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Ames, IA, United States

Zhou Y.,Nutrition and Wellness Research Center | Alekel D.L.,Nutrition and Wellness Research Center | Dixon P.M.,Iowa State University | Messina M.,Loma Linda University | Reddy M.B.,Nutrition and Wellness Research Center
Journal of Women's Health | Year: 2011

Background: Soy foods have been substituted for meat in recent years because of proposed health benefits. Research indicates, however, that soy protein and phytate in soy products inhibit the absorption of divalent cations. Methods: Our study was primarily designed to determine the effect of consuming two to three servings per day of soy foods, providing ∼19g protein and ∼36mg isoflavones, on iron and zinc status in premenopausal women during a 10-weeks period. As secondary outcomes, we also tested the effect of soy foods on biochemical markers of bone and thyroid hormones. Nonsmoking women (18-28 years) without chronic disease, anemia, pregnancy, or irregular menstrual cycles were randomly assigned to either the soy food (SF, n=31) or animal food (AF, n=32) group. Blood and urine samples and 3-day dietary records were collected at baseline and postintervention. Results: At baseline, iron and zinc status, bone markers, and thyroid hormones were not different between groups. After intervention, no significant changes were observed in hemoglobin, transferrin saturation, serum iron, ferritin, or transferrin receptor (TFR) concentrations. Plasma zinc, but not serum alkaline phosphatase, significantly decreased in both groups (-0.8μmol/L). The change in bone-specific alkaline phosphatase was significant between SF (1.5U/L) and AF (-0.7U/L) groups. No significant changes were observed in bone resorption, thyroid-stimulating hormone (TSH), or free thyroxine after soy food intake. Conclusions: Incorporating ∼19g soy protein from soy foods for 10 weeks had no significant effect on iron or zinc status, bone resorption or formation, or thyroid hormone status in premenopausal women. © 2011, Mary Ann Liebert, Inc.

Matvienko O.A.,University of Northern Iowa | Alekel D.L.,Nutrition and Wellness Research Center | Genschel U.,Iowa State University | Ritland L.,Nutrition and Wellness Research Center | And 2 more authors.
Menopause | Year: 2010

OBJECTIVE: One of the multiple health benefits of soy protein or its isoflavones may be their purported favorable effect on body composition. We examined the effect of isoflavones extracted from soy protein on overall and regional body composition, taking into account appetitive hormones as potential mediators, as well as the direct effect on appetitive hormones. METHODS: This randomized, double-blind, placebo-controlled multicenter trial included 229 healthy postmenopausal women (age, 45.8-65 y; body mass index, 24.9 ± 3.0 kg/m) who consumed placebo or soy isoflavone (80 or 120 mg/d) tablets for 12 months. We used intent-to-treat analysis to examine changes in body composition (whole-body lean mass, whole-body fat mass, androidal fat mass, and androidal-to-gynoidal fat mass ratio) and appetitive hormones (insulin, leptin, ghrelin, and adiponectin) in response to treatment. RESULTS: Repeated-measures analysis of variance indicated that soy isoflavone treatment did not exert a significant effect on body composition measures (P value from 0.36 to 0.79) or appetitive hormone concentrations; the inclusion of covariates in statistical models did not alter these results. Independently of treatment, leptin and ghrelin related inversely to each body composition measure (P values from 0.044 to ≤0.0001). Adiponectin related inversely to all fat measures (P values from 0.0004 to <0.0001). Time since last menstrual period related directly to all fat measures (P values from 0.06 to 0.0055). Dietary fat contributed to whole-body (P = 0.028) and androidal (P = 0.017) fat mass. CONCLUSIONS: Our findings do not support a favorable effect of soy isoflavone tablets on body composition in healthy postmenopausal women. © 2010 by The North American Menopause Society.

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