Green tea, walnuts and aquatic plant Mankai linked to slower brain aging, study finds

RIYADH, November 13, 2025 (Saudi Arabia Breaking News) – A combination of green tea, walnuts and the aquatic plant Mankai may help slow biological markers of brain aging, according to an international research team studying dietary impact on neurodegeneration.

The findings come from an 18-month randomized trial involving nearly 300 adults, published in Clinical Nutrition. The study compared three diets and found that participants who followed a plant-forward “green Mediterranean” diet recorded the largest decrease in Galectin-9, a blood protein associated with faster brain aging on MRI scans.

Researchers from Harvard University, Ben-Gurion University in Israel and the University of Leipzig in Germany analysed blood biomarkers and compared them with MRI-estimated brain age. Participants on the enhanced Mediterranean diet — richer in plant-based foods and lower in red and processed meat — showed MRI patterns consistent with a “younger” biological brain age.

Senior study author Iris Shai, adjunct professor of nutrition at Harvard’s T.H. Chan School of Public Health, said lowering Galectin-9 may indicate reduced inflammatory activity linked to cognitive decline and neurodegenerative disease. She said the aim was to examine whether a diet rich in natural polyphenols “could actually slow the biological aging of the brain.”

The green Mediterranean diet featured higher levels of polyphenols from sources such as green tea, walnuts, olive oil, fruits and vegetables, with Mankai — an aquatic plant high in protein, iron and vitamin B12 — added as a novel component. According to the study, green tea’s EGCG antioxidants and the healthy fats and polyphenols in walnuts appeared to play a significant role in the observed changes.

Participants following a standard Mediterranean diet or general healthy eating guidelines showed some improvement, but the greatest reductions in Galectin-9 occurred among those in the green Mediterranean group.

Earlier studies by the same research group have linked Mankai to improvements in blood sugar regulation, metabolism, gut health and inflammatory markers, all of which may influence cognitive aging.

Researchers noted that most trial participants were men with obesity or cholesterol issues, and said additional investigations are needed to determine whether the findings apply to other populations. They also cautioned that while the results point to biological markers associated with brain aging, they do not prove prevention of Alzheimer’s disease or cognitive decline.

Experts said the findings add to growing evidence that higher plant intake and reduced red and processed meat consumption may support long-term brain health.