Protein
PROTEINS are not made by eating proteins. When a protein food is eaten, the body must break down protein molecules into useable amino acids, rebuilding them into the thousands of different kinds of proteins it needs. More than 50,000 protein combinations are possible for the 100,000 or so cells that require them.
Amino Acids are commonly referred to as "the building blocks of proteins," just as monosaccharides are the building blocks of sugars, and fatty acids and glycerol are the building units of fats. The construction (anabolism) and destruction (catabolism) of proteins is a continual, non-stop body function.
For many years, it was believed that proteins were completely hydrolyzed in the intestinal lumen. It is now known that enzymes act on small peptides in the brushborders and cytoplasm of intestinal cells to form amino acids, with most of the process taking place in the duodenum and jejunum. In the stomach, the enzyme pepsin splits proteins into peptides, peptones, and large polypeptides. In the upper small intestine (duodenum), such pancreatic enzymes as trypsin, chymotrypsin, and carboxypeptidase, break these down further into smaller polypeptides and a few amino acids. In the epithelial cells of the small intestine (jejunum), enzymes called peptidases hydrolyze the polypeptides into amino acids.
The protein molecule contains carbon, hydrogen, oxygen, and about 16% nitrogen. Some may also contain sulfur and phosphorus. It is the presence of nitrogen that distinguishes a protein molecule from that of a carbohydrate or fat. Excess nitrogen is changed into a waste product, urea, in the liver, and then excreted in the urine . This process places an extra load on both the liver and the kidneys. The amino acids that are not used for the building and repair of tissues are broken down into carbon dioxide, ammonia, and water to produce energy or waste.
Another destination for excess amino acids is the Amino Acid Pool. When the number of amino acids within the body is high, the liver absorbs them and stores them for future use. Cells also have the capacity to store amino acids for short periods. When the amino acid level in the bloodstream falls, the liver deposits some of the stored amino acids back into circulation. Cells respond in the same fashion. If the amino acid content in the bloodstream falls or if other cells require certain amino acids, the cells are able to release their stored supply back into circulation. Since most of the cells synthesize more proteins than they can use, the cells are able to reconvert their proteins into amino acids and make deposits into the amino acid pool. It is this pool that few acknowledge; otherwise, it would destroy the accepted theory that complete proteins are needed at every meal. This is not a new theory. The knowledge has been available for over fifty years.
The body does not care where the amino acids come from, as long as there are enough of the right kinds for it to do the job it was designed to do. If the body does not care whether it receives its protein from animal or vegetable sources, why the controversy? Obviously, there are other mitigating circumstances. If it were only a matter of protein, there would not be a problem; but there are other factors to be considered, including how hard the body has to work to form the protein chains, other molecular structures affecting digestion, and overall health from using one source over another. The body is indeed a complex unit. All parts have to work together for the common good, and its use of protein is but one part of a complex whole.
The five essentials of life that must come from foods are: 90% glucose for fuel (from carbohydrates); 4 to 5% amino acids; 3 to 4% minerals; 1+% fatty acids; and less than 1% in vitamins. The number one prerequisite of food is for fuel. The body needs fuel to complete its metabolic processes. Flesh foods supply virtually no fuel, no carbohydrates, and no fiber. Fuel is built from carbohydrates, and fiber is needed to move it along through the intestinal tract. All to often, people are under the assumption that the number one prerequisite of food is protein and vitamins, thereby limiting the carbohydrates to the category of 1%. It is little wonder that problems develop when one tells the body what it should have rather than listening to natural dictation.
