Soy and Isoflavones

Unsafe?... Depends on the Dose

A recent article has people concerned about nutritional supplements containing soy isoflavones. Dr. Steven Clinton from Ohio State University claims that adding soy foods to one's diet is a good way to reduce risk for cardiovascular disease and cancer, but warns that soy supplements, some of which contain extremely high doses of isoflavones such as genistein and daidzin may actually stimulate cancer growth.

Really?

Aside from assuring that he would make the evening news, Dr. Clinton has very little evidence for his hand-wringing. Exposing immune cells to high concentrations of isoflavones caused a marked alteration of cell function, but it's unscientific and unreasonable to conclude that taking soy supplements causes cancer. On the other hand, you have to admit that there are high-potency isoflavone products on the market and that people often believe that if a little is good, a lot must be better.

What's the best course of action?

1. The Asian diet is believed by most experts to be primarily responsible for their lower incidence of heart disease, prostate and breast cancer.
2. Abundant evidence exists to correlate isoflavone intake to reduced risk for these disorders.
   Reference: Wiseman H. The therapeutic potential of phytoestrogens.
   Expert Opin Investig Drugs. 2000 Aug;9(8):1829-40.
3. Based on soy food consumption in Japan, typical daily isoflavone intake has been estimated at approximately 50 mg/person.
   Reference: American Journal of Clinical Nutrition 1995; 62:645-9.
4. This isoflavone level can be obtained from two and a half servings of soy foods per day; such as 3 cups of soy milk or a cup and a half of tofu.
5. Question. Will Americans consume this amount of soy foods every day?
   Answer. No way.
6. Should Americans eat this amount of soy foods every day?
   Answer: Maybe not (see the Soy Debate: Part I)
7. So how do we help provide the benefits of soy isoflavones in a safe and efficient way?
   Answer: Nature suggests a reasonable dose target for supplementation, being 10 to 50 mg per day. In other words, the amount derived from a natural foods diet rich in soy and other legumes.
8. One more point. Some of the high-potency isoflavone products no longer resemble soybeans at all, in that their isoflavone content is skewed by the extraction process. Be sure to select a compound that is carefully extracted to assure that the natural profiles and ratios of isoflavones and other natural compounds are maintained as they are found in the soybean.

IMPORTANT NOTE. This fact sheet refers to features and benefits associated with isoflavones, and controversial points are supported by references to published biomedical literature. Nevertheless, I fully acknowledge that there may be competent scientists who disagree with this position, or who may feel that the cited references provide inadequate scientific support. Such is the case in any rapidly evolving field of research.

We therefore encourage readers to consult with their health care professional or scientific expert. We welcome comments from other scientists and look forward to developing consensus on these important issues.

Spilling the Beans on Soy

by Heidi Sopinka

What could be a more eco-righteous symbol of the hippie vegetarian movement than a block of tofu? As it turns out, the gentle bean has become somewhat of a blood crop in South America. A recent article in The Daily Telegraph uncovered that land-rights activists are risking death, while vast swaths of rainforest are being felled to provide land for the booming soy industry in Brazil (now surpassing the United States as the top soy exporter in the world). With the added issues of widespread genetically modified and pesticide-laden crops, along with the documented dangers of eating too much unfermented soy, just how green is the soy bean?

27,200

Amount in square kilometres (an area about the size of Belgium) of Amazon rainforest cleared for monoculture soybean farming between August, 2003, and August, 2004. Three-quarters of this destruction was illegal.

75 to 89

Percentage of soybeans grown in North America that are genetically modified. Even if you are actively avoiding GM foods, GM soy is present in approximately 60 per cent of processed foods - usually as filler or oil. Neither Canada nor the United States requires any safety testing on GM food products, despite findings of toxicity and cancer-promoting properties.

115

Celsius temperature to which soy beans are heated in the production of commercial soy milk in an attempt to remove trypsin inhibitors (they interfere with protein digestion and have been linked to pancreatic disorders), but the phytate content remains largely intact. (Phytates block the absorption of essential minerals such as calcium, magnesium, iron and especially zinc in the intestinal tract.)

5

The equivalent number of birth-control pills a day that babies fed exclusively on soy formula would be consuming, according to a British toxicologist’s calculations. (Components of soy called isoflavones produce estrogen-like effects in the body, and as a result are sometimes called phytoestrogens.) Thirty to 40 per cent of babies in the United States are fed soy formula.

Bottom Line

From fast food to pet food, soy is wall-to-wall in our edible products. And while organic fermented soy can be good in moderation, eating a tofu burger and washing it down with a glass of soy milk on a daily basis could prove hazardous to your health. Although the lauded Asian diet has incorporated soy for centuries, it has never included the large amounts of unfermented and heavily processed soy products consumed in North America that have toxicologists worried. When seeking out soy, look for products that are labelled “organic soy,” which means they are genetically unaltered and pesticide-free. Fermented soy products, including miso, tempeh and tamari sauce, are healthy choices (the fermentation process removes the phytates, trypsin inhibitors and hemagglutinins, which can cause clots). If only the hippies had known that soy was going to wind up a Frankenfood blood crop - chances are they would’ve just stuck to the wheatgrass.

Sources:

Health Canada, U.K. Medical Research Council, U.S. Food and Drug Administration, Worldwatch Institute, World Wildlife Fund