Study finds surprising link between eating soy and dementia risk

Brittany A. Roston - Oct 22, 2020, 3:25pm CDT
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Study finds surprising link between eating soy and dementia risk

Soybeans remain a common ingredient in many foods and regional diets, serving as the basis for everything from hummus to soy sauce, soy milk, and even simple beans found in soup. However, the ingredient is controversial in certain places — in some cases with legitimate concerns and others unfounded. A new study has revealed a surprising link between eating soy and dementia risk, and it’s good news.

Many studies have been conducted on soy and compounds found in it called isoflavones. Some research has linked high consumption of these compounds with an increased breast cancer risk, at least in rodents, the reason potentially being that isoflavones are a phytoestrogen and have estrogen-like effects on the human body. Experts note that rodents and humans process soy differently, however, and that the results from rodents can’t be directly applied to humans.

That doesn’t mean one necessarily needs to avoid soy as it also provides a number of health benefits, according to Harvard. This latest study on the staple crop comes from the University of Pittsburgh, which reports that when someone eats soy, a metabolite is produced that may reduce one’s risk of developing dementia.

Certain types of gut bacteria were found to produce this metabolite when the body digests soy products; elderly Japanese individuals who produced this metabolite (equol) also had fewer brain lesions described as major dementia risk factors. The study involved blood tests on 91 elderly participants who had normal cognition at the start of the project.

The researchers split the participants up into groups based on their blood equol metabolite levels, then followed up with brain scans up to nine years later to monitor the plaque deposits and white matter lesions associated with dementia.

Pitt Public Health associate professor of epidemiology and the study’s lead author Akira Sekikawa explained:

White matter lesions are significant risk factors for cognitive decline, dementia and all-cause mortality. We found 50% more white matter lesions in people who cannot produce equol compared to people who can produce it, which is a surprisingly huge effect.

Unfortunately, the plaque buildup didn’t appear to be reduced by this metabolite, but the study found a link between equol and reduced brain lesion volumes. As well, the researchers established that the isoflavones alone weren’t enough to get this potential benefit; the reduced risk factor was only present in cases where the participants had the right gut bacteria to produce the metabolite.

As many as 70-percent of Japanese adults have the right gut bacteria to produce this metabolite when eating soy, which is also linked with a reduced risk of heart disease. In comparison, it is estimated that only up to 30-percent of Americans have the right bacteria to produce equol. However, future research may pave the way for an equol supplement intended to reduce dementia risk.


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