Type of dietary carbohydrate may impact colon cancer prognosis

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Survivors of colon cancer whose diets are heavy in complex sugars and carbohydrate-rich foods are more likely to have a recurrence of the disease than are patients who eat a better balanced diet, according to a new study from the Dana-Farber Cancer Institute. Furthermore, the impact of these dietary factors was found to be especially strong among overweight and obese patients.

The observational study is among the first to look at the impact that specific nutrients have on the likelihood of disease recurrence in people with colon cancer. Researchers analyzed data from more than 1,000 stage 3 colon cancer patients who had undergone surgery and chemotherapy. (Stage 3 colon cancer is diagnosed when the cancer has spread to the local lymph nodes but is not widespread, and has a 5-year survival rate of just over 50 percent.) All of the patients had provided detailed information regarding their diet during and six months after the trial.

Researchers assessed the impact of carbohydrates, glycemic loads (GL) and glycemic indexes (GI) on colon cancer development, finding that participants with the highest levels of GL and carbohydrate intake had an 80 percent increased risk of colon cancer recurrence or death compared with those who had the lowest levels. (GI and GL measure which certain types of carbohydrates effect the levels of glucose and insulin in the blood.) The findings were published online in the Journal of the National Cancer Institute.

Some scientists think insulin may play a critical role in colon cancer recurrence by fueling the growth of cancer cells and preventing programmed cell death, an essential process in normal cells that can go awry in cancer cells. Dr. Jeffrey A. Meyerhardt, lead author of the study and associate professor of medicine at the Dana-Farber Cancer Institute in Boston, says It s not simply that all carbs are bad or that you should avoid all sugar. It s not as simple as sugar causes cancer to grow. Different carbs and sugar lead to different responses in your body. I think people should focus on a well-balanced diet and substitute foods associated with lower glycemic loads or carbs for foods that have higher levels.

ACSH s Dr. Ruth Kava notes There s no way that this type of observational study can support a cause-and-effect relationship. In addition, dietary intake data are difficult to validate. Having said that, there s no problem with advocating a well-balanced diet for colon cancer survivors.