Soy contains isoflavone and several studies have reported that isoflavone supplementation can improve cognitive function. A new study evaluated whether the supplementation could improve cognitive function in postmenopausal women. The findings were published online on July 7 in the journal Menopause by researchers in China.
The study authors note that although several studies have reported a benefit on cognitive function, the findings remain controversial. Therefore, the conducted a meta-analysis to determine whether isoflavones could improve cognitive function in postmenopausal women. (A meta-analysis is a compilation of data from several studies to clarify a point.)
The investigators searched databases and Web sites for relevant studies up to March 2014. To clarify the findings, two reviewers independently verified all randomized controlled trials that appeared suitable for study inclusion. Those deemed suitable were evaluated using the Jadad scale and the Risk of Bias Tool from the Cochrane handbook for systematic reviews of interventions. Any disagreement on study quality or data mining was resolved by consensus; if needed, a third reviewer was consulted. Average differences in cognitive function test scores were calculated between soy isoflavone-treated and placebo-treated groups.
After collecting all appropriate data, the researchers conducted a meta-analysis of 10 placebo-controlled randomized, controlled trials of soy isoflavone supplementation (1,024 participants; treatment duration ranged from 6 weeks to 30 months). The overall in cognitive function test scores was statistically significant. Improvement in visual memory was also statistically significant. The data was subjected to subgroup analyses that revealed benefits for residents of non-US nations, average age younger than 60 years, and for treatment duration less than 12 months.
The authors concluded that soy isoflavone supplementation appeared to have a positive effect on improving cognitive function and visual memory in postmenopausal women. Furthermore, there may be a critical window of opportunity in initiating soy isoflavone supplementation at an earlier age in postmenopausal women. In addition, geography and treatment duration appear to be factors influencing the benefit of soy isoflavone supplementation. They recommended that all women in the included studies should be followed up to observe the incidence of Alzheimer's disease and dementia. In addition, they recommended that future studies should report any adverse effects of soy isoflavone supplementation.
Take home message:
Soy isoflavones are widely available. Edamame bean is a preparation of immature soybeans in the pod, found in the cuisine of Taiwan, China, Japan, Indonesia, and Hawaii. The pods are boiled or steamed and served with salt. Many find them tasty. Soy milk is also available.