Soy foods linked to lower dementia risk, better memory, studies suggest

Soy is one of the foods researchers have consistently studied in connection with dementia. It is rich in high-quality protein and isoflavones, bioactive compounds considered among its most significant components. Isoflavones in particular have shown potential to influence multiple pathways linked to Alzheimer's disease, including intracellular signaling.

A neurology research team at Nanchang University in China found that people who consumed more soy foods had a lower risk of developing dementia, according to a meta-analysis published in August 2025 in the international journal Frontiers in Nutrition.

The team pooled data from six studies covering 68,691 participants and found an association between higher soy food consumption and a reduced likelihood of developing major neurocognitive disorders. In dose-response analyses, each additional gram of daily soy or natto intake was associated with an 8 percent and 14 percent lower risk of major neurocognitive disorders, respectively. The risk-reduction trend was more pronounced among people who had not experienced a stroke.

"Dietary modification incorporating soy foods may have a meaningful effect on reducing the risk of major neurocognitive disorders, with fermented products such as natto potentially offering an even greater risk-reduction benefit," the team said.

A literature review published in December 2025 in the international journal Alzheimer's & Dementia by a research team at Anhembi Morumbi University in Brazil also found that soy isoflavones may help prevent Alzheimer's disease.

"Genistein improved cognitive function in patients with prodromal Alzheimer's disease and showed a positive effect in inhibiting beta-amyloid accumulation," the team said, adding that further research is needed to evaluate its potential as an intervention to slow the progression of Alzheimer's disease.

A study published in June 2025 in the international journal Nutrients by a research team at Loma Linda University School of Public Health in the United States found that consuming fermented soy may help improve memory in older adults. The findings suggest that various bioactive compounds in fermented soy — including peptides and aglycone-form isoflavones — may help regulate oxidative stress and neuroinflammation.

"Consuming fermented soy may help slow age-related cognitive decline," the team said.