarmed by the lack of fruit and vegetables; but meat and milk were surely uppermost in her mind. At that time, few seriously believed that people and especially children could do without them. Twenty years later, by the 1950s, this supposition had become official theory. The production of protein, in the form of meat and dairy products, became a mission and then, almost indistinguishably, a bandwagon. The US, with all its cash, space, grass and surplus cereals, was perfectly positioned to oblige the world at large. As always, it was generous; and as always, the boundaries between altruism and self-interest were blurred. Crudely speaking, the US unloaded its dairy surpluses on to Third World countries; and when those surpluses dried up, as they had by 1964, they were replaced by what McLaren called ‘protein-rich food mixtures’, the manufacture and distribution of which were widely acknowledged as necessary succour for people in poor countries. To be sure, malnutrition was still widespread.
Yet it continues to astonish me that so few people in high places seemed to ask how it was that the populations of Africa and Asia had thrived for so many thousands of years before the Western world opted to shower them with food supplements. In The Hungry Planet (Macmillan, London, 1967) and later in Too Many (Macmillan, London, 1969) the geographer Professor Georg Borgstrom of Michigan State University argued that a large proportion of the human race must already be doomed since they clearly did not have enough protein, which mainly meant meat. Yet if the people of Africa and Asia had really been so deficient in their traditional diets, they would not be here at all.
But some scientists, including Professor McLaren, doubted even from the early 19505 whether the emphasis on protein and more protein was really appropriate. As the 19705 progressed, it became clear that it was not. The Indian nutritionist P. V. Sukhatme was prominent among those who stressed the concept of ‘protein sparing’ (see for example British Journal of Nutrition, 1970, vol. 24, pp. 477–87; and J. C. Waterlow and P. R. Payne, ‘The protein gap’, Nature, 1975, vol. 2.58, pp. 113–17). Professor Sukhatme found that malnourished, ostensibly protein-deficient children in India improved not only when given protein-rich foods, but also when given more ‘ordinary’ local foods, such as cereal and beans. Of course, cereals and beans do not simply provide energy, as sugar does. They are also sources of protein. But they are not officiously ‘high-protein’ foods of the kind that had been considered necessary.
So it turned out that malnourished children, even those with kwashior-kor, were not usually short of protein in particular, but of food in general. More specifically, the body needs both energy, to keep it going, and protein, from which to construct and reconstruct its own fabric. But, as outlined above, the body has its priorities. If it is short of energy it will first of all metabolize glycogen in the muscles and liver; and as that runs low, it mobilizes its stores of fat. But if it is still short of energy after that, then it burns protein. If you give protein to children who do not have enough energy foods, then their bodies burn the protein. Then they suffer protein deficiency and they may (although not necessarily) begin to show the specific signs of kwashiorkor. Conversely, high-energy foods will ‘spare’ the body protein and even a modest intake will be seen to be adequate.
In general, protein nutrition has two separate aspects. First, the body must receive a basic, absolute quantity of protein that ideally should be eaten every day, because surpluses of protein (unlike surpluses of sugar and fat) are not stored. On any day that the body misses out on protein, it has to draw upon body tissue, notably muscle, to make good the shortfall. The immune system, which is heavily protein-dependent (antibodies are protein) is presumably compromised as well.
Proportion matters, too — the ratio of protein ingested relative to the total energy. If the body receives too little energy, then it will burn some of its protein to make good the shortfall, so even if it takes in an amount that should be adequate, it will still experience deficiency. On the other hand, if the body is plied with sufficient protein and also with excess energy, then it will put on fat. Hence a person could get enough protein (in absolute terms) even by eating a low-protein food such as cassava, but in doing so he or she would take so much surplus energy on board that their bodies would soon become spherical.
But thanks to scientists like McLaren, Sukhatme and others, official nutritional authorities reduced recommended intakes of protein about threefold between the late 1940s and the mid 1970s; and recommen-dations remain at the more modest level. Thus in 1948 the National Research Council of America (NRCA) recommended that children aged one year should receive 3.3 grams of protein per kilogram of body weight per day. In ~ the FAO had brought this down to 2.0 grams per kilogram for one-year-olds, and by 1971 made a further, even more dramatic reduction, to 1.2 grams per kilogram. Adults, metabolizing more slowly and no longer piling on muscle, require only half as much protein per unit of body weight as children do.
