In a surprising finding that contradicts conventional dietary wisdom, Harvard University researchers have discovered that a high-fiber diet does not appear to reduce the risk of colon cancer. However, the researchers and other cancer specialists stress high in fiber — which vegetables and whole grains — has other health benefits that still make it worthwhile to consume.

In the study, published in the latest New England Journal of Medicine, researchers tracked the colon and rectal health of more than 88,000 women who participated in the Harvard-based Nurses Health Study from 1980 to 1996. Of the women studied, 787 developed colon or rectal cancer. The risk was the same, regardless of how much fiber they ate.

The researchers said they were astounded by the findings, which contradict the conventional thinking about the link between fiber and colon cancer. However, previous similar studies in men also found that fiber does not lower the risk of colon cancer, and the researchers said they believe their new findings would also apply to men.

The recommended amount of fiber for a healthy diet is about 30 grams per day, about five to eight servings of fruits and vegetables. One researcher said he doubts his organization will change its nutritional guidelines because people who eat more fiber generally suffer fewer cases of other types of cancer. He also stressed that there may be other properties of vegetables, including the vitamin folate, that could lower the risk of cancer and that people who eat more fruits, vegetables and whole grains also tend to be less obese and suffer fewer health problems.

The researchers were quick to say that fiber is not necessarily a bad thing. “It is still helpful, but not for colon cancer,” they said. In addition a high-fiber diet has been shown to prevent other types of cancer, including that of the mouth, pharynx, larynx, esophagus and stomach. But none of these are as common as colorectal cancer, which is the second leading cancer among Americans with 57,000 deaths in 1998 (lung cancer is the number one killing cancer).

The researchers noted that the study had its limitations. For example, many scientists believe that men and women respond differently to dietary fat and fiber, and the study group involved only women. Still, the new study adds to growing research that suggests when it comes to colorectal cancer the benefits of fiber have yet to be proven.