by Dr. Leo Galland
Soy contains unique bioflavonoids with an isoflavone structure, like genistein and daidzen, which have estrogen-like effects in the human body.
Research done in the United States and Australia suggests potential benefits of soy isoflavones on healthy post-menopausal women. However, the benefits of soy on cognition have not materialized in some studies, with some research finding no benefit for cognitive function when soy isoflavones were given to women.
One study on soy and post-menopausal women done at Washington State University found that soy wasn’t helpful for improving cognitive function. The study, published in the Journal of Nutrition, Health and Aging concluded: “Soy isoflavones consumed as a food or supplement over a 16-week period did not improve or appreciably affect cognitive functioning in healthy, postmenopausal women.” (Fournier et al.)
Research on soy at Johns Hopkins University found no effects on cognition, although the study, using relatively high doses (160 milligrams per day), demonstrated improvement in well-being and quality of life among women who had just entered menopause. The team at Johns Hopkins noted “The use of isoflavones, as an alternative to estrogen therapy, may be potentially useful and seemingly safe in this group of women who are looking for relief from menopausal symptoms” (Basaria et al.)
References and Abstracts:
J Nutr Health Aging. 2007 Mar-Apr;11(2):155-64. The effects of soy milk and isoflavone supplements on cognitive performance in healthy, postmenopausal women.
Fournier LR, Ryan Borchers TA, Robison LM, Wiediger M, Park JS, Chew BP, McGuire MK, Sclar DA, Skaer TL, Beerman KA. Department of Psychology, Washington State University, Pullman, WA 99164-4820, USA. Fournier@wsunix.wsu.edu
RATIONALE: The decline in estrogen concentrations in women after menopause can contribute to health related changes including impairments in cognition, especially memory. Because of the health concerns related to hormone replacement therapy (HRT), alternative approaches to treat menopausal symptoms, such as nutritional supplements and/or diet containing isoflavones, are of interest.
OBJECTIVES: This study investigated whether soy isoflavones (soy milk and supplement) could improve cognitive functioning in healthy, postmenopausal women.
PARTICIPANTS, INTERVENTION AND DESIGN: A total of 79 postmenopausal women, 48-65 years of age, completed a double-blind, placebo-controlled trial in which they were randomly assigned to one of three experimental groups: cow’s milk and a placebo supplement (control); soy milk and placebo supplement (soy milk, 72 mg isoflavones/day); or cow’s milk and isoflavone supplement (isoflavone supplement, 70 mg isoflavones/day).
MEASUREMENTS: Cognitive functioning was assessed using various cognitive tasks before the intervention (baseline) and after the intervention (test).
RESULTS: In contrast to predictions, soy isoflavones did not improve selective attention (Stroop task), visual long-term memory (pattern recognition), short-term visuospatial memory (Benton Visual Retention Test), or visuo-spatial working memory (color match task). Also, the soy milk group showed a decline in verbal working memory (Digit Ordering Task) compared to the soy supplement and control groups.
CONCLUSION: Soy isoflavones consumed as a food or supplement over a 16-week period did not improve or appreciably affect cognitive functioning in healthy, postmenopausal women.
J Endocrinol Invest. 2009 Feb;32(2):150-5.Effect of high-dose isoflavones on cognition, quality of life, androgens, and lipoprotein in post-menopausal women.
Basaria S, Wisniewski A, Dupree K, Bruno T, Song MY, Yao F, Ojumu A, John M, Dobs AS.Department of Internal Medicine, Division of Endocrinology and Metabolism, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. shehzad.basaria@bmc.org
CONTEXT: Recent interventional studies indicate that post-menopausal hormone replacement therapy is associated with an increased risk of cardiovascular mortality and breast cancer. Isoflavones, a class of plant estrogens, have structural similarities to estradiol. Hence, isoflavones may exert beneficial estrogenic health effects in postmenopausal women with fewer adverse effects.
OBJECTIVE: To evaluate the effect of high-dose isoflavones on self-reported quality of life (QOL), cognition, lipoproteins and androgen status in post-menopausal women.
DESIGN AND SUBJECTS: Double-blind, randomized, placebo-controlled, 12-week trial of 93 healthy, ambulatory, post-menopausal women (mean age 56 yr). The study was conducted at a tertiary care center in the United States.
INTERVENTION: Participants were randomly assigned to receive 20 g of soy protein containing 160 mg of total isoflavones vs taste-matched placebo (20 g whole milk protein). Both soy and the placebo were provided in the form of a powder to be mixed with beverages.
MAIN OUTCOME MEASURES: QOL was judged by the Menopause-specific Quality of Life (MENQOL) questionnaire while cognitive function was assessed with standard instruments. Total, free, and bioavailable testosterone, gonadotropins, SHBG, and fasting lipids were measured.
RESULTS: Eighty-four women (90%) completed the study (active=38, placebo=46). There was a significant improvement in all 4 QOL subscales (vasomotor, psychosexual, physical, and sexual) among the women taking isoflavones, while no changes were seen in the placebo group. No significant changes in cognition, serum androgens or plasma lipids were seen within any of the groups. However, at the end of the study, a group-by-time interaction was observed such that total testosterone and HDL levels were significantly lower in the isoflavones compared to placebo groups.
CONCLUSION: High-dose isoflavones is associated with improved QOL among women who have become menopausal recently. Hence, the timing of isoflavone supplementation with regards to the onset of menopause appears to be important. The use of isoflavones, as an alternative to estrogen therapy, may be potentially useful and seemingly safe in this group of women who are looking for relief from menopausal symptoms.
