Adhering to what’s known as a green-Mediterranean diet – which includes green tea and the “supergreen” Mankai – is tied to slower brain aging, according to a Harvard-led study published in the October 2025 issue of Clinical Nutrition.
Researchers evaluated data over 18 months from nearly 300 people (90% male) ages 30 and older with obesity or abnormal blood lipids. Each participant was taking part in the DIRECT PLUS trial, one of the longest-running studies on the link between brain health and diet. All participants received nutritional guidance, instructions regarding physical activity, free gym membership, and nutritional and physical activity sessions at their workplaces.
Participants’ diets varied by assignment to one of three groups. One group ate a standard, healthy diet. The second consumed a traditional, calorie-restricted Mediterranean diet that was low in processed foods and rich in vegetables and replaced red meat with poultry and fish. The last followed a calorie-restricted green-Mediterranean diet, which added green tea and Mankai, a trademarked strain of duckweed that’s available as a powder or frozen cubes. The two Mediterranean diets also included 28 grams (1/4 cup) of walnuts per day.
Researchers measured 87 proteins in the participants’ blood samples. They found that higher levels of certain proteins were associated with accelerated brain aging (as determined by brain scans). But these protein levels were lower over the course of the study in participants who followed the green-Mediterranean diet. The researchers hope to use the findings to map protein “signatures” in the brain that can offer insight into how diet and other measures may help preserve brain health as people age.
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