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Soy Connection by Yvona Fast
Today soy is known as an inexpensive source of protein. Both the Food Guide Pyramid and Nutrition and Your Health: Dietary Guidelines for Americans, fifth ed., list soy foods as a way to meet dietary guidelines. A one-cup (8 oz.) serving of tofu, for example, is listed as a serving suggestion in the meat and beans Group. Soy's health claims have been widely publicized by organizations such as the United Soybean Board (USB) and the health food industry. This has led to a dramatic rise in popularity. For example, American sales of soy milk soared from $2 million in 1980 to $300 million by 2000. (Lifestyle magazine, Autumn 2000). Proponents claim that soy lowers the risk of cancer, osteoporosis, and other chronic diseases (Drug Metabolism Drug Interactions;17 2000 (1-4):261-89). Other researchers, however, urge us to proceed with caution. Daniel Doerge and Daniel Sheehan, two research scientists and soy experts with the Food and Drug Administration (FDA), are among those who challenge the presumed benefits of soy (ABC's 20/20, June 9, 2000; see abcnews.go.com/onair/2020/2020_000609_soy_feature.html. Some of the concerns raised include soy's effect on brain function in adults, development in infants, and increased risk of breast cancer. Of particular interest are the estrogen-like isoflavonoid substances found in soy. These plant compounds mimic estrogen, a female hormone that has naturally fluctuating levels during a woman's life. Cultural observers have noted that Asian women suffer less menopausal distress than American women, and attribute this fact to the diet rich in soy. As a result, phytoestrogens from soy have been used to reduce menopausal symptoms and as a natural alternative to hormone replacement therapy, or HRT, (Obstetrics Gynecology 99, No. 3 Mar. 2202: 389-94). Indeed, intake of certain soy products does alleviate the severity of hot flashes (Climacteric 2, No. 1 Mar. 1999: 6-12). Whether soy foods can provide the same types of benefits as HRT, however, is yet to be determined. Unfortunately, like HRT, these chemicals can also increase the risk of certain estrogen-dependent cancers, such as breast or ovarian cancer, because they speed up the division of cancer cells that depend on estrogen for their growth (Cancer Research 61, No. 13 July 1, 2001: 5045-50 ; Advances in Experimental Medicine and Biology 492 2001: 19-28). One hundred grams of soy, or two glasses of soy milk a day, has the estrogen simulation effect of a contraceptive pill and can cause changes in a healthy woman's menstrual cycle. Another concern is calcium, which is important for bone health. Some say soy milks have less than a fifth of the calcium of dairy milk (see comparison of various milks, at www.tofu.com). New research is questioning the purported health benefits of soy in adults and raising concerns about adverse effects in children (Environmental Health Perspectives 110, No. 6 June 2002: A294-6). More than one fourth of infant formulas marketed in the U.S. are soy-based, yet it's not known what effect these chemicals have on normal development. Soy formula provides a hormone level at least 240 times higher than breast milk. If soy products supply sufficient hormones to counteract their natural decline in older women, what are they doing to newborn babies fed soy formula? On the other hand, dietary soy intake has been shown to have beneficial effects on cardiovascular health (Journal of Nutrition 131, No. 4 April 2001: 1202-6; Journal of Nutrition 132, No. 2 Feb. 2002: 276-82). There's no evidence, however, that it's the isoflavones in soy that account for these cardiovascular benefits (Journal of Nutrition 2002 Mar;132(3):566S-569S). The only authorized soy health claim to date is that "25 grams of soy protein a day, as part of diet low in saturated fat and cholesterol, may reduce the risk of heart disease" (U.S. FDA, 2000). Here are some Web sites to help you understand and use soy products.
Yvona Fast writes on health issues from Lake Clear, New York.
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