A vegetarian diet may help reduce your risk of cancer of the colon and rectum by as much as 20%. If you add some fish to your menu, the risk appears to be cut even further, according to a large observational study.
The study, Adventist Health Study 2, enrolled 77,659 people between 2002 and 2007. The enrollees were members of the Seventh-day Adventist Church, a protestant Christian denomination that recommends vegetarianism and abstaining from pork, tobacco, and alcohol. However, about half of the participants said they ate meat. The rest of the participants were divided into those who followed a vegan diet and ate no meat, eggs, or dairy; vegetarians who ate eggs and dairy; vegetarians who ate fish; and semi-vegetarians who ate meat less than once a week.
The average follow-up was 7.3 years and 490 cases of colon or rectal cancer were diagnosed during follow-up.
All vegetarians had a 22% reduction in risk of developing colorectal cancer, with a 19% lower risk of colon cancer and a 29% lower risk for rectal cancer, than did the people who age meat. People who ate fish and vegetables had a 43% lower risk compared to non-vegetarians. Vegans and vegetarians who ate eggs and dairy had a risk that was 16% to 18% lower, while semi-vegetarians had an 8% lower risk.
This study is an observational study, which means that it found an association between eating vegetarian and a reduced risk of colorectal cancer, but the study does not show evidence that there is a cause and effect. People who are Seventh-day Adventists are supposed to follow other aspects of a healthy lifestyle, such as avoiding tobacco and alcohol which can play a role in reducing the risk of cancer. The study also does not show any evidence of why a meatless or reduced meat diet would help reduce cancer risk.
The study was published in JAMA Internal Medicine.