DOI: 10.1097/gme.0b013e3181f56268
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Issn Print: 1072-3714
Publication Date: 2010/11/01
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Excerpt
We thank you for the opportunity to respond to this "Letter to the Editor" and for the comments on our recent publication regarding 1-year soy supplementation not improving the lipid profile in postmenopausal women. As mentioned in the letter, the cholesterol-lowering effects of soy are, at best, very modest, including what is reported by the latest meta-analysis (decrease in total cholesterol level of 3.9 mg/dL, or 1.77%, and in low-density lipoprotein cholesterol level of 5.0 mg/dL, or 3.58%).1 Collectively, most original research and meta-analyses support our conclusions that soy has very little lipid-lowering properties and do not support a health claim for soy and cholesterol.2-6 However, we would like to point out that the cardioprotective effects of soy isoflavones may be unrelated to their cholesterol-lowering properties. For instance, our previous work in the Golden Syrian hamster model of ovarian hormone deficiency-induced postmenopausal hypercholesterolemia has supported a role for soy isoflavones, independent of the protein source.7 Results of that study showed that at all doses of isoflavone (9.5 mg/kg diet, low dose; 19 mg/kg diet, medium dose; or 38 mg/kg diet, high dose), there was a significant reduction in fatty streak area compared with that in the ovariectomized control group.7
With regard to the health claim for oat bran, an update was issued in 2002 to reflect the "significant scientific agreement that a relationship exists between the β-glucan soluble fiber of certain whole oat sources and the reduction of risk of CHD by lowering blood cholesterol levels."8 This update from the Food and Drug Administration stated that they amend "the regulation that authorizes a health claim on the relationship between soluble fiber from whole oats and reduced risk of CHD to include this additional source of β-glucan soluble fiber."8 A similar situation may exist for soy in that the optimal doses for the active compounds, for example, isoflavones and saponins, have yet to be determined. Hence, the debate on the cholesterol-lowering properties of soy most probably will continue until standard levels of active compounds are reached.
In conclusion, we agree that soy protein has garnered a lot of attention because it is among the richest edible sources of isoflavones that has been linked to numerous health benefits. Furthermore, studies are necessary to examine the extent to which soy or its components affect certain diseases. Meanwhile, for healthy individuals, eating soy foods is advisable because these are rich in quality protein, polyunsaturated fat, fiber, vitamins, and minerals and are low in saturated fat.
