A soy a day doesn't necessarily increase brain power, new research suggests. In a study published in Neurology journal, researchers say there is no evidence to support the notion that soy supplements will improve the mental abilities of older women.
Dr. Wendy Mack from the Keck School of Medicine and colleagues from the University of Southern California, Stanford University and the University of Hawaii learned of soy's cognitive benefits (or lack thereof) when they designed an experiment designed to ascertain the effects that daily doses of dietary soy isoflavones would have on cognitive abilities of older women compared to traditional Asian diets. To this end, they selected 350 postmenopausal women between the ages of 45 - 92 years to participate in the Women's Isoflavone Soy Health trial. Participants were randomly assigned a daily dose of 25 g of soy protein supplement or milk protein placebo.
At the outset and again 2.5 years later, Mack's team compared the cognitive abilities of the two groups, based on changes in neuropsychological test scores. Working from the results of the 313 women who completed the study, the researchers found that soy protein had little effect - positive or negative - on the cognitive abilities of either group. Put another way, soy supplements did not boost the brain power of postmenopausal women involved in the Women's Isoflavone Soy Health trial.
This result comes as a shock when people stop to think about it. Isoflavones are a specialized class of organic compounds with phytoestrogenic (plant estrogen) properties. This is important because estrogen is known to influence cognition, including memory improvement and protection against brain cell loss.
According to Mack's data, women who took soy isoflavone showed some improvement in visual memory. But the results of other factors and individual test scores failed to show any significant benefit among a subgroup of younger postmenopausal participants.
When the research team analyzed all of the data they concluded:"For healthy postmenopausal women, long-term dietary soy isoflavone supplementation in a dose comparable to that of traditional Asian diets has no effect on global cognition but may improve visual memory."
Interestingly, in a similar study published in a 2003 issue of Menopause journal, 56 postmenopausal women between the ages of 55 - 74 years were given isoflavones or placebo. The results of the SOy and Postmenopausal Health In Aging Study (SOPHIA) showed that women who received isoflavones showed greater verbal memory and other cognitive abilities compared to women who only received placebo.
As women become older, there is a risk of cognitive decline, Alzheimer's disease and other forms of dementia. Estrogen has been proven to increase concentrations of choline acetyltransferase, an enzyme crucial to the neurotransmitter acetylcholine.
In summary, results of the Women's Isoflavone Soy Health trial show the organic compounds had neither a beneficial nor adverse effect on the participants' health or mental skills. By contrast, the SOPHIA study provides evidence that soy isoflavones improve the cognitive abilities of postmenopausal women.
Therefore, what it boils down to is weighing the pros and cons of isoflavone supplementation on a personal level. Ultimately, the decision whether or not to take isoflavones is entirely up to you.
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Henderson, V., St. John, J., Hodis, H., Kono, N., McCleary, C., Franke, A., Mack, W., & , . (2012). Long-term soy isoflavone supplementation and cognition in women: A randomized, controlled trial Neurology, 78 (23), 1841-1848 DOI: 10.1212/WNL.0b013e318258f822
Kritz-Silverstein, D., Von M??hlen, D., Barrett-Connor, E., & Bressel, M. (2003). Isoflavones and cognitive function in older women: the SOy and Postmenopausal Health In Aging (SOPHIA) Study Menopause, 10 (3), 196-202 DOI: 10.1097/00042192-200310030-00004
Sherwin, B. (2003). Estrogen and Cognitive Functioning in Women Endocrine Reviews, 24 (2), 133-151 DOI: 10.1210/er.2001-0016
"Soy Supplements Don't Improve Women's Thinking Ability" copyright 2012 Living Fit, Healthy and Happy(SM). All Rights Reserved.