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Are You Getting Enough Soy Isoflavones To Protect Your Health?
James Meschino DC, MS, ROHP
World-wide statistics indicate that Japan enjoys a 75% decreased incidence of breast cancer and an 80% decreased incidence of prostate cancer compared to the United States, Canada and many other developed countries. Many studies suggest that much of the variation in breast and prostate cancer incidence between Asian countries and modern Western countries can be explained by the higher consumption of soy foods and soy isoflavones, which are staples of the Japanese and Asian diets. As well, a high ingestion of soy foods is also associated with lower cholesterol levels and a decreased incidence of cardiovascular disease.
The question that many people ask is, “how much soy should I consume and how many milligrams of soy isoflavones should I derive from these foods to get the levels of intake associated with cutting my risk of cancer and heart disease?”
To help answer this question a recent research paper published by M. Messina and fellow researchers looked at soy intake surveys from Japan, China, Hong, Kong and Singapore.
These researchers showed that the traditional Japanese diet contains approximately 90 grams of soy food per day, which yields 6-11 grams of soy protein and 25-50 mg of soy isoflavones. A number of investigators have suggested that this is the level of intake that may appears to be prudent to reduce risk of certain degenerative diseases, such as cancer, heart disease and osteoporosis. The daily average of soy isoflavone intake across the entire Japanese population is reported to be approximately 35 mg per day.
Based on reports such as these, I have routinely recommended to both my male and female adult patients, who are free from reproductive disease, soy allergies or sensitivities, that they ingest at least 35-50 mg of soy isoflavones per day from any combination of soy foods, functional foods (e.g. soy protein shakes) and/or supplements, as a means to support their health and help prevent a number of degenerative diseases.
To help control hot flashes and other symptoms of menopause, and to slow bone demineralization associated with menopause, some studies indicate that 50-100 mg of isoflavones are beneficial for those purposes. Thus, women over 50 should seek the higher levels of soy isoflavone intake via food and supplements, in my opinion.
The Chart below indicates the amount of isoflavones available from standard serving sizes of a wider variety of soy products:
Soy Isoflavone Content Of Foods
|Isoflavone content (mg)
|Soy Milk unfortified
|1 cup (8 oz)
|Soy Milk fortified
|1 cup (8 oz)
|Soybeans, green cooked (e.g. edamame)
|Soybeans, black cooked
|Soybeans, yellow cooked
|Soy protein isolate powder
Many functional foods, such as soy protein shake mixes, soy bars (e.g., chocolate bars with soy), soy sausages, hotdogs, and soy cheeses, list the protein and isoflavone content on the label. It is not uncommon for a 3.3 ounce soy hotdog to contain 15 mg of isoflavones, or for a 3.3 ounce soy burger to contain 15-25 gm of isoflavones. Some soy protein bars contain up to 60 mg of isoflavones in two ounces. Soy cheeses often contain 8 mg of isoflavones in 3.3 ounces.
Soy foods are unique in that they are the only nutritionally relevant naturally-occurring “food” source of isoflavones. People around the world who rely on soy foods as a dietary staple have significantly lower incidence of reproductive organ cancers and other health problems. Investigative research has demonstrated that soy isoflavones and other constituents of soy foods exhibit numerous anti-cancer properties and several clinical trials have demonstrated the ability of soy isoflavone supplementation to slow the growth of breast and prostate cancer.
For this reason I recommend that most adults consume at least 35-50 mg of soy isoflavones per day for general health promotion purposes. For women combating menopausal symptoms, or wanting to boost their bone support after age 50, I suggest taking a customized soy-containing supplement. The same is true for men over 40 years of age. Men need extra prostate protection at this stage in life, and a customized soy-containing supplement is extremely beneficial in this regard.
The bottom line is simply to refer to the table above as a method to plan your soy and soy isoflavone strategy from food, in an attempt of acquire an average of 35 mg of soy isoflavones per day. In addition, women over 50, and men over 40, should strongly consider adding a soy-containing supplement to their overall wellness and disease prevention game plan.
- Sartippour MR, Rao JY, Apple S et al. A pilot clinical study of short-term isoflavone supplements in breast cancer patients. 2004. Nutr and Cancer, 49;1: 59-65
- Messina, M: Legumes and Soybeans: overview of their nutritional profiles and health effects. Am J Clin Nutr 1999 Vol 70 (suppl); 439-50
- Messina M, Nagata C, Wu AH. Estimated Asian Adult Soy Protein and Isoflavone Intakes. Nutr and Cancer; 55 (1):1-12. 2006
- Hussain M, Banerjee M, Sarkar FH et al. Soy isoflavones in the treatment of prostate cancer. 2003. Nutr and Cancer, 42;2: 111-117
- Molteni A, Brizio-Molteni L, and Persky V. In vitro hormonal effects of soybean isoflavones. 1995. J Nutr, 125: suppl:751S-756S
- Chen X and Anderson Isoflavones inhibit proliferation of ovarian cancer cells in vitro via an estrogen receptor-dependent pathway. 2001. Nutr and Cancer, 41;1&2: 156-171
- Constantinou AI, Lantvit D, Hawthorne M et al. Chemopreventive effects of soy protein and purified isoflavones on DMBA-induced mammary tumors in female Sprague-Dawley rats. 2001. Nutr and Cancer, 41;1&2: 75-81