Summary: New research suggests a metabolite produced after eating dietary soy may reduce a key risk factor for dementia.
Source: University of Pittsburgh
A metabolite generated from soy in the gut—when the right bacteria are present—may be linked to lower levels of brain white matter damage, a new study led by the University of Pittsburgh Graduate School of Public Health reports.
Published in Alzheimer’s & Dementia: Translational Research & Clinical Interventions, the study focuses on equol, a compound formed when certain gut bacteria metabolize soy isoflavones. The researchers report that older Japanese adults who produce equol had smaller volumes of white matter lesions in the brain compared with those who do not produce equol.
Lead author Akira Sekikawa, M.D., Ph.D., associate professor of epidemiology at Pitt Public Health, explained the importance of the finding: “White matter lesions are significant risk factors for cognitive decline, dementia and all-cause mortality. We found about 50% more white matter lesions in people who cannot produce equol compared to those who can produce it, which is a surprisingly large difference.”
The team measured equol levels in the blood of 91 cognitively normal elderly Japanese participants to classify them as equol producers or non-producers. Six to nine years later, participants underwent brain imaging to assess two specific markers commonly associated with dementia risk: white matter lesion volume and deposition of amyloid-beta protein, which is implicated in Alzheimer’s disease.
Their analysis showed that equol production was associated with reduced white matter lesion volumes, while it did not appear to influence amyloid-beta levels in the brain. The researchers also observed that high intake of isoflavones—the soy nutrients that can be converted into equol—did not reduce white matter lesions or amyloid-beta unless equol was actually produced by the gut microbiome.
Sekikawa and colleagues propose that the health benefits attributed to soy in some populations may depend on whether a person’s gut bacteria can convert isoflavones into equol. Previous work by the same team has linked equol production with lower heart disease risk, and because cardiovascular health is closely tied to brain health, equol production could potentially help protect both heart and brain as people age.
Epidemiological studies from Japan—where soy is a common dietary staple—have suggested lower risks of heart disease and dementia associated with soy isoflavone intake. By contrast, many clinical trials conducted in the United States have not consistently shown these benefits. The authors suggest that differences in the gut microbiome may help explain this discrepancy: an estimated 40–70% of Japanese people harbor gut bacteria capable of producing equol, while only about 20–30% of Americans do.
Looking ahead, Sekikawa said equol supplements might eventually be evaluated as part of broader, diet-based prevention strategies that have been associated with lower dementia risk—such as the DASH and Mediterranean-style dietary patterns. However, he emphasized caution.
“This type of study generates interest, but we cannot conclude that equol prevents dementia until randomized clinical trials provide sufficient evidence,” Sekikawa said. He and his team hope to test the neuroprotective effects of equol supplements in a future randomized clinical trial before recommending them for dementia prevention.
The study team includes collaborators from the National Cerebral and Cardiovascular Center in Japan—Aya Higashiyama, M.D., Ph.D.; Masafumi Ihara, M.D., Ph.D.; Makoto Watanabe, M.D., Ph.D.; Chikage Kakuta, M.A.; Yoshihiro Kokubo, M.D., Ph.D.; and Yoshihiro Miyamoto, M.D., Ph.D.—and researchers from the University of Pittsburgh, including Brian J. Lopresti, M.S.; Howard Aizenstein, M.D., Ph.D.; Yuefang Chang, Ph.D.; Zheming Yu, M.D., M.P.H.; Chester Mathis, Ph.D.; William Klunk, M.D., Ph.D.; Oscar L. Lopez, M.D.; Lewis H. Kuller, M.D., Dr.P.H.; and Chendi Cui, Ph.D.
Funding: This research was supported by the National Institutes of Health/National Institute on Aging grant RF1 AG051615.
About this dementia research news
Source: University of Pittsburgh
Contact: Allison Hydzik – University of Pittsburgh
Image: The image is in the public domain
Original Research: The full study appears in Alzheimer’s & Dementia: TRCI.