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The Latest on Soy: Panacea or Poison?

In soyfoods, Trends on September 15, 2010 at 9:51 PM

Soyfoods, such as tofu, soymilk, edamame, miso, and tempeh, have long been a diet staple in Asia.  They have been linked to a reduced risk of prostate and breast cancers, and lower rates of osteopororis and heart disease.  Sounds like a perfect “functional” food  to help heal what ails us, doesn’t it?  Well, unfortunately for us “Westerners”, who were not born and raised eating foods comprised of soy protein, such foods do not seem to have the same dramatic impact on our health.  Back in the 1990’s, the medical community was convinced that soy was a wonder food, such that, in 1998, the FDA approved a food claim of “25 grams of soy protein a day may reduce your risk of heart disease”.  No so fast my friends…  Twelve years later, research has shown that is not the soy itself that helps to lower our cholesterol.  There have also been questions about soy raising one’s risk for breast and prostate cancers,  since soy isoflavones can behave like estrogens and encourage growth of hormone-sensitive cancers. 

The ultimate effects of soy will vary from person to person.  Less processed, more natural soy products, such as those mentioned above, are low fat, high protein choices that fit nicely into a healthy eating plan.  On the other hand, highly processed soy derivatives, such as most “veggie” burgers and meat substitutes, tend to be of little nutritional value and loaded in sodium.  Most of the commercial soy products marketed today are overly processed—having stripped away the natural nutrients, and maybe added in some fortification.   I am not particularly interested in serving up some “texturized soy protein” or “soy protein isolate” at my next meal or snack…  That’s right— I’m not high on the LUNA protein bar.  Sorry, ladies ;-(

I am going to run down the latest news regarding soy products, to help you determine whether or not you should include soy in your diet:

1.  Heart disease:  soy’s heart-health benefits have largely been attributed to its ability to lower cholesterol.  As mentioned above, soy had once been thought to significantly lower blood cholesterol levels.  Since then, research results have shown a less significant effect.  Still, soy isoflavones may act as antioxidants and have other beneficial effects on blood vessels and the heart.  Soy foods, such as edamame (green soy beans) and soy nuts, are good sources of fiber and heart-healthy polyunsaturated fats.  The greatest cholesterol-lowering effect is more likely to occur when you replace high fat cheeses, milk, and meat with veggie cheese, soymilk, and tofu.  Choosing low-fat dairy cheese and skim milk, while consuming lean meat in small portions, will also provide the same benefit.

2.  Breast Cancer:  does soy help prevent breast cancer or promote it?  The research has yielded conflicting and inconsistent findings… One theory is that isoflavones, such as genistein, bind to estrogen receptors in the breast, inhibiting natural estrogen action, and thus reducing the risk of breast cancer.  Another outcome suggested by research is that soy’s estrogen properties may increase the growth of breast cancer cells.  Well, Asian women have lower rates of breast cancer.  They start consuming soy in childhood, prior to puberty.  Could early consumption of soy be protective against breast cancer later in life?  Could it be that soy’s effect comes from when a women BEGINS consuming soy? This is the burning question that needs to find an answer…

For women who have or have had breast cancer, soy’s effects are even less clear.  At this point, it is probably best for such women to either steer clear of soy foods all together, or to limit consumption to only a few servings per week.   This would be true for women with or without hormone-dependent breast cancer.  You definitely want to avoid any concentrated form of soy isoflavones from pills and powder supplements.

3.  Prostate Cancer:  men who eat more soy have a lower risk of prostate cancer, according to some, but not all, research studies.  Other studies suggest that soy may benefit men WITH prostate cancer or those at high risk.   Again, this has to do with the potentiating effects of soy on hormonally-charged cancer.  Men most certainly can eat less processed soy foods, such as tofu, edamame, and soymilk,  but choose only whey protein powders instead of soy-based ones, should you use a powder supplement for exercise training purposes.

4.  Osteoporosis:  soy isoflavones may stimulate bone formation and also reduce bone loss, possibly due to their estrogen-like activity.  But some studies have not found benefits, possibly because they have used different soy products and doses…  Instead of hoping for the best with soy products, the surest way to reduce bone loss is to consume adequate calcium and vitamin D, either from food or supplements, and get plenty of weight-bearing exercise in the form of walking and strength-training.

5.  Menopause:  Most studies on menopause have used soy supplements, and as usual, there have been mixed reviews on soy’s ability to impact hot flashes and other menopausal symptoms.   Because supplements concentrate the hormone-like soy isoflavones, they may have different effects in the body than whole soy foods.  The long-term safety of supplements is largely untested, and I would not recommend them for anyone, especially women with or at high risk for breast or endometrial cancer.

6.  Thyroid disease:  it has recently been found that soy isoflavones may interfere in the absorption of thyroid hormone replacement medication.  Therefore, it is suggested you not consume soy products within four hours of taking thyroid medication, but it is safe to consume soy products in moderation as part of an overall healthy diet.

Guidelines for prudent soy intake:

-eat soy foods in moderation, if you like them, particularly those in whole form or minimally processed (edamame, tofu, soymilk, tempeh, soy nuts, soynut butter)

-whole soy foods provide good quality protein, healthy fats, fiber, and other nutrients such as magnesium, boron, and calcium

-replacing high fat meat and cheese a few times per week with lower-fat, lower-calorie soy protein is smart for heart health and weight control

-don’t be fooled by most packaged soy products, which tend to be high in sodium and calories, and often require fortification to gain back nutrients. (i.e. a handful of soy nuts is a better snack than that soy protein bar)

My favorite soyfood is green soybeans, also known as, edamame—tossed into rice dishes, salads, soups, or eaten by the handful.   They can often be found in the freezer section of your local grocer.  Try some in your next recipe and let me know what you think…

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