Since I am not a vegetarian or
vegan I cannot say that I am a big Soy fan but, as a Professor of Nutrition I
can surely tell you that Soybeans are a wonderful source of health promoting
phytochemicals. These plant-derived
compounds have biological activities that include protecting DNA and other
cellular compounds from oxidative damage, driving the expression of health
promoting proteins, and mimicking the activity of the body’s own hormones.
Asians living in Asia have been consuming a soy-rich diet
for thousands of years and currently appear to derive many health benefits
including lower incidence of heart disease and certain cancers, and Asian women
suffer fewer menopausal symptoms. The
effects on the heart are thought to be linked to the ability of plant sterols
to lower blood cholesterol although, this may also be due to reduced
consumption of saturated fatty acids (Clin
Nutr 91:32). Soy foods also contain
phytoestrogens which are related to human estrogen and thought to both mimic
AND oppose its effects. Epidemiological
studies have shown better breast cancer survival rates of Chinese soy
eaters but no effect or mixed results on US women (Nutr Rev 568:542; JAMA 302:2437).
In cell-based studies the phytoestrogen genistein was shown to
accelerate the growth of breast cancer cells at low doses and inhibit growth at
high doses (Anticancer Res
32:1181; Nutr Rev 67:398). Such in vitro studies clearly do not translate
in vivo but these opposing actions should
give pause to those considering taking soy as a supplement. Also, the American Heart Association could
not determine any consistent findings to demonstrate a relationship between soy
consumption and menopausal symptom.
Another serious concern is allergic reaction to soy. Allergic response to soy proteins is as
common as those seen with milk, eggs, peanuts, tree nuts and shellfish but the
reaction tends to be less severe (Am Soc Nutr
Sci 134:1213S). To facilitate digestion,
soybeans, like all legumes should be thoroughly cooked. Edamame is an immature soybean which is appealing
because the young beans are easier to digest.
Tofu is a bean curd derived from soybeans, and fermented versions
include soy sauce, soybean paste, natto, and tempeh, among others. Soybeans are a common source of lecithin, a phospholipid
used as an emulsifier in many processed condiments and packaged goods. People with soy allergies should definitely read
food labels as small quantities of soy proteins have been found in some soy lecithin preparations (Int Arch Allergy Immunol 126:218).
Taken together, the observations and findings of soy-based
diet outcomes suggest that soy is a healthy phytochemical that should be consumed
in moderation. However, it should be
avoided completely if you are allergic. For
those of you concerned about genetically modified soy be sure to read the
previous blog: http://egglrock.blogspot.com/2014/09/what-you-need-to-know-about-gmo.html.
