by Dr. John McDougall (excerpted)
For the entire article, see: https://www.drmcdougall.com/misc/2007nl/apr/protein.htm
Preface: Dr. John McDougall, M.D., teaches people to eat a plant based diet consisting of fruits, vegetable, grains, beans, nuts, seeds, unrefined foods, and low fat/low sugar. His emphasis is on complex carbohydrates. People loose weight on his all-you-want-to-eat diet. He is able to get most people off all their medications with this healthy eating plan. The full article has much more great information, but there is no room here to present all of it. Dr. McDougall frequently gets asked, “Where do you get your protein”? Enjoy!
Proteins are made from chains of 20 different amino acids that connect together in varying sequences—similar to how all the words in a dictionary are made from the same 26 letters. Plants (and microorganisms) can synthesize all of the individual amino acids that are used to build proteins, but animals cannot. There are 8 amino acids that people cannot make and thus, these must be obtained from our diets—they are referred to as “essential.”
After we eat our foods, stomach acids and intestinal enzymes digest the proteins into individual amino acids. These components are then absorbed through the intestinal walls into the bloodstream. After entering the body’s cells, these amino acids are reassembled into proteins. Proteins function as structural materials which build the scaffolds that maintain cell shapes, enzymes which catalyze biochemical reactions, and hormones which signal messages between cells—to name only a few of their vital roles.
Since plants are made up of structurally sound cells with enzymes and hormones, they are by nature rich sources of proteins. In fact, so rich are plants that they can meet the protein needs of the earth’s largest animals: elephants, hippopotamuses, giraffes, and cows. You would be correct to deduce that the protein needs of relatively small humans can easily be met by plants.
The World Health Organization (WHO) recommends that men and women obtain 5% of their calories as 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. This quantity of protein is impossible to avoid when daily calorie needs are met by unrefined starches and vegetables. For example, rice alone would provide 71 grams of highly useable protein and white potatoes would provide 64 grams of protein.8
Our greatest time of growth, thus the time of our greatest need for protein, is during our first 2 years of life. We double in size. At this vigorous developmental stage our ideal food is human milk, which is 5% protein. Compare this need to food choices that should be made as adults, when we are not growing. Rice is 8% protein, corn 11%, oatmeal 15%, and beans 27%. Thus, protein deficiency is impossible when calorie needs are met by eating unprocessed starches and vegetables.
The healthy active lives of hundreds of millions of people laboring in Asia, Africa, and Central and South America on diets with less than half the amount of protein eaten by Americans and Europeans prove that the popular understanding of our protein needs is seriously flawed.
Unlike fat, protein cannot be stored. When it is consumed in excess of our needs, protein is broken down mostly by the liver, and partly by the kidneys and muscles. Consumption in excess of our needs overworks the liver and kidneys, and can cause accumulation of toxic protein byproducts.
Proteins are made of amino acids, and are, therefore, acidic by nature. Animal proteins are abundant in sulfur-containing amino acids which break down into very powerful sulfuric acid. These kinds of amino acids are abundant in hard cheese, red meat, poultry, seafood, and eggs, and their acids must be neutralized by buffers found in the bones. The bones dissolve to release the buffering materials; eventually resulting in a condition of weakened bones, known as osteoporosis. Released bone materials often settle and coalesce in the kidney system, causing kidney stones. Fruits and vegetables are largely alkaline, preserving bone health and preventing kidney stones13. (A more detailed discussion of the health consequences from excess protein is found in my January 2004 newsletter article: Protein Overload.)
In 1981, 10 Irish prisoners from the Republican Army (IRA) went on a hunger strike. Nine out of 10 of these men died between 57 and 73 days (mean of 61.6 days) of starvation after losing about 40% of their body weights (the remaining striker died of complications of a gunshot wound).16,17 This experience gave doctors a chance to observe first-hand the metabolic changes that occur during starvation. Protein stores were generally protected during starvation, with most of the energy to stay alive being derived from the men’s fat stores. It was estimated that the hunger strikers had lost up to 94% of their body-fat levels, but only 19% of their body-protein levels at the time of death.16 They died when they ran out of fat. Since fat is more critical than protein, people should be asking, “Where do you get your fat (on any diet)?
8 J Pennington. Bowes & Church’s Food Values of Portions Commonly Used. 17th Ed. Lippincott. Philadelphia- New York. 1998.
16 Leiter LA, Marliss EB. Survival during fasting may depend on fat as well as protein stores. JAMA 1982;248:2306
17 ZSurvival. Ann Intern Med. 1997 Sep 1;127(5):405-9.