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(HealthNewsDigest.com) – Soybeans, edamame, and all things made of soy were once the darlings of the food industry touted as the cure-all for heart disease, breast cancer, hot flashes and osteoporosis. As with many areas of evolving research the promise did not measure up to the hype. Does that mean we should stop eating soybeans and soy foods? Not at all. Soybeans and many of the foods made from soy are excellent – just not the health miracle once promised.
Why are soybeans different from other beans?
Soybeans are unique among all plant foods because of their protein content and quality, equal to that found in milk, meat or eggs. The soybean is 40% protein, 20% oil, 35% carbohydrate and 5% minerals and other active compounds. Most important among these are isoflavones, powerful estrogen-like phytochemicals which have been linked to reducing the risk for breast cancer and relieving symptoms of menopause.
If soybeans and soyfoods are so nutritious why don’t they offer more disease protection?
Soybeans offer a great example of the wholefood principle, plus the importance of eating well throughout life. The early promising data about the ability of soy to protect against heart disease and cancer were drawn from studies of traditional Asian diets that were rich in soy, but also rich in vegetables, low in fat, and used smaller portions. In addition, the people studied ate this way throughout their lives.
In contrast, American diets are far more energy dense, contain more food, more fat, and more sugar. When soy was added to this eating pattern the disease protection potential was much smaller.
The Asian diets also contained more soybeans, tofu, tempeh, miso, soybean oil and soy sauce. The American diets contained “second generation” soy products, foods that are soy-based, made from soy flour, soy protein, or soy protein isolate, like veggie burgers, meat substitutes, and soy cereals. Depending on the processing, the amount of isoflavones can vary dramatically. In a free-living population it is hard to get an accurate value on the amount of isoflavones eaten from soyfoods making it is almost impossible to measure the health benefits.
You should know about the isoflavone level in different soy foods:
High levels – edamame, soybeans, soynuts, tempeh, soymilk, soy yogurt and tofu.
Moderate levels — soy cereal, soy flour, and soynut butter.
Low levels – frozen soy desserts, soy ice cream and meat substitutes.
The actual level of isoflavones in a food varies by brand and the degree of processing the food undergoes.
Does soy offer protection against heart disease?
Yes. Soy can help to reduce total cholesterol, bad LDL cholesterol and triglycerides and it helps reduce inflammation which can lead to plaque buildup in the arteries. Research showed the protection was more likely when whole soyfoods, like soynuts, were eaten regularly, rather than from processed soyfoods or soy supplements. Eating any type of soyfood will reduce the amount of saturated fat and cholesterol in your diet if you eat them instead of meat, milk, or cheese.
Does soy protect against or cause breast cancer?
Certain groups of women who eat a lot of soy had a lower risk of breast cancer. But, these women ate soyfoods since they were teenagers and also ate a vegetable-based Asian diet. So, we are not sure if it was the soy or the diet — or the two combined. Starting to eat soyfoods as an adult, in the hope of protecting again breast cancer may not work.
There is also concern that increased consumption of the estrogen-like isoflavones found in soy could promote the growth of precancerous or malignant cells. This could be especially important for women who are at high risk for developing breast cancer or those who have estrogen-sensitive breast cancer. But, another long term study has found no effect from isoflavones on cancer risk.
The American Cancer Society suggests moderation. It recommends that breast cancer survivors eat moderate amounts of soy foods and not use isoflavone supplements. For everyone else, using some soyfoods is fine; overdoing it in the hope of some perceived health benefit is probably not wise until we learn more.
You should know that a moderate amount of soyfood equals: 1 cup of soymilk, a few ounces of tofu, or a handful of soynuts.
This is what the research evidence says about soy and the reduction of:
Hot flashes: modestly reduces the number of episodes, but effect varies between women
Vaginal dryness: no effect
Dementia: results to date are not promising and some studies show a slight increase with high consumption
Normal aging: could have promise but much more research is needed
Osteoporosis: the effects are modest and the spine appears to benefit more than the hip
Prostate cancer: may protect against the progress of dormant cancer, with the most protection seen in men over 60, but soy offers no benefit against advanced cancer.
Soy, by itself, is not a magic food. But, it is great example of the wisdom of eating good foods to achieve a positive effect on your health.
© NRH Nutrition Consultants, Inc.
Jo-Ann Heslin, MA, RD, CDN is a registered dietitian and the author of the nutrition counter series for Pocket Books with 12 current titles and sales in excess of 7 million books. The books are widely available at your local or on-line bookseller.
Current titles include:
The Complete Food Counter, 3rd ed., 2009
The Fat Counter, 7th ed., 2009
The Healthy Wholefoods Counter, 2008
The Cholesterol Counter, 7th Ed., 2008
The Diabetes Carbohydrate and Calorie Counter, 3rd Ed., 2007
The Calorie Counter, 4th Ed., 2007
For more information on Jo-Ann and her books, go to The Nutrition Experts
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