Wednesday Bubble: This is your brain. This is your brain on phytoestrogens.

Posted by Liz on Apr 11, 2012 in memory/learning | 1 comment

Do phytoestrogens improve cognitive performance?

This is the first I’ve heard that phytoestrogens, i.e. isoflavones, lignans (a major form of phytoestrogens found in flaxseed and sesame seeds) and coumestans (a type of phytoestrogen found in split peas, pinto beans and lima beans) may help boost attention, executive function and memory. Yet, similar to other alternative strategies, the studies examining these benefits have yielded mixed results. Moreover, a lot of these studies have been based on short-term and not long-term use of phytoestrogens, have failed to determine how these compounds may influence brain function, and have not looked specifically at women undergoing the menopausal transition, at least until now.

This time, researchers took a cohort of women actively involved in the Study of Women’s Health Across the Nation. All 1,677 women who saw the study through to its end were between the ages of 42 and 52, premenopausal, early or late perimenopausal, and naturally or surgically postmenopausal, and were not using hormones. Importantly, this group of women included several ethnic groups, which allowed the researchers to see if phytoestrogens behaved differently depending on ethnicity; they included white, African American, Hispanic, Chinese and Japanese.

• Diet was regularly evaluated and included interviews, open ended questions and specifically, daily intake of four types of isoflavones, four types of lignans and coumesterol, which is the main phytoestrogen in coumestans. In Asian women, soybeans, tofus and soy milk were the main sources of isoflavones while in non-Asian women, soy mik, tofu and meat substitutes (e.g. seitan) were the main sources. Regardless of ethnic group, coffee and tea were the primary sources of lignans, and bean sprouts, the main source of coumestans.
• Cognitive testing was done in the morning and always in the same language for bilingual women. These tests included processing speed, immediate and delayed recall and working memory.
• The study took place over 6 years and women were visited 10 times.

So, what did they learn?

First, phytoestrogens appear to affect cognitive function differently, depending on the type and stage of menopause. For example, Asian women whose diets had high levels of isoflavones tended to process information quicker but only during early perimenopause and postmenopause. Conversely, during the same time, these women had poor recall. Non-Asian women who ate a lot of isoflavones also had poor recall during perimenopause. Moreover, women who ate the most lignans, regardless of ethic group, appeared to have better memories but only during late perimenopause. Overall, coumestans did not appear to influence brain function whatsoever.

It’s all sort of confusing, isn’t it? What’s more, even the researchers admit that the effects, when seen, were quite small. And the distinctions between Asian and non-Asian women? It’s the chicken/egg paradigm: is it dose or DNA? At the end of the day, it’s all bubble burstable because scientists remain unclear as to how phytoestrogens affect the way we process information. It is possible that its due to their antioxidant characteristics, but who knows?

Meanwhile? Despite potential GI tract issues (e.g. gas, bloating, constipation), incorporating higher levels of phytoestrogens into your diet may be a good thing. Your brain on phytoestrogens? Who doesn’t need a little boost?