Another Look at Diet and Colon Cancer
Tufts University, July 2, 2001 (Reviewed: July 5, 2003)

A link between diet and colon cancer?

Scientists have long suspected that diet may affect the occurrence of colorectal cancer, but they've had a tough time determining exactly what factors in foods might make a person less likely to develop the intestinal polyps, or growths, that can progress to cancer. Several large studies have failed to find such a protective role for fruits and vegetables. But a study just published in the Journal of the National Cancer Institute suggests that adding some fruits and vegetables to an otherwise produce-poor diet might make a difference.

A recent analysis

Swedish researchers collected diet information on more than 61,000 women ages 40 to 74 enrolled in a national health survey. They then kept track of the women for almost 10 years, noting the number who developed colorectal cancer during that time. The researchers found that the women who consumed more than five servings a day of fruits and vegetables a day were about 25% less likely to develop colorectal cancer when compared to those who ate less than 2.5 servings per day.

And, taking a closer look at those in the lowest intake group, those who ate less than 1.5 servings per day were more likely to develop colorectal cancer than those who ate an average of 2.5 servings per day.

Did diet make a difference?

These results seem to suggest that a daily diet that includes several servings of fruits and vegetables can reduce the risk of colorectal cancer in some women. But other large studies, including the US-based Nurses' Health Study, have not come to the same conclusion. Why the difference?

The authors of the Swedish study point out that vitamin supplements and folic acid-fortified foods -- common in the United States, but not as widely used in Sweden -- provide additional amounts of some, though certainly not all, of the nutrients found in fruits and vegetables, and may provide an "extra layer" of protection from disease. On the other hand, adding a few servings a day to a diet otherwise short on fruits and vegetables could makes a significant health difference to people who don't routinely consume vitamin supplements and fortified foods.

Advice to consumers

Does that mean that those of us who take a daily multivitamin don't need to pay attention to what's on our plate? No - the American Cancer Society reminds consumers that even the most healthful foods can't totally insulate them from disease. While nutritionists can't promise that a produce-rich diet will reduce your risk of colorectal cancer, they do know that there are plenty of benefits to a diet that provides generous amounts of fruits and vegetables.

An estimated 90% of all cases of colorectal cancer are diagnosed in people older than 50, but the disease process takes many years to develop. Eating well-choosing a diet low in fat, high in fiber, and one that includes at least five servings a day of fruits and vegetables-is something that everyone can do, and it may just reduce their risk of many types of cancer, including colorectal cancer.

Source

Fruit, vegetables, dietary fiber, and risk of colorectal caner. P. Terry, E. Giovannucci, KB. Michels,  et al., Journal of the National Cancer Institute, 2001, vol. 93, pp. 525--533

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