A Diet High in Fruits and Vegetables May Reduce Risk of Breast Cancer, A New Study Finds
|FREMONT, CA (November 7, 2013) — A new study addressing patterns of diet and breast cancer has found that women whose diets are primarily plant-based, consisting mostly of fruits and vegetables, have significantly lower risk of developing breast cancer, while women who consume a diet high in wine, salad and low-fat dressing may have increased risk.
The study was led by researchers from the Cancer Prevention Institute of California (CPIC) and Columbia University who worked with information obtained from thousands of women to identify a correlation between dietary patterns and breast cancer.
While a lowered risk for breast cancer was observed in the plant-based diet group as a whole, of particular note were the women who reported consuming the highest amounts of fruits and vegetables. The researchers found this group to be 35 percent less likely to develop estrogen receptor-negative (ER-) breast cancer than those who reported eating the fewest fruits and vegetables.
“The finding that women who are at high risk for ER- breast cancer can reduce their risk by consuming a diet rich in fruits and vegetables is very encouraging. It provides a simple and important preventative measure for women to take, and one likely to reduce the risk of other major chronic diseases as well,” said Pamela Horn-Ross, Ph.D., research scientist at CPIC.
“The diet does not have to be vegetarian to make a difference,” Horn-Ross noted. “What we found is that the more fruits and vegetables consumed in the overall diet, the greater the benefit.” But she noted that even those consuming the greatest amounts of fruits and vegetables also consumed meat, chicken, fish, and grain-based foods to some degree.
The researchers observed that women who consumed larger amounts of salad, fish, wine, and coffee or tea had an increased risk of developing estrogen receptor-positive (ER+) breast cancer. “While alcohol consumption accounts for some of this increased risk, it does not explain it entirely,” said Lilli Link, MD, MS, a nutrition specialist in private practice in New York, formerly affiliated with Columbia University.
“Women who consume two or more glasses of wine (or any alcoholic beverage) a day while also taking hormone therapy are at especially high risk of breast cancer, so concurrent use of hormone therapy among women consuming this dietary pattern may account for some of the risk,” Link said. “However, at this time, we don’t know what other factors may be involved.”
Published online in the American Journal of Clinical Nutrition, the study, “Dietary patterns and breast cancer risk in the California Teachers Study,” included 91,779 women from a large, diverse group that consists of active and retired teachers and school administrators in California. The participants completed a comprehensive questionnaire in 1995 regarding health status, dietary habits and lifestyle information, and were followed for 14 years thereafter.
The five major dietary patterns identified in the study included the plant-based diet consisting mostly of fruits and vegetables; a diet high in protein and fat, with meat, eggs, fried foods and high-fat condiments such as butter and mayonnaise; a diet high in convenience foods, pasta and bread products; a diet high in legumes, soy foods, rice and dark leafy vegetables; and the "salad and wine" diet, high in salads, low-fat dressing, fish, wine, and coffee and tea.
Over the 14-year period, 4,140 of the participants were diagnosed with breast cancer. The diets high in carbohydrates, in protein and fat, and in legumes and soy foods neither reduced nor increased breast cancer risk.
A number of reasons might explain why a plant-based diet might reduce breast cancer risk, the researchers suggested. Fruits and vegetables are high in fiber, which may lower breast cancer risk by reducing the concentration of estrogen in the body and keeping glucose and insulin levels stable. Fruits and vegetables are also high in antioxidants, which have been shown to inhibit growth of breast cancer cells.
The authors noted that a major strength of this study is its basis in a large, diverse group with dietary data collected prior to breast cancer diagnosis and based on a widely-used and validated food frequency questionnaire. Certain limitations were noted as well, including possible changes to dietary patterns over time and lack of distinction between cooked and raw vegetables.
In addition to Link and Horn-Ross, authors contributing to this NIH-funded study include Alison J. Canchola, MS, and Christina Clarke, Ph.D., M.P.H., of the Cancer Prevention Institute of California; Leslie Bernstein of the City of Hope; Daniel O. Stram of the University of Southern California (USC); and Giske Ursin of the University of Norway and USC.
About the Cancer Prevention Institute of California
The Cancer Prevention Institute of California (CPIC) is the nation’s premier organization dedicated to preventing cancer and to reducing its burden where it cannot yet be prevented. CPIC tracks patterns of cancer throughout the entire population and identifies those at risk for developing cancer. Its research scientists are leaders in investigating the causes of cancer in large populations to advance the development of prevention-focused interventions. CPIC’s innovative cancer prevention research and education programs, together with the work of the Stanford Cancer Institute, deliver a comprehensive arsenal for defeating cancer. For more information, visit CPIC’s official website at www.cpic.org.
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