As pointed out by the Chair of Harvard’s Nutrition department, plant protein is preferable to animal protein because food is a package deal. Plant protein has been associated with lower rates of heart disease and lower cholesterol.
Plant protein tends to be relatively low in methionine, an amino acid associated with premature aging and cancer. It also tends to also be relatively lower in the amino acid leucine, which may accelerate aging via the enzyme TOR. Diets high in animal protein tend to be acid forming, while diets centered around plant protein tend to be alkalizing.
Animal protein may also increases insulin levels and the risk of inflammatory bowel disease, impair artery function, and increase the risk of colon cancer. Reducing the ratio of animal to plant protein in men’s diets may also slow the progression of prostate cancer. Animal protein triggers the release of the cancer-promoting growth hormone IGF-1, apparently because the ratios of amino acids in animal proteins more closely resembles our own. This amino acid profile may also be one reason why animal protein is linked to heart disease and inflammatory arthritis. While animal proteins increase levels of IGF-1, and replacing with plant proteins brings levels down, “high quality” plant proteins such as soy may not significantly affect levels in either direction, although consuming 7-18 servings of soy foods a day may result circulating IGF-1 levels comparable to animal protein. To be safe, one one should probably eat no more than 3-5 servings of soy foods a day. Plant-based diets may be more effective at lowering IGF-1 levels than even strict caloric restriction.
The animal protein present in cow’s milk infant formula may be linked to childhood obesity later in life. Animal protein sources may also contain hormones and other endocrine disrupting chemicals linked to early puberty in girls and fertility issues in women; Neu5Gc, a foreign meat molecule associated with inflammation and heart disease; and saturated fat and cholesterol, which may explain why plant-based low carb diets don’t appear to have the same associated risks as meat-based low carb diets.
Beans, canned, sprouted, or dry, are included in the USDA Dietary Guidelines as a serving option for both the protein and vegetable categories. Gluten, the wheat protein found in many meat substitutes such as veggie chicken, and veggie hot dogs is another healthful source of protein for most people. Surprising to many, the USDA doesn’t allow eggs to be advertised as high in protein.
On average, people who eat a plant-based diet have significantly higher levels of protein plasma in their blood. In fact, vegetarians and vegans get 70% more protein than the required daily intake. Raw food diets may be deficient in protein, however, among other nutrients.
Topic summary contributed by Katie.