Long-term high consumption of red and processed meat may increase the risk of cancer in the colon and rectum, a new study shows.

Dr. Michael J. Thun, with the American Cancer Society in Atlanta, and colleagues followed 148,610 adults, average age 63 years, who completed questionnaires in 1982 and again between 1992 and 1993 regarding their diet, exercise, medical history and other lifestyle habits.

By 2001, there were 1667 new cases of colorectal cancer, according to a report in Wednesday’s Journal of the American Medical Association.

The participants who consistently ate the most red meat and processed meats had a 50 percent higher rate colorectal cancer than those who ate the least red or processed meat.

Prolonged high consumption of poultry and fish was marginally associated with about a 25 percent lower risk of colon cancer, but not rectal cancer.

Meanwhile, in another study in the journal, European investigators report that eating a lot of fruit and vegetables doesn’t do anything to prevent breast cancer.

Dr. Petra H. M. Peeters, at University Medical Center in Utrecht, the Netherlands, and colleagues analyzed data on approximately 285,000 women ages 25 to 70 from eight European countries who were followed for an average of 5.4 years. The participants had completed dietary questionnaires.

There were 3659 cases of invasive breast cancer among this group of women.

Even though the highest intake of total fruits and vegetables was 2- to 3-times more than the lowest level of intake, the team saw no significant differences in breast cancer risk.

In an accompanying editorial, Dr. Walter C. Willett, at Harvard School of Public Health in Boston, comments that, despite the negative results for breast cancer risk, “reductions in blood pressure and epidemiological evidence for lower risks of cardiovascular disease provide sufficient reason to consume” fruits and vegetables in abundance.

Regarding the association between meat consumption and colorectal cancer, he adds, “prudence would suggest that red meat, and processed meats in particular, should be eaten sparingly to minimize risk.”

SOURCE: Journal of the American Medical Association, for January 12, 2005.