Randomized controlled trial of the effects of soy protein containing isoflavones on vascular function in postmenopausal women

• Published in: The American journal of clinical nutrition Vol. 81; no. 1; pp. 189 - 195
• Main Authors: Kreijkamp-Kaspers, S, Kok, L, Bots, M.L, Grobbee, D.E, Lampe, J.W, Schouw, Y.T. van der
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Clinical Nutrition 2005; American Society for Clinical Nutrition, Inc
• Subjects: Aged; Biological and medical sciences; Blood Pressure - drug effects; cardioprotective effect; Circulatory system; Clinical trials; diastolic blood pressure; Diet; dietary protein; Double-Blind Method; endothelial function; endothelium; Endothelium, Vascular - drug effects; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; health promotion; Humans; isoflavones; Isoflavones - pharmacology; Menopause; Middle Aged; Milk Proteins - pharmacology; plant estrogens; Postmenopause; Proteins; soy protein; Soybean Proteins - pharmacology; Soybeans; systolic blood pressure; vasodilation; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Women; Human; Hypertension; Isoflavone; endothelial function; postmenopausal women; Cardiovascular disease; Soybean; Soy protein; Postmenopause; Female; Blood pressure; Hemodynamics; soy; Isoflavones
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/81.1.189

Background: The incidence of cardiovascular disease increases after menopause, possibly because of the decline in estrogen. Soy protein, a rich source of estrogen-like isoflavones, is hypothesized to improve vascular function. Objective: The objective of this study was to investigate whether supplementation with soy protein, a rich source of estrogen-like isoflavones, improves vascular function. Design: We performed a 12-mo double-blind randomized trial to compare the effects of soy protein containing 99 mg isoflavones/d (aglycone weights) with those of milk protein (placebo) on blood pressure and endothelial function in 202 postmenopausal women aged 60-75 y. Results: Changes in endothelial function during the intervention were not significantly different between the soy and the placebo groups. After the intervention, systolic blood pressure increased in the soy group significantly more than it did in the placebo group; the difference in change was 4.3 mm Hg (95% CI: 0.3, 8.4 mm Hg; P = 0.04) for systolic blood pressure, but only 2.0 mm Hg (95% CI: -0.74, 4.71 mm Hg; P = 0.15) for diastolic blood pressure. In the soy group only, systolic and diastolic blood pressure decreased and endothelial function improved in the equol producers, whereas systolic and diastolic blood pressure increased and endothelial function deteriorated in the equol nonproducers. Conclusions: The results of this trial do not support the hypothesis that soy protein containing isoflavones have beneficial effects on vascular function in older postmenopausal women. Whether certain subgroups of women (eg, equol producers) do benefit from the intervention remains to be elucidated.