March 16, 1999
Web posted at: 3:59 p.m. EST (2059 GMT)

NEW YORK (CNN) -- What we eat is a major factor in our health: For instance, a diet low in fat is known to reduce the risk of heart disease. Now two major medical institutions differ on whether or not a low-fat diet can help do the same with breast cancer.

It has been theorized that dietary fat increases the risk of breast cancer by elevating the amount of estrogen and related sex hormones in the body. But most medical studies on total fat intake and breast cancer risk have been inconclusive.

Now a study published in this week's Journal of the National Cancer Institute (NCI) draws the opposite conclusion of a study published in last week's Journal of the American Medical Association (JAMA) and reported by CNN.

In the NCI report, researchers from the University of Southern California (USC) Medical School in Los Angeles say cutting fat calories may reduce the risk of breast cancer.

The researchers in the NCI article pooled the results of 13 different studies on breast cancer and diet to come up with their findings.

Dr. Michelle Holmes, who led the 14-year study contradicted by the NCI journal article, sees a problem with the USC research.

"Because of problems with the individual studies, which included lack of comparison groups, confusion with weight loss and fiber intake, and the fact that they are a very short duration, I think the results of the larger analysis are inconclusive," Holmes said.

In an accompanying editorial in the NCI journal, the authors noted there are many factors to consider when evaluating how diets affect health. They recommend that in future studies researchers need to consider other factors such as intake of fat, fiber, total energy and changes in subject weight.

Researchers for USC were not available for comment.

In last week's JAMA article, researchers of Harvard University Medical School and Brigham and Women's Hospital in Boston found no evidence that a low-fat diet helps reduce a woman's risk of breast cancer.

A low-fat diet is considered to be the consumption of less than 20 percent of daily calories from fat.

"We found no evidence that lower intake of total fat or particular types of fat over 14 years of follow-up was associated with decreased risk of breast cancer," the researchers concluded in the JAMA article.

For now, doctors agree that a diet low in fat is the best plan for overall health but not one specifically targeted at lowering breast cancer risk.

"Women should be worrying about heart disease risk when they're thinking about fat intake," Holmes said.