%. Dr. Campbell's team also found that hepatitis B virus, which is known to be a carcinogen that causes liver cancer, does not cause as much damage in rats which were given a diet with 5 % protein when compared to rats fed with a diet containing 20 % protein.
The Chinese on average consumed less than 10 % of protein from their diet, among which 90 % of protein comes from plants. On the other hand Americans consumed more than 15 % of protein in their diet, among which more than 80 % comes from animal source. This difference in protein content may cause at least seven-fold difference in cancer risk. A diet with high animal protein increases risk of breast cancer. Similarly a diet rich in red meat and processed meat resulted in an elevated risk of colon cancer. Link between dairy products and prostate cancer has already been established.