Grapefruit Linked to Breast Cancer

Grapefruit is known to interact with more than 60% of all medications taken by mouth, including hormones such as progesterone and estrogen. We also know that higher levels of female hormones are associated with an increased risk of breast cancer. A study just released in the British Journal of Cancer (10 July 2007(97):440-445) investigates this link.

This large-scale, multi-aim study initially included over 200,000 men and women in Los Angeles, California and Hawaii. All were between 45 and 75 years of age at the initial phase of the study, between 1993 and 1996. After excluding men, women who were not postmenopausal, and women already diagnosed with any type of cancer, over 46,000 women remained.

Among other dietary and lifestyle information, the women were asked how often they ate "grapefruit or pomelo" during the past year, and how much they usually ate when they did. The eight possible answers ranged from "never or hardly ever," to "once a week" or as much as "2 or more times per day." In addition, the women were asked about their hormone therapy use, if any.

At the end of 2002, almost ten years later, the number of diagnosed breast cancer cases were correlated with the relative levels of grapefruit a woman ate and the woman's use of hormone therapy. After allowing for such variables as Body Mass Index, exercise level, and dietary items other than grapefruit, the scientists were sobered to find that eating 1/4 or more of a grapefruit each day, the highest level of consumption in the study, was strongly associated with a 30% increase in a woman's risk of breast cancer. This held true regardless of a woman's Body Mass Index and hormone therapy use, both of which are known to increase a woman's risk of breast cancer.

What this means for you

The scientists note that this is the first specific food that has been shown to increase the risk of breast cancer in postmenopausal women. While there's no need to ban grapefruit from every woman's life, I will be telling those of my patients who are already at an increased risk of breast cancer to consider not eating as much of both grapefruit and grapefruit juice.

First posted: July 18 2007