The question is a frequent one.
The real questions about protein in the diet should be:
How much protein should I eat?
What kind of protein is optimal for human health?
Who is the beneficiary of the research that supports a nutrition statistic? Who makes the most money or who funded the research? Call me skeptical but I think that is worth adding to the total evaluation.
How Much Protein Should I Eat? Bottom Line Answer = about 10% of your daily calories should come from protein.
Dr. John McDougal is a respected resource for nutrition education. In his work Common Sense Nutrition his guideline is 8 to 15% of total daily calories from protein. Many other Functional Medicine health care providers concur with that number. The Institute Of Medicine and World Health Organization recommend 10% calories from protein; 0.8 to 0.83 grams/kg/day. 0.8 grams per kilogram equals .36 grams per pound, as one kilo equals 2.2 pounds.
Example: 110 pound body weight = 40 grams of protein
150 pound body weight = 55 grams of protein
Athletes and body builders may be able to utilize higher protein intakes during high competition and muscle building phases of their training season.
Eating Too Much Protein
When you eat more protein than your body utilizes to form structures, it gets converted to carbohydrate. Then the carbohydrate moves into glycogen storage. When glycogen stores are filled, excess nutrients are converted by the liver and stored as triglycerides in fat tissues.1
T. Colin Campbell, the respected researcher from Cornell and author of The China Study writes “The correct recommended intake is around 8-10% protein (not 35%!) which can be easily supplied by a good whole foods plant based diet. Even potatoes will do the job alone.
So, it’s back to the question of how and why and who is recommending [higher] numbers. The first time that these new high limits appeared was when a top consultant to the dairy industry, was chairing the Food and Nutrition Board that was responsible for the report. That report was funded by the dairy industry-based Dannon Institute, among other corporate benefactors who, accidentally I suppose, rather liked these high protein recommendations. “2
Generally, all food sourced proteins are digested to individual amino acids and absorbed.
Although there are dozens of naturally occurring amino acids, the proteins in our body are derived from just twenty. Of these twenty amino acids, our body is able to adequately synthesize twelve by combining nutrients. The other eight amino acids, called essential amino acids, must be supplied by our diet. 3
My Side Note: Human Mother’s milk supplies 6% of calories from protein. Cow’s milk provides an excessive 26%.4
The Surprise Hidden Protein Source In Your Body
In addition to protein we eat there is an internal source of amino acids. Endogenous amino acids are derived from the sloughing of intestinal cells and used up digestive enzymes. These recycled proteins are a rich source of essential amino acids. We now know that the body is quite capable of taking incomplete proteins and making them complete by utilizing this recycling mechanism. It is now clear that more than 200 grams of endogenous protein is added to the daily dietary protein. Given the recommended daily intake is about 0.8 grams per kilogram of body weight, for a 150 pound person that is 55 grams. The important fact here is that the majority of amino acids absorbed from the intestinal tract are derived from recycled body protein.5
Are We Built to Eat Meat As Our Primary Protein Source?
All natural foods-from lettuce to nuts-contain varying amounts of protein. Most conventional nutritional thinking ignores the tremendous contribution of plant foods to our protein needs.
Even a brief look at comparative anatomy illustrates quite clearly that man is not designed to be an obligatory carnivore. And just because our bodies have a vital need for a substance does not mean that twice or three times our need is even better.
A diet of sufficient caloric intake derived from fresh fruits and vegetables with the variable addition of nuts, whole grains and legumes will provide an optimum intake of protein and other nutrients, depending upon the particular foods eaten.6
Bottom Line = Humans are omnivores. We can eat and utilize nutrients from animal food as well as plant food.7 The most healthful diet appears to be from predominantly plant foods. Some proponents of a plant based diet also acknowledge that eating 2 to 3 servings weekly of meat, fish or animal protein as 3 to 4 ounce servings is acceptable in a healthful diet.
3) http://www.bodyrecomposition.com/the-protein-book Lyle McDonald