Western Diet May Increase Breast Cancer Risk

< Jul. 11, 2007 > -- A study of older Chinese women suggests that a move toward a Western-style diet - heavy on meat and sugary foods - boosts breast cancer risk.

According to researchers who conducted the analysis at Fox Chase Cancer Center in Philadelphia, Harvard University, Shanghai Cancer Institute, and Vanderbilt University, the findings mark the first time a specific association between a western diet and breast cancer has been identified in Asian women.

Postmenopausal Chinese women who ate a diet that included red meat, starches, and sweets were twice as likely to develop breast cancer than those who ate the traditional vegetable-soy-fish diet, according to a study in the journal Cancer Epidemiology, Biomarkers & Prevention.

Dietary Patterns Changing in Asian Women

“The issue [of diet] is of particular relevance to women in Asia, for whom breast cancer rates are traditionally low but increasing steadily in recent years,” explains Marilyn Tseng, Ph.D., an associate member in the population science division at Fox Chase Cancer Center in Philadelphia.

The increase in breast cancer risk has been attributed to environmental factors, possibly the incorporation of Western dietary pattern foods into traditional dietary habits as a part of broader, societal socioeconomic changes. However, the association of dietary patterns with breast cancer risk has not been studied previously in Asian women.

“The Shanghai data gave us a unique look at a population of Chinese women who were beginning to adopt more western-style eating habits,” says Dr. Tseng. “We found an association between a western-style diet and breast cancer was pronounced in postmenopausal women, especially heavier women with estrogen receptor-positive tumors.”

Breast cancers marked by the excessive production of estrogen receptors (ER-positive breast cancers) form the majority of breast cancers and are often associated with obesity. According to Dr. Tseng, there seems to be a specific interaction between obesity and western cuisine among postmenopausal women that drives breast cancer, although the study did not offer a specific mechanism.

"Meat-Sweet," "Vegetable-Soy" Diets Studied

Eligible cases included all women 25 to 64 years of age from the Shanghai Breast Cancer Study. Each participant was newly diagnosed with breast cancer. Enrollment in the study occurred from 1996 to 1998. A control group, selected from the Shanghai Resident Registry of permanent residents in urban Shanghai, was used for comparison.

The study is the latest set of findings derived from the Shanghai Breast Cancer Study, conducted in the 1990s by Dr. Wei Zheng and colleagues at Vanderbilt University.

Through in-person interviews with the Shanghai study participants and residents of Shanghai, researchers established the existence of two primary dietary patterns - the “meat-sweet” diet and a “vegetable-soy” diet.

The “meat-sweet” diet includes various meats - primarily pork but also poultry, organ meats, beef, lamb, saltwater fish, shrimp and other shellfish, as well as candy, dessert, bread, and milk. The “vegetable-soy” pattern is associated with different vegetables, soy-based products, and freshwater fish.

"Meat-Sweet," Obesity May Interact to Increase Risk

"Our study suggests the possibility that the 'meat-sweet' pattern interacts with obesity to increase breast cancer risk," Dr. Tseng says.

"Low consumption of a western dietary pattern plus successful weight control may protect against breast cancer in a traditionally low-risk Asian population that is poised to more broadly adopt foods characteristic of western societies," adds Dr. Tseng.

According to the National Cancer Institute (NCI), having a healthy diet, being physically active, and maintaining a healthy weight may help reduce cancer risk.

Always consult your physician for more information.

More on Nutrition and Cancer

The scientific community is continually studying the role of diet in the development of cancer. Many results are preliminary, but more is learned daily.

Researchers are discovering that intake of fruits, vegetables, and cereal grains may interfere with the process of developing cancer of the oral cavity, larynx, esophagus, stomach, colon, lung, prostate, and rectum.

In addition to reducing the risk of developing cancer, the risk of developing heart disease, hypertension, obesity, diabetes, and other chronic diseases might also be prevented by eating more fruits and vegetables.

There is also evidence that total fat intake of greater than 30 percent of total calories can increase the risk of developing some cancers. This is especially true when total fat intake includes saturated fat and possibly polyunsaturated fat.

The Food Guide Pyramid, Dietary Guidelines for Americans, and 5 A Day for Better Health Campaign are good sources for nutritional information that incorporate current research findings.

Preliminary evidence suggests that some components of food may play a role in decreasing the risk of developing cancer, including phytochemicals, antioxidants, and omega-3 fatty acids.

Phytochemicals are plant chemicals that protect against bacteria, viruses, and fungi. Eating large amounts of brightly colored fruits and vegetables (yellow, orange, red, green, white, blue, purple), whole grains/cereals, and beans containing phytochemicals may decrease the risk of developing certain cancers as well as diabetes, hypertension, and heart disease.

The action of phytochemicals varies by color and type of the food. They may act as antioxidants or nutrient protectors, or prevent carcinogens (cancer causing agents) from forming.

Antioxidants are substances that inhibit the oxidation process and act as protective agents. They protect the body from the damaging effects of free radicals (by-products of the body’s normal chemical processes). Free radicals attack healthy cells, which changes their DNA, allowing tumors to grow.

Research is underway to investigate the role of antioxidants in decreasing the risk of developing cancer.

Researchers are also studying the effects omega-3 fatty acids have on delaying or reducing tumor development in breast and prostate cancer. Since our bodies cannot make omega-3 fatty acids, we must get them from food or supplements. Fish such as mackerel and salmon are good sources of omega-3 fatty acids.

Always consult your physician for more information.