Colorectal cancer is the second most common cancer in the United States and is expected to cause close to 50,000 deaths in 2015. However, a new observational study has found that a vegetarian diet could significantly reduce the risk of developing the disease.
The new study found that vegetarian diets are associated with a lower risk of colorectal cancer. Previous studies have found that high red meat consumption is associated with an increased risk of colorectal cancer. However, the effect of various types of meatless or vegetarian diets is less well known.
The new prospective cohort study followed 78,000 adults for a mean of seven years, during which 490 developed colorectal cancer. Participants were characterized based on a validated food frequency questionnaires and categorized into five dietary patterns.
- Vegan (does not eat eggs, dairy, fish, or meat)
- Lacto-ovo vegetarian (eats milk and eggs but not meat)
- Pescovegetarian (eats eggs, dairy, and fish but not meat)
- Semivegetarian (eats eggs, dairy, and limited fish plus meat less than once a week)
- Nonvegetarian (eats eggs, dairy, and fish plus meat more than one time a week)
After adjusting for demographic and clinical factors, the researchers found that individuals who ate a vegetarian diet were at a 22% lower risk of colorectal cancer, with a 19% reduced risk of colon cancer and a 29% reduced risk of rectal cancer, compared with participants who did not follow a vegetarian diet. Pescovegetarians had a 49% lower risk of colorectal cancer, lacto-ovo vegetarians had an 18% lower risk, vegans had a 16% reduced risk, and semivegetarians were 8% less likely to develop the disease.
The authors concluded that vegetarian diets are associated with an overall lower incidence of colorectal cancers. Pescovegetarians, in particular, have a much lower risk compared with nonvegetarians. If the results are causal, they may be important for primary prevention of colorectal cancers.