A Brief History of Protein
Passion, Social Bigotry, Rats, and Enlightenment
by John McDougall M.D.
Nutrition is an emotional subject and nothing arouses people’s passions more than the subject of protein in their diet. Widely divergent opinions on whether more protein or less is best, and on the merits of animal vs. vegetable sources, have been debated for more than 150 years. And for all that time solid scientific research has clearly supported the wisdom of a diet low in protein – favoring vegetable sources. So far, however, the scientific facts have fought a losing battle against popular opinion – which values high-protein diets based on animal foods. Mark Twain once said, “Truth is mighty and will prevail. There is nothing wrong with this, except that it ain't so.” Even though the facts may never become popular knowledge, I will always believe it is your fundamental right to know the truth about your nutritional requirements – this vital information should be taught from childhood as basic education, along with reading, writing, and mathematics – and along with health facts such as cigarettes cause lung damage, drunk driving kills, and automobile safety belts save lives.
High Protein Standard Set by Social Bigotry
One of the earliest proponents of high protein diets was the distinguished German physiologist Dr. Carl Voit (1831-1908).1,2 After studying laborers who consumed approximately 3100 Calories daily, he concluded that protein intake for people should be 118 grams (g) per day – this value became known as the “Voit standard.” How did he reach this conclusion? He believed that people with sufficient income to afford almost any choice of foods – from meat to vegetables – would instinctively select a diet containing the right amount of protein to maintain health and productivity. Other European and American authorities made similar observations about the eating habits of working men with sufficient incomes to afford meat and came to similar conclusions – ultimately recommending diets high in protein (100 and 189 grams of protein a day). No experiments were performed on the human body to reach these conclusions. Information on the diets of vigorous individuals living during these times and following low-protein vegetarian diets was largely ignored.2,3 The healthy active lives of hundreds of millions of less affluent people laboring in Asia, Africa, and Central and South America on diets with less than half the amount of protein recommended by Dr. Voit (and almost no meat), were overlooked when experts established protein requirements that still affect us today.3,4
What arrogance! To conclude that the superior intellect of moderately affluent people of European descent would cause them to naturally come to correct conclusions about their personal nutritional needs. What foolishness! You can see the effects of self-selection when unrestricted food choices are available. What do more than one billion people living in the 21st century choose? McDonald’s, Burger King, Pizza Hut – need more be said about people’s innate wisdom to make food selections in their best interests? Unfortunately, these flawed recommendations based upon such social bigotry have not yet been silenced by over 100 years of scientific research.
Russell Henry Chittenden Tells the Truth a Century Ago
Such narrow-minded thinking should have been stopped by 1905 when Russell Henry Chittenden, Yale University Professor of Physiological Chemistry, published his scientific findings on human protein needs in his classic book, Physiological Economy in Nutrition.2 Professor Chittenden believed Dr. Voit had cause and effect reversed: people did not become prosperous because they ate high protein diets, but rather they ate meat and other expensive high protein foods because they could afford them. One hundred years ago he wrote, “We are all creatures of habit, and our palates are pleasantly excited by the rich animal foods with their high content of proteid (protein), and we may well question whether our dietetic habits are not based more upon the dictates of our palates than upon scientific reasoning or true physiological needs.”
He reasoned that we should know the minimal protein requirement for the healthy man (and woman), and believed that any protein intake beyond our requirements could cause injury to our body, especially to the liver and kidneys. As he explained it, “Fats and carbohydrates when oxidized in the body are ultimately burned to simple gaseous products…easily and quickly eliminated...” “With proteid (protein) foods…when oxidized, (they) yield a row of crystalline nitrogenous products which ultimately pass out of the body through the kidneys. (These nitrogen-based protein byproducts) – frequently spoken of as toxins – float about through the body and may exercise more or less of a deleterious influence upon the system, or, being temporarily deposited, may exert some specific or local influence that calls for their speedy removal.” With these few words Professor Chittenden explained the deleterious effects of diets high in protein and meat – consequences too few practicing doctors know about today.
The First Scientific Experiments on Our Protein Needs
Professor Chittenden’s first experiment was on himself. For nine months, he recorded his own body weight, which decreased from 143 pounds (65 Kg) to 128 pounds (58 kg) on his new diet of one-third the protein that Dr. Voit recommended. Chittenden's health remained excellent and he described his condition as being with “greater freedom from fatigue and muscular soreness than in previous years of a fuller dietary.” He had suffered from arthritis of his knee and discovered that by reducing his intake of meat his condition disappeared and his “sick headaches” and bilious attacks (abdominal pains) no longer appeared periodically as before; plus he fully maintained his mental and physical activity, with a protein intake of about 40 grams a day.
