I am a healthy 85-year-old physician whose life is devoted to achieving Healthy Longevity by good nutrition that includes fasting for good health. I am the author of Physician’s Notebooks, which anyone may access free by clicking the URL at the end of this post.
First, you should know that protein is one of the 3 major nutrients in our food along with carbohydrates and fats. Protein is unique because it always contains the element nitrogen (N) usually in its amino group (-NH2) form in amino acids (the basic building block of all protein) and, as the 21 different amino acids, the chemical products of the DNA in genes by the famous genetic code.
Proteins, in contrast to carbohydrates and fats, have the greatest importance in structural functions. They can produce energy by oxidation but therein lies their risk of toxicity because our energy needs should be fulfilled by oxidation of carbohydrates and fats.
When proteins are burned for energy in oxidation, they lose their amino group and get converted into ketones and acids which produce a disease state known as ketoacidosis. This is typically seen in starvation or in untreated diabetes mellitus (chemical starvation) when, in the absence of food or (in diabetes) the inability to oxidize carbohydrates and fats, the body starts breaking down its protein structures and oxidizes them for energy. In a severe state, ketoacidosis, like untreated diabetes, will result in death after several days.
This is a risk of prolonged fasting (more than several days) or refusing to treat diabetes mellitus.
Another toxicity of protein is due to its structure of amino acids – the famous 21 – and several of these are “essential,” i.e., they cannot be made in the human body so must be included in the diet. Strict vegetarians/vegans have a higher risk of this kind of protein toxicity because vegetable protein is low in several essential amino acids. So vegetarians/vegans more easily get certain amino acid deficiency syndromes, the most famous of which is pernicious anemia due to an enzyme deficiency coming from the vegetarian protein diet. Most vegetarians avoid this by eating dairy products or taking iron and vitamin B12 supplements.
Nutritional yeast is another excellent source of vitamin B12.
Certain amino acids can be highly toxic because of genetic conditions. Most famous is phenylketonuria due to a block in the metabolism of the amino acid, phenylalanine, which then piles up in the body and produces catastrophic illness. This condition is a form of protein toxicity and can be treated by avoiding proteins that have too much phenylalanine. (Contained in the amino acids in meat, dairy, egg)
Another protein toxicity comes from the use of dietary tryptophan supplements in persons with rare genetic conditions. It has caused epidemic myalgia (muscle pain) in outbreaks among health-food addicts that use L-tryptophan supplements.
Finally, a point about protein metabolism that makes overconsuming protein problematic is that the body has no way of storing protein, as it stores carbohydrate in starch or fat in triglycerides. So it is constantly breaking down excess protein and converting its amino acids into urea and ammonia to get rid of the nitrogen.
Both of these are toxic end products and must be excreted quickly, or they will cause brain disease (ammonia) or kidney failure (urea in uremia needing dialysis). Too much protein in your food stresses the liver and the kidneys, and if you already have liver or kidney failure, a high protein diet makes it worse. In fact, kidney dialysis may sometimes be avoided by strict, balanced lower protein diets. But such diets need careful nutritionist guidance to be sure they do not produce amino acid deficiencies and also that they contain enough calories from carbohydrate and fats to protect the protein from being used for energy.
Allow me to end by reassuring the reader that if you are in reasonably good health, there is little or no risk from eating even a high protein diet. But always be sure it is balanced with enough carbohydrate to provide energy needs and to avoid protein or amino acid supplements. Persons with genetic conditions should know it from newborn testing (e.g., PKU urine test of all newborns) and then should follow nutritionist’s advice.
Proteins are best got from meat, but they also may be obtained by vegetarians/vegans from mushroom and beans. Some vegetarians take amino acid supplements to assure a good source of protein.
What are the Physician’s Notebooks?
Physician’s Notebooks is a blog that teaches Healthy Longevity, which means living past age 80 on one’s feet with wit and wits. Reading and rereading should bring success and happiness. It may up your IQ, SAT, TOEFL (Test of English as a Foreign Language) and MCAT scores.