Natural plant compounds known as polyphenols, found in berries, tea, cocoa, coffee, and extra virgin olive oil, may positively influence biological processes linked to Alzheimer’s disease and other disorders marked by the gradual loss of nerve cells, according to a review by researchers at Semmelweis University.

The researchers reviewed hundreds of previous laboratory, animal, population-based, and clinical studies, finding that polyphenols may support nerve cell function through their antioxidant and anti-inflammatory properties while helping counteract harmful processes associated with brain aging.

Particular attention has been paid to the Mediterranean diet, rich in vegetables, fruits, legumes, whole grains, fish, and olive oil, as well as the MIND diet, which was specifically developed to support brain health by emphasizing leafy green vegetables and berries while limiting red meat, butter, cheese, sweets, and fried and fast foods. Among the compounds frequently examined were EGCG, a main antioxidant in green tea; the pigments responsible for the color of berries; flavanols found in cocoa; and curcumin, the compound that gives turmeric its characteristic yellow color.

“Polyphenols are not miracle cures, but research suggests they may be promising tools for supporting healthy brain aging. The focus, however, should not be on dietary supplements but on a varied diet rich in plant-based foods,” said Dr. Mónika Fekete, Assistant Professor at the Institute of Preventive Medicine and Public Health of Semmelweis University and senior author of the study.

“This may help explain why the same diet does not affect everyone in the same way. In the future, personalized nutrition could help us better understand who is most likely to benefit from a polyphenol-rich diet,” added Dr. Noémi Mózes, Assistant Professor at the same institute and the study’s first author.

A substantial proportion of polyphenols is not absorbed directly; instead, they are transformed by gut bacteria into compounds that may influence inflammatory processes, cellular energy metabolism, and, through these mechanisms, nervous system function. Because gut microbiome composition varies considerably from person to person, the same foods may not produce identical effects in everyone.

More than 55 million people worldwide are living with dementia, according to the World Health Organization, and that number is expected to rise in the coming decades. The researchers emphasize that despite encouraging findings from human studies, there is currently insufficient evidence to recommend any single food or nutrient as a stand-alone strategy for preventing dementia — there is no miracle diet. Existing evidence, however, suggests that regularly eating more vegetables, fruits, berries, fiber-rich foods, fish, and nuts while limiting highly processed foods may help support healthy brain aging and preserve cognitive function over time.

Journal: Nutrients
DOI: 10.3390/nu18091470
Publication Date: July 14, 2026

Source: EurekAlert