Many of us make an effort to eat multiple portions of fruits and vegetables because of the health benefits they are thought to bring: a decreased risk of cancer, among them.

Several studies have looked specifically at the relationship between breast cancer and fruit and vegetable consumption, with some finding a protective effect and others not. Most of the evidence suggesting a protective effect, however, comes from case-control studies, in which patients already diagnosed with cancer and matched controls are asked about their past eating habits. This type of study design is more susceptible to bias than prospective cohort studies, which follow a group of originally healthy individuals over time.

A new prospective cohort study, published in the January 12, 2005 edition of the Journal of the American Medical Association , examines the relationship between fruit and vegetable consumption and the incidence of breast cancer among women in several European countries. To their disappointment, the researchers found no association between fruit and vegetable intake and breast cancer risk.

About the Study

This study was based on data from 285,526 women—an enormous number—between the ages of 25 and 70 years, who are all part of the ten-nation European Prospective Investigation Into Cancer and Nutrition (EPIC) Study.

Between 1992 and 1998, the participants completed diet questionnaires designed specifically for their country. Participants also filled out lifestyle questionnaires, which included questions on other factors thought to affect breast cancer risk (e.g. use of oral contraceptives, tobacco use, physical activity, and use of hormone replacement therapy). When doing their analysis, the researchers took into account the participants age, total calorie intake, fat consumption, and alcohol consumption.

In order to compare the dietary data across the participating centers, the researchers calibrated this information using a 24-hour diet recall method common to all centers. The researchers followed the participants until 2002.

The Findings

During the follow-up period, 3,659 (1.3%) of the women were diagnosed with invasive breast cancer. However, the researchers observed no significant associations between fruit or vegetable intake and the incidence of breast cancer. They examined this relationship from several different angles—total fruit and vegetable consumption, fruit consumption, vegetable consumption classified into six different subgroups, and country—and found the same results.

How Does This Affect You?

This study suggests that fruits and vegetables, despite their many other benefits, may not protect against breast cancer.

Although this may be discouraging news, it is by no means a reason to stop striving for a diet abundant in fruits and vegetables. After all, there is a wealth of evidence linking fruits and vegetables to other health benefits, including a decreased risk of heart disease , hypertension , and type 2 diabetes . Furthermore, because they are low in calories and high in fiber, fruits and vegetables are among the few types of food that you can eat in excess and not worry about gaining weight.

The authors of the study also note that before a beneficial effect can be completely ruled out, there needs to be additional research looking at the relationship between specific nutrients in fruits and vegetables and breast cancer. For example, some studies have shown that lycopene, a nutrient found mainly in tomatoes, reduces the risk of prostate cancer.

As with any cancer, there are many factors that play a role in the development of breast cancer, some of which are not yet known. The best way to lower your risk of dying from best cancer is through regular screenings. The American Cancer Society recommends that women 20 or older have a clinical breast exam at least every three years and, starting at age 40, yearly mammograms and clinical breast exams. Some women may have a higher risk of developing breast cancer and need more frequent screening; you should discuss these recommendations with your doctor to determine whether they are appropriate for you.