Women who follow a typical “Western” diet—characterized by higher intakes of processed and red meats, refined grains, sweets, and desserts—may be more likely to develop colon cancer, according to new research.

Teresa Fung, ScD, and colleagues from Harvard University reached this conclusion after following more than 75,000 women for a period of 12 years. They published their results in the Archives of Internal Medicine (Vol. 163: 309-314).

The idea of a connection between diet and cancer is not new. In fact, it is estimated that about one third of all the cancer deaths in the US each year can be attributed to diet and physical activity habits.

Among the various types of cancers, colorectal cancer seems most likely to be influenced by what people eat. Many studies have linked colorectal cancer to poor eating habits, but teasing out exactly what increases the risk has been difficult.

Several studies have found that diets high in vegetables and fruits may be linked to decreased risk, while diets high in red meat have been associated with an increased risk.

Researchers are trying to determine if antioxidants (or lack thereof), fiber, or some other nutrients are responsible for the effect. Newer laboratory techniques are now allowing them to make slow but steady progress on a molecular level.

For the current study, instead of looking at the effects of particular foods, the researchers decided to examine overall dietary patterns. They used data from the Nurses’ Health Study, which began back in 1976.

Part of the study included filling out a dietary questionnaire every few years, beginning in 1984. The questionnaire asked how often the nurses ate 116 specific food items. More than 76,000 women completed the questionnaires up through 1994, and were followed through 1996.

The researchers assessed how closely each woman followed one of two dietary patterns. The “Western” pattern included large amounts of refined grains, processed and red meats, desserts, high-fat dairy products, and French fries. The other pattern, which the researchers termed “prudent,” consisted of more fruits and vegetables, whole grains, legumes, poultry, and fish.

After adjusting for other factors such as age, tobacco and alcohol use, and physical activity, the researchers found that women who most closely followed the Western diet were significantly more likely to develop colon cancer than those who followed it less closely.

Women who closely followed the prudent dietary pattern were less likely to develop colon cancer than those who did not, although the difference was not as strong.

Similar results have been found in most other studies, the researchers pointed out, although some did not find such a strong link. Still, the results may provide some simple suggestions for lowering risk.

“Our study provides further evidence that switching from a typical Western diet to a more prudent diet may reduce the risk of colon cancer,” they concluded.

Diet may be only one part of the overall picture in reducing colorectal cancer risk.

Until researchers are better able to pinpoint exactly how certain factors affect the way colon cancer develops, the American Cancer Society recommends making the best use of current knowledge to lower your risk. This includes increasing the intensity and duration of physical activity, eating more fruits and vegetables, limiting intake of red meats, avoiding obesity, and avoiding excessive alcohol consumption.