To recommend or not to recommend soy foods

Abstract

To the Editors: The article by Dwyer et al adds to the growing database on the phytoestrogen (isoflavone) content of soy foods (Dwyer JT, Goldin BR, Saul N, Gaultieri L, Barakat S, Adlercreutz H. Tofu and soy drinks contain phytoestrogens. J Am Diet Assoc. 1994;94: 739–743). These values are needed because of the probable physiologic effects of isoflavones and because soy foods are for the most part the only appreciable source of isoflavones. However, I disagree somewhat with Saul's perspective in the accompanying interview (p 741). Saul states that “there is not enough scientific evidence available for dietitians to recommend that specific amounts of soy products…be added to the diet” and that “if persons enjoy soy products, I suggest they use them as a meat substitute.” Although it may be true that there are not enough data to recommend specific amounts of soy foods, there are many reasons for dietitians to recommend that consumers use soy foods, and not just as meat substitutes. Traditional soy foods are low in saturated fat and are cholesterol free. Soy protein is of the highest quality and, as reviewed in a previous issue of the Journal, is hypocholesterolemic in subjects with elevated cholesterol levels (1.Carroll KK Review of clinical studies on cholesterol-lowering response to soy protein.J Am Diet Assoc. 1991; 91: 820-827Google Scholar). Furthermore, soy protein is of potential value in the treatment of patients with chronic renal insufficiency, favorably affects calcium metabolism (in addition, many soy foods are excellent sources of highly absorbable calcium), and preliminary data indicate that phytoestrogens in soybeans inhibit bone resorption. With respect to cancer, although there are inconsistencies, the epidemiologic data suggest that consuming as little as one serving of tofu or soy milk per day is associated with a reduced risk of several kinds of cancer (2.Messina MJ Persky V Setchell KDR Barnes S Soy intake and cancer risk: a review of the in vitro and in vivo data.Nutr Cancer. 1994; 21: 113-131Google Scholar). For these reasons, and because there is no apparent toxicity associated with consuming modest amounts of soy foods, dietitians would serve their clients well by encouraging them to incorporate soy foods into their diets. Certainly, a recommendation to consume one serving per day is reasonable, practical, and justifiable. Soy foods are not a magic bullet but they do represent an important addition to a healthful diet.