But, during all that time, the recommended energy intake remained steady (as it has ever since). After all, energy requirements are easier to calculate, and to get right. Thus the NRCA recommended 100 calories per kilogram body weight for one-year-olds in 1948, while in 1971 the FAO were recommending 105 calories per kilogram.
Since recommended protein has gone down (dramatically) while rec-ommended energy has remained steady, the ratio of protein to energy that human beings are thought to need has also dropped. According to the 1948 figures, a child would need to obtain i~ per cent of his or her total diet in the form of protein. According to the 1971 (and present-day) figures, 5 to 6.5 per cent is adequate; and for adults, at least when they are not pregnant or lactating, about 3 per cent is enough.
This change of mind has profound implications. Even when you make suitable adjustments for the quality of protein, all the world’s great staple crops, including wheat, rice, millet and even potatoes, emerge as perfectly adequate sources of protein. If you eat enough of any of them to satisfy your daily energy requirements (which, after all, is what staples are supposed to do) then you will automatically satisfy your protein requirements as well. You do not need to eat excessive amounts of those staples, which would make you fat; or to supplement them with protein-rich supplements — of which meat is the prime exemplar.
To be sure, an exclusive diet of wheat or rice would lead to serious deficiencies of vitamins and minerals (although an heroic Danish physiologist did once contrive to live for a year on an exclusive diet of potatoes; and people in parts of Western Europe through much of the nineteenth century also subsisted virtually entirely on potatoes, as depicted not least by Vincent Van Gogh). Nonetheless, a diet adequate in staples should not be deficient either in energy or in protein; and once these ‘macronutrients’ are taken care of, the rest should be relatively easy.
Even the issue of protein quality is easily resolved. Traditionally the proteins from cereals were called ‘second-class’ because they contain relatively low quantities of some of the essential amino acids, notably lysine. However, once the overall requirement for protein is seen to be fairly modest, then the shortfall in quality ceases to matter. There is not as much lysine in cereal protein as is ideal, but there is enough nonetheless. Besides, nature has laid on a wonderful serendipity. The proteins of pulses — beans, peas, lentils — are relatively rich in lysine. So when cereals and pulses are eaten together, their combined proteins have an excellent spectrum of amino acids: together, they become ‘first-class’.
We find (should it be a surprise?) that cereal — pulse combinations are prominent in all the world’s great traditional cuisines. The Indians eat chapattis or rice with chickpeas or dhal, made from a variety of beans and lentils. The Chinese and Japanese traditionally eat bean curd (tofu) with rice. Rice and peas is a staple of the West Indies. The English are not great pulse eaters (apart from mushy peas) but even they eat baked beans on toast (although the beans are generally American). The Mexicans, of course, eat tortillas (made from maize) with frijoles (beans). If Steinbeck’s nurse had known what became apparent forty years later, Alfredo’s diet would not have bothered her at all (give or take a few vitamins). As Alfredo put it himself, ‘What more do you want?’
But in the days of the protein myth, roughly from the 1930s through to the 1970s, nutritionists were in effect telling humanity that we could not survive, or at least live to our full potential, unless we had access to high-protein foods, which in particular meant meat. Farmers were very happy to oblige. Commercially this was very good for them.
This over-emphasis on meat, made respectable first by nutritionists and then by sociologists, has been the most pernicious of all trends in modern agriculture: damaging to humanity in many different ways — nutritional, economic, cultural; damaging to the beleaguered beasts who have supplied the feast; and very damaging indeed to the earth as a whole, and to the future prospects of all the creatures, including us, who live on it.
This article is an extract from Colin Tudge’s book So Shall We Reap: How Everyone Who Is Liable to Be Born in the Next Ten Thousand Years Could Eat Very Well Indeed; and Why, in Practice, Our Immediate Descendants Are Likely to Be in Serious Trouble.
One of the most important books of it’s time, it’s essential reading for anyone who needs food and/or cares about the future.
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