Soy: Good? or Bad?

Soy:
Good For Asians, like me, Chinese, in the normally consumed amount! That is for sure. For the westerners, not so sure yet! It might take another 2 - 3 years before data analysis can give us a more firm answer. Hang in there!

Is Soy Safe?
By Allan R. Handysides and Peter N. Landless

From time to time, we hear that soy foods are unsafe. What is your take on this? 
Soy foods are varied and range from the whole, cooked bean to highly processed and refined products. Soy has been popularized, especially by Adventists, who find it a suitable source of protein. Amino acids, the building blocks of protein, occur in most of our foods, and the only problem a vegetarian is likely to experience with protein is if one’s diet is not varied and balanced.

Vegetable sources of protein often lack an essential amino acid or two, and soy beans are one product that provides a more rounded amino acid profile. The use of animal products provides a good range of amino acids within the single food, but such an advantage does not hold when compared to a mixture of foods. For the vegetarian, mixing grains with legumes and nuts provides a full spectrum of amino acids that is totally satisfying to all kinds of people—athlete, growing adolescent, or even the pregnant mother-to-be. This means that soy products, as good as they are, do not have to be a part of the vegetarian diet for it to be satisfactory.

In all probability, however, there is an advantage to soy that transcends amino acid content. While there is evidence for several advantages to soy, this evidence is not of the most compelling order, because studies on food effects are very difficult to perform. Nevertheless, it’s probable that soy offers protective isoflavones and other such phytochemicals to decrease one’s risk of cancer. For men, this appears to be the case for prostate cancer, with a glass of soy milk a day providing a modicum of protection.

The anti-soy lobby brings all kinds of arguments to support their condemnation of soy. Some cite situations in which birds fed an essentially total soy diet developed crooked beaks. Others quote studies that suggest an increase in dementia for those consuming large quantities of soy. The important thing is to recognize that these are inconclusive studies and are being given disproportionate weight by those quoting them.

A few months ago there was a very well-conducted study of sufficient numbers and controls reported in The Journal of the American Medical Association (JAMA, December 9, 2009, vol. 302, no. 22) on soy food intake and breast cancer survival. This study, conducted on women in China, was able to separate soy intake into four quartiles and correlate it with survival from breast cancer. There were more than 5,000 female breast cancer survivors, followed for some five years. Those in the highest quartile of soy intake had some 30 to 40 percent less cancer recurrence. This advantage was experienced regardless of tumor estrogen receptor status, but did not increase where the intake exceeded 11 grams per day of soy protein.

This suggests a benefit to soy up to a limit. One of the difficulties in transferring this advantage to the United States might be that the Chinese tend to consume “whole” soy, not the texturized protein many in the U.S. utilize. Certainly, whole soy products such as soy milk, tofu, the whole bean, or miso (a traditional Japanese seasoning) appear to confer an advantage to female breast cancer survivors. Because this study is of high quality, it has significant meaning for breast cancer survivors and is encouraging to those who utilize soy—particularly whole soy—as part of their diet.

While benefit in this one situation does not necessarily apply across the whole spectrum of potential advantages or disadvantages, it is supportive of our recommendations that moderate amounts of soy be utilized in a balanced vegetarian diet. 

Allan R. Handysides, M.B., Ch.B., FRCPC, FRCSC, FACOG, 
is director of the General Conference Health Ministries Department. 

Peter N. Landless, M.B., B.Ch., M.Med., F.C.P.(SA), F.A.C.C., 
is ICPA executive director and associate director of the Health Ministries Department. 

Source: Adventist World

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J Nutr. 2002 Mar;132(3):566S-569S.
Soy, soy phytoestrogens and cardiovascular disease.

Clarkson TB.
Comparative Medicine Clinical Research Center, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. tclarkso@wfubmc.edu

Dietary soy protein has been shown to have several beneficial effects on cardiovascular health. The best-documented effect is on plasma lipid and lipoprotein concentrations, with reductions of approximately 10% in LDL cholesterol concentrations (somewhat greater for individuals with high pretreatment LDL cholesterol concentrations) and small increases in HDL cholesterol concentrations. Dietary soy protein improves flow-mediated arterial dilation of postmenopausal women but worsens that of men. Soy isoflavone extracts improve systemic arterial compliance, an indicator of atherosclerosis extent. Complete soy protein but not alcohol-washed soy protein reduces atherosclerosis of postmenopausal monkeys. No definite experimental evidence exists currently to establish that the cardiovascular benefits of soy protein are accounted for by its isoflavones.

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Br J Cancer. 2008 Jul 8;99(1):196-200.
Soy intake and breast cancer risk in Singapore Chinese Health Study.

Wu AH, Koh WP, Wang R, Lee HP, Yu MC.
Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA. annawu@usc.edu

We investigated the effects of soy isoflavone intake on breast cancer in a prospective study of 35,303 Singapore Chinese women enrolled during April 1993 to December 1998 in the Singapore Chinese Health Study. At recruitment, each subject was personally administered a validated semiquantitative food frequency questionnaire covering 165 food and beverage items. As of December 31,2005, 629 had developed breast cancer following an accumulation of 338,242 person-years. Duration of follow-up modified the soy-breast cancer association, the effect being twice as large among women with 10+ vs fewer years of follow-up. Neither oestrogen nor progesterone receptor status of the tumours materially influenced the association. These prospective findings suggest that approximately 10 mg of isoflavones per day, obtained in a standard serving of tofu, may have lasting beneficial effects against breast cancer development.

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Am J Clin Nutr. 2009 Apr;89(4):1155-63. Epub 2009 Feb 11.
Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis.

Yan L, Spitznagel EL.
Grand Forks Human Nutrition Research Center, ARS, USDA, Grand Forks, ND 58202-9034, USA. lin.yan@ars.usda.gov

BACKGROUND: Epidemiologic studies have shown that the consumption of soy foods may be associated with a reduction in cancer risk in humans. OBJECTIVE: The purpose of this study was to conduct a meta-analysis on the association between soy consumption and prostate cancer risk in men. DESIGN: We systematically reviewed studies obtained through a thorough Medline literature search and identified 15 epidemiologic publications on soy consumption and 9 on isoflavones in association with prostate cancer risk. We extracted the most adjusted relative risks (RRs) and odds ratios (ORs) of the highest and the lowest reported categories of intake from each study and conducted this analysis using a random-effects model in which studies with smaller SEEs are given greater weight in the summary measure. CONCLUSIONS: The results of this analysis suggest that consumption of soy foods is associated with a reduction in prostate cancer risk in men. This protection may be associated with the type and quantity of soy foods consumed.