Chittenden performed valid scientific studies by collecting data on the daily dietary and urine histories of his subjects (including himself) to determine protein utilization. Because he was contradicting the known “truths” of his time, he proceeded with extreme caution with his further investigations. He organized three controlled trials with increasing demands for testing the adequacy of diets lower in protein than commonly recommended.
The first trial involved a group of five men connected with Yale University, leading active lives but not engaged in very muscular work. On a low-protein diet (62 grams daily) for 6 months, they all remained healthy and in positive nitrogen balance (more protein went into, than out of, their bodies). The second trial used 13 male volunteers from the Hospital Corps of the U.S. army. They were described as doing moderate work with one day of vigorous activity at the gymnasium. They remained in good health on 61 grams of protein daily. His final trial was with 8 Yale student athletes, some of them with exceptional records of athletic events. They ate an average of 64 grams of protein daily while maintaining their athletic endeavors, and improving their performance by a striking 35 percent. Following these studies, Chittenden in 1904 concluded that 35–50 g of protein a day was adequate for adults, and individuals could maintain their health and fitness on this amount. Studies over the past century have consistently confirmed Professor Chittenden’s findings, yet you would hardly know it with the present day popularity of high protein diets.
Rats Confuse Nutritionists
Many people have the idea that animal foods contain protein which is superior in quality to the protein found in plants. This misconception dates back to l9l4, when Lafayette B. Mendel and Thomas B. Osborne studied the protein requirements of laboratory rats and demonstrated nutritional requirements for the individual amino acids.5 They found that rats grew better on animal sources of protein than on vegetable sources. So, investigators at that time suspected that the vegetable foods had insufficient amounts of some of the amino acids essential for the normal growth of rats. Because of these and other animal-based experiments, flesh, eggs, and dairy foods were classified as superior, or "Class A" protein sources. Vegetable proteins were designated inferior, or "Class B" proteins.
Studies completed in the early 1940's by Dr. William Rose of the University of Illinois found that l0 amino acids were essential for a rat’s diet.6 The removal of any one of these essential amino acids from the food of growing rats led to profound nutritive failure, accompanied by a rapid decline in weight, loss of appetite, and eventually death. Animal products, such as meat, poultry, milk, and eggs prevented this decline in the rats’ health, and were found to contain the l0 essential amino acids in just the right proportions for needs of growing rats. Based on these early rat experiments the amino acid pattern found in animal products was declared to be the “gold standard” by which to compare the amino acid pattern of vegetable foods. According to this concept, wheat and rice were declared deficient in lysine and corn was deficient in tryptophan.
Subsequent research has shown the obvious: the initial premise, that animal products supply the most ideal protein pattern for humans, as they do for rats, is incorrect.7 The dietary needs of rats are considerably different from those of humans, mainly because rats grow very rapidly into adult size as compared to people. Rats are fully adult after 6 months; whereas a person takes 17 years to fully mature. This difference in need is especially clear when the breast milk of both species is examined and compared. The protein content of rat breast milk is 10 times greater than the milk intended for human babies.8,9 Baby rats double in size in 4.5 days; an infant doubles in size in 6 months. The obvious reason for the different needs is because rats grow very rapidly into adult size as compared to humans; therefore requirements for protein to support that growth are very much higher.
Dr. William Rose Discovers Human Needs
In 1942, Dr. William Rose turned his attention from rats to people and began studying the amino acid requirements for humans using basically the same methodology he had used with rats. Healthy, male graduate students, grateful in those days for the free food, the dollar a day they were paid and the prospect of getting their initials in print in Rose's widely read publications, served as his experimental animals. They were fed a diet consisting of corn starch, sucrose, butter fat without protein, corn oil, inorganic salts, the known vitamins, and mixtures of highly purified amino acids. Their diet also included a large brown "candy," which contained a concentrated liver extract to supply unknown vitamins, sugar, and peppermint oil to provide a "never-to-be-forgotten taste."
The study used a chemical measurement called nitrogen balance to determine whether the subjects were getting enough usable protein from the mixture. From his experiments, Dr. Rose found that only eight of the ten amino acids essential to rats were also essential to men – we were better at making two amino acids than rats. When an essential amino acid was given in insufficient amounts for approximately two days, all subjects complained bitterly of similar symptoms: a clear increase in nervous irritability, extreme fatigue, and a profound failure of appetite. The subjects were unable to continue the amino acid deficient diets for more than a few days at a time.
