High Protein Diet And Cancer

Protein is required by the body for proper growth, function and maintenance. Just under 0.5 g per pound of body weight daily meets the needs for most healthy individuals. Some research has linked protein intake to certain cancers, with the type of protein being the biggest factor.

Animal Studies

"The China Study," written by Dr. Colin Campbell et al, reports the results of more than 50 years of research from both animal and human studies. Much of his research concentrated on the study of cancer, specifically breast, prostate, colon and rectal. The original laboratory research by Campbell and colleagues found a link between consuming high amounts of protein -- 20 percent of total calories -- and increased cancer cell growth. These studies also found that diets containing less than 5 percent of calories from protein actually over-rode the "cancer-causing effects" of powerful carcinogens.

Animal Vs. Plant Protein

The lab studies performed by Campbell and his group used casein, or milk protein, for the original studies. Later studies used soy and wheat protein and found plant protein did not promote cancer growth, even at the higher 20 percent of total calories.

Human Studies

Population-based studies have found similar results in humans. A study published in 2006 in "American Journal of Clinical Nutrition" compared three groups: 21 sedentary individuals consuming a low-protein, low-calorie diet, 21 endurance runners and 21 sedentary individuals consuming a Western diet. The group consuming low-protein diets had lower concentrations of plasma growth factors and hormones linked to cancer than the other two groups. The "International Journal of Cancer" reported in 2007 the results of a case-control study of more than 2,400 women living in Shanghai, China. Researchers found a lower risk of endometrial cancer among women who consumed more plant protein and a higher risk in those consuming the most animal protein.

Harvard Studies

In his book, "Eat, Drink and Be Healthy", Dr. Walter Willett discusses results from the Nurses' Health Study, the Physicians' Health Study and the Health Professionals Follow-up Study, which tracked hundreds of thousands of people for over 20 years. He notes that from his research, animal protein does not appear to be linked with cancer. He believes all protein has roughly equivalent effects on health. He says it is the "protein package" that really matters. Animal proteins tend to come with saturated fat, while vegetable protein contains fiber and is low in saturated fat. If you choose to eat animal protein, "choose the leanest cuts you can find."