A diet high in plant foods such as green vegetables, dried fruit, brown rice and legumes can dramatically reduce your risk of developing colorectal cancer, according to a California based study. The study; part of a larger research project, assessed the impact of diet on the risk of developing colorectal polyps, small growths in the bowel that may become cancerous.
The study involved a large group of Seventh Day Adventists, a group that are of particular interest to nutritionists because they tend to follow a fairly healthy diet and lifestyle, avoiding smoking, alcohol, and excessive amounts of red meat. This means that researchers can exclude these well known risk factors for various diseases from their studies, and focus on the impact of diet. The study was undertaken by Loma Linda University and the results were published in Nutrition and Cancer.
What Does the Study Show?
The study involved 2818 participants and took place over a 26 year period. In 1976-7 the participants were asked to complete a questionnaire that included, among other questions, 55 questions on their diet and the frequency with which they consumed certain foodstuffs. They were asked to state how often they ate or drank a particular substance using an eight point scale that ranged from never or almost never to more than once per day.
26 years later in 2002-4 the same participants were asked to complete a second questionnaire. As well as information on diet and lifestyle, they were asked whether they had ever had a colonoscopy, and whether they had ever been diagnosed with rectal or colon polyps. Although some people will develop colorectal polyps without ever developing colorectal cancer, many colorectal cancers do originate with polyps, so they are an indicator of cancer risk.
Although over 5000 people completed both questionnaires, the researchers only analyzed the questionnaires from those without a history of intestinal problems pre-1976, and those who said they had undergone a colonoscopy. These 2818 participants formed the study group.
After 26 years 441 of the 2818 participants had been diagnosed with colorectal polyps, which was around 16% of the study group. When the researchers linked their dietary habits with their risk of colorectal polyps it was clear that various foodstuffs such as green vegetables, dried fruit, and brown rice had a protective effect on the intestines. Some highlights from the study results showed that:
- Eating cooked green vegetables every day reduced the risk of colorectal polyps by 26% compared with eating them less than five times per week
- Eating dried fruit more than three times per week reduced the risk of colorectal polyps by 24% compared with eating it less than once per month
- Eating brown rice once per week reduced the risk of colorectal polyps by 40% compared with never, or almost never, eating it
- Eating legumes such as beans and lentils more than three times per week reduced the risk of colorectal polyps by 33% compared with eating them less than once per month
No association, positive or negative, was found between the risk of colorectal polyps and the consumption of red meat, fish, or salad. With both brown rice and legumes it was discovered that the more of these substances participants ate, the more they reduced their risk of colorectal polyps.
The study concluded that including plant foods such as cooked green vegetables, dried fruit, brown rice, and legumes in your diet can dramatically reduce your risk of developing colorectal polyps that may become colorectal cancer. They believe that this is due to the high fiber nature of these types of foods, as fiber has a protective effect on the intestines. These plant foods also naturally contain phytochemicals, which have antioxidant and anti-inflammatory properties which are both thought to protect against cancer.