A Four-Part Series by Susan Silberstein, PhD, Center for Advancement in Cancer Education
Previously in this series, we have discussed “diet and demographics,” “the bad news,” and “the good news.” Continuing with the empowering aspects of dietary change, let us now highlight certain aspects of the traditional Asian diet that are particularly protective against breast cancer. Certainly, a heavily plant-based diet of vegetables and grains with little or no meat, dairy or saturated fat is protective in the ways we discussed earlier in this series. In addition, let us examine four specific staples of the Asian diet.
First, consider green tea, from the plant Camellia Sinensis. Green tea contains antioxidant compounds called catechins, polyphenols and EGCG, which fight cancer and are highly stimulatory to the immune system. In a study published in 1994 (Cancer Letters), green tea was shown to inhibit breast cancer growth. Two groups of female rats were pre-treated with carcinogenic chemicals that caused breast cancer. One group was also given green tea. After 36 weeks, the number of survivors in the green tea group was significantly higher (94%) than in the non-green tea group (33%). At week 18, when all the animals were still alive, the average tumor size was much smaller in the green tea group. Several studies have also featured human breast cancer-related green tea research.
Reduced risk of breast cancer among Asian populations as compared with western populations is often attributed in part to the prevalence of soy in the diet. Soy contains phytoestrogens, or weak plant sources of estrogen, known as isoflavones. One major isoflavone is genistein, which interferes with the tumor’s ability to develop its own blood supply. Genistein has been shown to inhibit the growth of human breast cancer cells (Cell Growth & Differentiation, 1996). Research has demonstrated that soy isoflavones can block the effect of the more dangerous estrogens on breast tissue. In laboratory and animal experiments, soy has inhibited growth of both estrogen receptor positive and estrogen receptor negative breast cancer cells. In a study of pre- and post-menopausal women, 45 mg of soy isoflavones daily decreased circulating levels of estrogen, thus helping to prevent breast cancer. In research conducted at Queen Elizabeth Medical Center is Australia, women with the least amount of phytoestrogens were three times more likely to have breast cancer than those who had the most (Lancet, 1997).
A 1996 study showed frequency of soy consumption was more than twice as high among Asian American women born in Asia (62 times/year) as among Asian American women born in the US (30 times/year). New research on over 1500 Asian American women showed that high consumption of soy-based foods during childhood could reduce the risk of breast cancer later in life by 58 percent (US National Cancer Institute, 2006).
Because of its estrogen content, some oncologists restrict patients from consuming all soy products. However, soy can be extremely beneficial if the type and quality of the soy are clearly defined. Fermented soy as consumed in Asia (for example, tempeh and miso) is generally much safer and more effective than modern processed soy consumed in the west.
Another key component of the Asian diet is sea vegetables like kelp, nori, and wakame. Sea vegetables are valuable in the fight against breast cancer in three ways. First, they contain special fibers which can bind up free form estrogen before it can stimulate cancer cell growth. Second, seaweed is rich in omega-3 fatty acids, which inhibit breast cancer and stimulate the immune system. Third, sea veggies contain the mineral iodine — and breast tissue is a sponge for iodine. Iodine deficiency increases the sensitivity of breast tissue to estrogen, leading to fibrocystic breast disease and breast cancer — both of which tend to resolve with iodine replacement therapy. (Journal of the American Med. Assoc. 1967, Can. Journal of Surgery, 1993).
Finally, let us mention the shitake, a mushroom has been a traditional food in Japanese and other Asian cultures for centuries. Shitakes contain a compound called lentinen, which can increase T-cell counts, especially the T-helper counts and Natural Killer cell counts — all key players in the immune response to cancer. Shitakes also stimulate interferon and interleukin production, which provides a woman her own immunotherapy in biologically appropriate doses.
Sadly, as Asian women abandon their traditional oriental dietary patterns in favor of western ways, their rates of breast cancer, like all killer diseases, are rising. Fortunately, however, returning to traditional eating habits can help not only prevent the disease but also slow the progression of active breast cancer. According to the Journal of the National Cancer Institute (1993), poor dietary habits are strongly associated with risk for treatment failure, and dietary intervention could be a valuable approach for improving treatment outcome.