Q: Recently, I read an article posted on the Web site of the American Cancer Society that said grapefruit might increase a woman's risk of breast cancer. Can you comment on the study, and do you think women should avoid eating grapefruit?

KIMBERLY WALKER, Atlanta

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A: After reading the article ("More Study of Grapefruit Needed" at www.cancer.org), I contacted the lead author of the study, Kristine Monroe, an assistant professor at the Keck School of Medicine at the University of Southern California, and she gave me some background on the grapefruit/breast cancer connection.

Monroe and colleagues first studied the effect of dietary fibers on hormone levels in Mexican-American women. She was interested in looking at the various types of food fibers to see which type, if any, altered the level of estrogen in the body. Many researchers believe that estrogen is involved in the development of breast cancer and fiber might be a natural way to lower estrogen levels.

Monroe's investigation led to the conclusion that eating foods rich in both soluble and insoluble fibers significantly reduced estrogen levels. Soluble fiber is gel-like and is found in foods like beans, oats and apples; insoluble fiber is often referred to as "roughage" and is found in wheat and many vegetables. Most foods contain a mixture of both types of fiber so the researchers could not identify which particular food source of fiber was the best.

However, what really captured the attention of Monroe was that one fruit did not decrease estrogen levels, but instead, slightly increased estrogen. That fruit was grapefruit.

Monroe set out to look more closely at the grapefruit/estrogen connection by reviewing data collected on more than 45,000 postmenopausal women as part of a large multi-ethnic study of individuals living in Los Angeles and Hawaii. None of the women were diagnosed with breast cancer when the original data was collected in the mid-1990s, but by end of 2002, about 1,650 women in the study were diagnosed with breast cancer.

Monroe looked at grapefruit consumption in the women, as reported by food records. What she found was that women who ate more whole grapefruit (about one-quarter cup per day) had a 30 percent increase in breast cancer risk. This held true for lean and overweight women. Grapefruit interferes with the body's ability to metabolize many drugs; increasing drug levels in the blood. It is estimated that about 60 percent of all drugs taken by mouth interact with grapefruit.

It is feasible that grapefruit could have a similar effect on estrogen levels, and oral hormone replacement products now carry a warning that grapefruit juice might increase blood levels of estrogen. Monroe's study was the first to look at grapefruit and breast cancer, so the results of the study are considered preliminary. Monroe stresses that her study looked only at whole grapefruit and not grapefruit juice (the original food data collection lumped orange juice and grapefruit juice together so it could not be separated in her study). More research needs to be done to confirm these results, so this study should be looked at as one brick in a wall of research.

For women who wonder if they should give up eating grapefruit, it is too early to say. However, "if women are concerned, they might consider substituting grapefruit with other fruits until scientific consensus is reached," Monroe says.

Eating many different fruits is a good strategy to increase nutrient intake as well as minimize risk with any particular food.