Almost everyday I come across someone who avoids soy because they think eating soy products will do one of the following: a) increase their risk of cancer; b) if they had breast cancer, will make it worse or come back; or c) will mess up their hormones (and, therefore, turn men into women). If you are concerned about choice c, please refer to my blog from January 13, 2011 entitled: “PhytoeSTROGEN's: A little hormonal, yes. But immasculating? No!” I ask these people why they think these things about soy, and usually they say they heard it from a friend, saw it on some daytime talk show, or read an article once. If you are going to cut something out of your diet that has as many benefits as soy, I urge you to look to first look to reputable health sources, or review the meta-analysis studies on your own. So, this goes not just for soy, but if you hear in the future that dairy is bad- don't cut it out immediately, first do your research! (FYI: I would not advise cutting dairy out of your diet, only high-fat dairy).
Anyway, I am always thoroughly confused why there is so much negative thinking about soy, when in fact, the majority of the nutrition research shows soy being nothing but beneficial for a whole slew of health issues. The nutritional benefits of soy include that it is:
1. An excellent source of complete protein (containing all the essential amino acids)
2. Low in saturated fat
3. Cholesterol Free
4. High in mono- and poly- unsaturated fats
5. Usually fortified with calcium, vitamin D, vitamin B12
6. A good source of fiber
The health benefits of consuming soy include, but are not limited to:
1. When substituting soy protein for traditional protein sources (meat, dairy), total cholesterol, LDL’s, and VLDLs and triglycerides are lowered while HDL’s (the good cholesterol) are increased in adults and children
2. Soy intake during childhood and adolescence is associated with up to a 60% reduction of breast cancer risk later in life.
3. Soy protein has also shown to decrease blood pressure when compared to milk protein.
4. Soy contains high levels of antioxidants, which help to combat free radicals in the body which can speed up the aging process and increase disease risk.
Even though I wrote about phytoestrogens in a previous blog post, I will refresh your memory on this debate. “In adult men, clinical studies show that neither isoflavone supplements nor soyfoods affect circulating testosterone or estrogen levels or sperm or semen parameters. Although soy may have minor effects on hormone levels in adult women, it is likely these effects are clinically irrelevant”(1). One study published by the American Society for Clinical Nutrition came to the conclusion that: “[. . .] soy isoflavones have little biologically relevant estrogenic effect in vivo in postmenopausal women (4).” This means that from their study, soy does appear to change the estrogen levels in women.
Twenty-four trials evaluated subjects without a history of cancer for effects of soy on tumor-related biomarkers. No study reported the development of cancer as an outcome. Most studies measured the effect of soy on estrogens and estrogen metabolites as well as on estrogenicity indicators. There were also trials that evaluated correlations between soy and possible cellular pathways of cancer prevention. No causal relationship could be established between these markers and cancer because they do not represent known risk factors for cancer disease. Only 4 studies reported on testosterone levels, which is a risk factor for prostate cancer, and are discussed under Endocrine Function (5).
MY RECOMMENDATIONS:
Overall, I believe soy foods are incredibly good for your health. Asian populations have been eating the isoflavones from soyfoods for centuries with no adverse effects, and actually, these populations tend to be much healthier than Americans. Soy is a great way to get in vitamins, minerals, fiber, and complete protein into the diet. I recommend trying to stick to organic soy products (tofu, soymilk, edamame, etc.) and avoiding isoflavone supplements (I’m not a believer in most isolated supplements anyway….). Don’t be paranoid about soy, there are probably a lot of things in your diet that are doing much more harm that you haven’t cut out (alcohol, candy, soda, etc………).
References:
1. Diggers, J. “Soy Can Supply Key Nutrients to Children and Adolescents.” The Soy Connection. Journal of the American Dietetic Association. Fall 2011.
2. Hamilton-Reeves JM, Vazquez G, Duval SJ, Phipps WR, Kurzer MS, Messina
3. Messina M. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertil. Steril. 2010, 93, 2095-104.
4. Teede HJ, Dalais FS, McGrath BP. Dietary soy containing phytoestrogens does not have detectable estrogenic effects on hepatic protein synthesis in postmenopausal women. American Journal of Clinical Nutrition. 2004 Mar;79(3):396-401
5. Balk E, Chung M, Chew P, et al. Effects of Soy on Health Outcomes. Summary, Evidence Report/Technology Assessment: Number 126. AHRQ Publication Number 05-E024-1, August 2005. Agency for Healthcare Research and Quality, Rockville , MD.
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