| The AHA panel nonetheless spoke quite positively about soy as a food, noting that “many soy products should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat.” However, they advised against use of soy isoflavone supplements.
CANCER
When evaluating the possible relationship of soy and cancer, it is best to make two key distinctions. First, possible preventive effects for people who have never had cancer should be distinguished from potential effects on people who have (or previously had) cancer. Second, it is probably best to discuss each type of cancer separately rather than make across-the-board generalizations about all cancers. Breast cancer may differ in significant ways from prostate or colon cancer, in terms of prevention and the dietary management of diagnosed cancers.
PROSTATE CANCER PREVENTION
Bottom line: There is strong evidence that soy helps prevent prostate cancer.
An informed consensus has emerged among the scientists who closely study the issue – soy appears to be protective against prostate cancer. A 2009 meta-analysis5 by Yan and Spitznagel, published in the American Journal of Clinical Nutrition, concluded that consumption of soy foods was associated with a lowered risk for prostate cancer. Lin Yan, PhD, the study’s lead author and a research nutritionist for the United States Department of Agriculture in North Dakota, stated in a recent lecture that, based on current research and knowledge of traditional patterns of use in Asian societies, up to three servings per day of soy foods is beneficial.
PROSTATE CANCER TREATMENT
Bottom line: There is preliminary evidence that soy may play a supportive role in the treatment of prostate cancer, as part of a comprehensive lifestyle changes program.
Dean Ornish, MD, the cardiologist and University of California, San Francisco Medical School professor best known for his groundbreaking research proving that heart disease could be reversed6,7 through a combination of diet, exercise, stress management, and social support, has been deeply involved in prostate cancer research in recent years. Dr. Ornish’s group has given early-stage prostate cancer patients a whole foods, low-fat, soy-supplemented vegan diet consisting predominantly of fruits, vegetables, whole grains (complex carbohydrates), legumes and soy products (1 daily serving of tofu plus a fortified soy protein powdered beverage), low in simple carbohydrates and with approximately 10% of calories from fat.
The results? After one year, none of the men in the experimental group needed to undergo conventional treatments compared to six in the control group. Prostate Specific Antigen (PSA) levels decreased 4% in the experimental group compared to a 6% increase in the control group, and prostate cancer cell growth was inhibited almost eight times as much in the experimental group compared to the control group.8 Other promising but preliminary findings in this ongoing prostate cancer research include positive changes in prostate gene expression9 and increased telomerase activity.10
Ornish noted in a recent talk that research focused on dietary and lifestyle approaches for prostate cancer is possible because many men with slow growing, less aggressive prostate cancers choose not to pursue treatments such as surgery, radiation or chemotherapy. This is not true for breast cancer. The number of American women with breast cancer who elect not to undergo aggressive treatment is so small that research on dietary and lifestyle approaches (in the absence of surgery, radiation or chemotherapy) is currently impossible.
For further information on Dr. Ornish’s work on prostate cancer and heart disease, visit the Preventive Medicine Institute website at www.pmri.org. |
