Grapefruit and Breast Cancer
Today someone asked me if eating grapefruit increases a person’s risk of getting breast cancer. Truthfully, I had never even heard of this being a possibility, so I did a little research. This is what I found:
Grapefruit juice was first found to contain a chemical compound that can inhibit the enzymes the body uses to breakdown certain medications in 1989. Since then, grapefruit and its juice have been found to interact with a number of different drugs, including estrogen. In 2006, the Food and Drug Administration (FDA) mandated that all hormone products for postmenopausal women be labeled to include a warning that grapefruit juice might increase blood levels of estrogen. Knowing that estrogen exposure increases breast cancer risk, Kristine Monroe, PhD, an epidemiologist at USC, decided to conduct a study to see if there was a link between eating grapefruit and breast cancer.
To do this, Monroe and her colleagues analyzed the food questionnaires collected by the Hawaii-Los Angeles Multiethnic Cohort Study (MEC), a prospective study of diet and cancer involving 212,000 people from 5 racial-ethnic groups. They identified 46,080 postmenopausal women in this study, of which 1657 had developed breast cancer. Next, they looked at how much grapefruit these women ate. However, they could not assess how often the women drank grapefruit juice because it was combined with orange juice on the food questionnaire. Based on this, Monroe concluded that eating 1/4 of a grapefruit a day or more was associated with a 30% increase in breast cancer risk. Monroe admits that these findings need to be confirmed in other studies before they can be taken seriously. She also points out that these findings are only relevant to postmenopausal women because they did not study premenopausal women.
When it comes to medical research, one study is not enough to confirm that anything is true. Many studies need to be done in different ways to validate the findings. I thought the study was poorly conducted for many reasons, but mostly because there was no way of knowing from the questionnaire whether the women had drank grapefruit juice or orange juice. Based on this information, I would say it’s safe to say that there is no proof that grapefruit increases breast cancer risk.
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