The Great Meat and Protein Myth
Protein was discovered as a nutrient class in 1838.5 By then, it was also recognized that proteins were associated with all forms of life from the simplest single-celled organisms to man. No wonder there has been such fascination with protein?anything that is necessary for all forms of life is truly awe inspiring. In fact, Webster suggests that the very word "protein" is derived from the Greek root "protos" which means "first." Our appreciation for protein has grown over the years; we now know that it is vital for such diverse roles as muscle function, hormone synthesis, and the production of enzymes. Furthermore, our need for protein is increased during our growth years, during the repair of tissues (after an injury or surgery, for example), and during muscle-building exercise.
Thus there is no myth regarding the importance of protein in our diet. However, the confusion about the so-called superiority of animal protein sources emerges when we look a little closer at the nature of proteins. Proteins are complex molecules that are made up of molecular building blocks called "amino acids." There are 20 amino acids that the human body uses to build the proteins it needs for life and health. In adult humans, eight of these amino acids are called essential, because they must come from the diet. The names of these amino acids are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The remaining 12 amino acids can be made by the human body. If we compare a protein molecule to a train, the amino acids are like the individual cars of the train. Just as a train cannot be built out of all box cars or all cabooses, so the body needs amino acids in the right proportions to construct functional protein molecules. At this point, animal protein bias begins to creep in. It is obvious that animals are physiologically more like humans than plants are. Therefore, it should come as no surprise that in comparing meat from a single animal species (like beef) with food from a single plant species (like oatmeal), the mixture of amino acids in the animal product will tend to be closer to the proportions in which humans need them. Because of this, many have incorrectly reasoned that a diet based on animal protein sources like meat is superior to a diet based on plant products in providing adequate amounts of the essential amino acids in the right proportions.
This brings us back to the basic question: do animal sources of nutrition provide better "quality" protein than plant sources? If you look at the diet as a whole, the answer is no. This is exactly what Hardinge and Stare found in their classic research in the 1960s.11 They looked at the complete diets of three groups: meat-eating Americans, pure vegetarians (those who excluded all animal products from their diet), and lacto-ovo vegetarians (those who excluded all animal products except for dairy products and eggs). The researchers measured the actual amount of each amino acid consumed by each of these groups from their whole diets. They then compared that intake with the ideal balance of amino acids needed by man according to two standards: (1) the standard determined by Dr. Rose in the 1940s and 50s and still used by the World Health Organization to this day, and (2) human breast milk. The only food specifically designed to meet all the amino acid needs of a human is human breast milk. Amazingly, the best quality protein among the three complete diets was the pure vegetarian diet.
The protein content of milk is an indication of the protein requirement of a new-born, whether that new-born is human or animal. Let us examine the differences in amount of protein in milk in the different mammalian species. They are tabulated in figure.
This comparison demonstrates that humans actually need less protein than the animals on the list. Notice that the relative growth rate is greater in those that have greater amounts of protein in the milk, as would be expected, because of the greater protein requirement to build body tissue. If a human consumed a rat´s milk from birth, would that baby be able to double its birth weight in days instead of months? The answer is obviously no, since the rate of growth is largely genetically determined. The excess protein would not be utilized and, as we will later see, could actually harm the developing child.
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Positive by Neil Nedley