Through his studies, Dr. Rose also determined a minimum level of intake for each of the eight essential amino acids.10 He found small amounts of variation in individual needs among his subjects. Because of these unexplained differences among people, he included a large margin of safety in his final conclusion on minimum amino acid requirements. For each amino acid, he took the highest recorded level of need in any subject, and then doubled that amount for a "recommended requirement" – described as a definitely safe intake. It is important to realize that his higher requirement is easily met by a diet centered around any single starchy vegetable. Even in children, as long as energy needs are satisfied by starch, protein needs are automatically satisfied in almost every situation because of the basic and complete design of the food. These investigations were completed by the spring of 1952, resulting in sixteen papers in The Journal of Biological Chemistry that are considered classic contributions in the history of nutrition for the benefit of human beings.
The results of Dr. Rose`s studies are summarized in the following chart, under "minimum requirements". From the chart, it is clear that vegetable foods contain more than enough of all the amino acids essential for humans.11
Many investigators have measured the capacity of plant foods to meet our protein needs. Their findings show that children and adults thrive on diets based on a single starch; and they grow healthy and strong.11,12 Furthermore, no improvement is obtained by mixing plant foods or supplementing with amino acid mixtures to make the combined amino acid pattern look more like that of flesh, dairy, or eggs.12 (For a thorough discussion of human protein needs see The McDougall Plan, New Win Publishers.)
Diet for a Small Planet Helps and Harms
A popular book among vegetarians, Diet for a Small Planet, by Frances Moore Lappe’ published in 1971, started a revolution that has had a positive impact for the past three decades on the lives of millions of people. Unfortunately, Ms. Lappe’ failed to understand the basic scientific literature on human protein needs and the sufficiency of plants foods before she wrote her influential book. She believed plants contained “incomplete proteins” with insufficient amounts of certain essential amino acids to meet the needs of people.13 As a result of this misunderstanding, she placed great emphasis on combining vegetable foods to create an amino acid pattern which resembles that found in animal foods. This emphasis is unnecessary and implies that it is difficult to obtain “complete” protein from vegetables without detailed nutritional knowledge. Because of her complicated and incorrect ideas people are frightened away from vegetable-based diets.
The impact of her incorrect teachings of more than 30 years ago affects nutritional policy even today. In 2001 the Nutrition Committee of the American Heart Association published a long overdue review warning people of the dangers of high protein diets, like the Atkins, the Zone, and Sugar Busters diets.14 Unfortunately, this one statement in an otherwise valuable report is scientifically incorrect: “Although plant proteins form a large part of the human diet, most are deficient in 1 or more essential amino acids and are therefore regarded as incomplete proteins.” For a supporting scientific reference the Committee cites Frances Moore Lappe’s 1971 book, Diet for a Small Planet.
You may think this is a trivial matter; however, incorrect information on our protein needs can have grave consequences on your health and your family’s health. With the American Heart Association teaching that plants fail to supply complete protein you are almost certain to receive incorrect, potentially damaging, medical advice. For example, say you go to your doctor after a heart attack and mention that you are now going to become a pure vegetarian to avoid future heart trouble. Your doctor may respond, “You can’t do that, you will become protein deficient on an all plant food diet – the Heart Association says so.” Or your child is sick with recurrent asthma and ear infections and you want a dietary cure – you may be warned away from a highly effective therapy because members of the Nutrition Committee of the American Heart Association fail to understand basic scientific research about human protein needs and plant foods. So this is no small matter.
I have confronted the Heart Association about spreading misinformation that can result in suffering as serious as death from heart disease – so far they have shown no interest in making overdue corrections to their incorrect teaching. (See my July, August and November 2002 Newsletters for more information on this.) I recently shared my conflict with the Heart Association with the world’s leading authority on human protein requirements, Dr. D. Joe Millward from the Center for Nutrition and Food Safety, School of Biological Sciences University of Surrey, UK. His response to me on July 10, 2003 was, “Contrary to general opinion, the distinction between dietary protein sources in terms of the nutritional superiority of animal over plant proteins is much more difficult to demonstrate and less relevant in human nutrition. This is quite distinct from the AHA position which in my view is wrong.” 15
So How Do You Know the Truth about Your Protein Needs?
Read the scientific literature www.nlm.nih.gov and look at the world picture. Notice that 60 percent of people alive today and most of the people who have lived in the past have obtained their protein from plant foods. They have lived successfully; avoiding all the diseases common in our society. Even today plant sources provide 65% of the world supply of the protein we eat.
