A Japanese study looking at 128 patients' fecal samples, found that fecal concentrations of ammonia, indole, skatole and phenol were higher in dementia patients compared to those without dementia, while levels of beneficial Bacteroides were lower in dementia patients.
https://www.eurekalert.org/pub_releases/2019-01/aha-it012519.php
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The findings were presented at the American Stroke Association's annual conference.