spacekadet

Soymilk in my cereal, tempeh in my chile, and tofu in my afternoon smoothie . . .

Am I getting too much of a good thing?

Search the internet for "soy health" and you'll be bombarded with conflicting information. There's The Whole Soya Story by clinical nutritionist Kaayla Daniel (and director of the Weston A Price Foundation, a body that promotes traditional farming and the consumption of animal products). And an article in The Guardian entitled "There's no risk to humans from soya", written by a "health campaigner" with the Vegetarian & Vegan Foundation...

Where can I go for unbiased information on soy? How do soy's phytoestrogen compare to cow's oestrogen and what is their comparitive impact on health? Are soy allergies really on the rise? Should I really worry about non-organic soybeans? How do different soy products - tofu, tempeh, soymilk, soybeans, etc - compare nutritionally? What is the link between soy and increased/decreased risk of disease?

The Harvard School of Public Health provides a few seemingly unbiased answers:

• On heart disease: An updated look at the soy story, which includes several strong studies published since 2000, isn't so bullish on soy and cholesterol. According to this comprehensive update of soy research by the American Heart Association's nutrition committee, eating 50 grams of soy lowers LDL only about 3%. (12)
  
• On menopause: Soybeans are rich in phytoestrogens. In some tissues, these substances mimic the action of estrogen. So they could cool hot flashes by giving a woman an estrogen-like boost during a time of dwindling estrogen levels. Yet carefully controlled studies haven't found this to be the case, (14,15) and the AHA committee concludes that soy hasn't been shown to ease hot flashes and other symptoms of menopause.
  
• On breast cancer: Studies so far haven't provided a clear answer, with some showing a benefit and others showing no association between soy consumption and breast cancer.(12) In fact, a handful of unsettling reports suggest that concentrated supplements of soy proteins may stimulate the growth of breast cancer cells.(16,17) Large prospective studies now underway should offer better information regarding soy and breast cancer risk.
  
• On memory: wo recent trials have yielded contradictory results in this area, with one showing a benefit for soy (18) and another showing no benefit.(19) Others go further, and suggest that too much soy could lead to memory problems. Among older women of Japanese ancestry living in Hawaii, those who relied on the traditional soy-based diet were more likely to have cognitive problems than those who switched to a more Western diet.
  
• On isoflavones: There's no evidence that pills containing isoflavones extracted from soybeans offer benefits, and some studies raise concerns about harmful side effects (19).
  

A 2006 article published in Circulation by the American Heart Association provides a detailed comparison of recent studies. The results confirm the obvious: soy itself does not prevent disease. Rather, it is the replacement of foods high in saturated fat and cholesterol with alternative foods (such as soy) that improves health.

Soy products such as tofu, soy butter, soy nuts, or some soy burgers 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. Using these and other soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health.

And, yet, I still don't know what to have for dinner tonight.