What about the starving children in Africa? The picture one often sees of “protein deficient” children in famine areas of Asia or Africa is actually one of starvation and is more accurately described as “calorie deficiency.”11 When these children come under medical supervision, they are nourished back to health with their local diets of corn, wheat, rice, and/or beans. Children recovering from starvation grow up to l8 times faster than usual and require a higher protein content to provide for their catch-up in development – and plant foods easily provide this extra amount of protein. Even very-low protein starchy root crops, such as casava root, are sufficient enough in nutrients, including protein, to keep people healthy.3
The World Health Organization knows the truth. Since 1974 it has recommended that adults consume a diet with 5% of the calories from protein – this would mean 38 grams of protein for a man burning 3000 calories a day and 29 grams for a woman using 2300 calories a day. These minimum requirements provide for a large margin of safety that easily covers people who theoretically could have greater protein needs – such as accident victims or people with infections. This quantity of protein is almost impossible to avoid if enough whole plant food is consumed to meet daily calorie needs. For example, rice alone would provide 71 grams of highly useable protein and white potatoes would provide 64 grams of protein for a working man.16 For a pregnant woman the WHO recommends 6% of the calories come from protein – again an amount of protein easily provided by a diet based on starches, vegetables, and fruits.
Human Breast Milk – Your Final Assurance
Your greatest need for protein is when you grow the most. The greatest time of growth in a human being’s life is as an infant. We double in size during the first 6 months. The ideal food for a baby is mother’s milk. Therefore, breast milk is the “gold standard” for nutrition – during your time of greatest need for all nutrients, including protein. Five to 6.3 percent of the calories in human breast milk are from protein.9,17 This is the maximum concentration of protein we will ever need in our food supply. Knowing this value tells us that at no other time in our life will we ever require more protein. Consider the protein content of the foods we consume after weaning – these are even higher in protein – rice is 9%, potatoes are 8%, corn is 11% and oatmeal is 15% protein.16
Wrong Thinking Ruins Health
Even though all the scientific knowledge accumulated over the past 100 years clearly shows our bodies were designed to live best on a diet lower in protein than dictated by common belief, we continue on the same disastrous dietary path. As Russell Henry Chittenden explained 100 years ago, “The poorer man emulates his richer neighbors as soon as his circumstances permit, and resources that could be much more advantageously expended for the good of the family and the home are practically wasted – to say nothing of possible injury to health – under the mistaken idea that this more generous method of living (a high-protein, high-meat diet) is the surest road to health and strength.”2 Dr. Chittenden also believed that knowledge and the truth would prevail. He wrote, “Habit and sentiment play such a part in our lives that it is too much to expect any sudden change in custom. By a proper education commenced early in life it may, however, be possible to establish new standards, which in time may prevail and eventually lead to more enlightened methods of living...” The past century of declining health for people living in developed countries has proved Chittenden wrong – so far. However, with widespread communication via the Internet his predictions may soon become reality.
1) Carpenter K. A short history of nutritional science: part 2 (1885-1912). J Nutr. 2003 Apr;133(4):975-84.
2) Chittenden, R. H. (1904). Physiological economy in nutrition, with special reference to the minimal protein requirement of the healthy man. An experimental study. New York: Frederick A. Stokes Company.
3) Millward DJ. The nutritional value of plant-based diets in relation to human amino acid and protein requirements. Proc Nutr Soc. 1999 May;58(2):249-60.
4) Millward DJ. Metabolic demands for amino acids and the human dietary requirement: Millward and Rivers (1988) revisited. J Nutr. 1998 Dec;128(12 Suppl):2563S-2576S.
5) Osborne T. Amino-acids in nutrition and growth. J Bio Chem. 1914; 17:325-49.
6) Rose W. Comparative growth of diet containing ten and nineteen amino acids, with further observation upon the role of glutamic and aspartic acid. J Bio Chem. 1948; 176: 753-62.
7) Bicker M. The protein requirement of adult rats in terms of the protein contained in egg, milk, and soy flour. J Nutr 1947;34: 491.
8) Bell G. Textbook of Physiology and Biochemestry, 4th ed., Williams and Wilkins, Baltimore, 1959, p. 12.
9) Reeds PJ. Protein nutrition of the neonate. Proc Nutr Soc. 2000 Feb;59(1):87-97.
10) Rose W. The amino acid requirement of adult man. Nutr Abst Rev. 1957;27:63l-47.
11) McDougall J. (1983). The McDougall Plan. Clinton, NJ. New Win Publishing.
12) M. Irwin, Hegsted D. A conspectus of research on protein requirements of man. J Nutr. 1971;101:385-428.
13) Moyer G. Frances Moore Lappe’s new edition says it all. Nutrition Action, Oct. 1982. p. 10-11.
14) St. Jeor S, Howard B, Prewitt E. Dietary protein and weight reduction. A statement for health professionals from the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation 2001;104:1869-74.
15) Personal Communication with John McDougall, MD on July 10, 2003.
16) J Pennington. Bowes & Church’s Food Values of Portions Commonly Used. 17th Ed. Lippincott. Philadelphia- New York. 1998.
17) Reeds PJ. Protein and amino acid requirements and the composition of complementary foods. J Nutr. 2003 Sep;133(9):2953S-61S.
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