A new study has shown that an "unexpected trio" of green tea, walnuts, and a small aquatic plant called "Mankai" may help preserve brain youthfulness.
According to a report published by Fox News, the results of an 18-month randomized trial involving about 300 participants showed that following a plant-rich Mediterranean diet reduces the risk of memory loss and dementia. It is associated with lower levels of a blood protein called "galectin-9," which is linked to indicators of accelerated brain aging on MRI scans, according to a study published in the journal "Clinical Nutrition."
Researchers from Harvard University and Leipzig University in Germany compared the participants' blood proteins with MRI scans that estimated "brain age." Participants who followed the plant-rich Mediterranean diet, low in red and processed meats, showed the greatest decrease in levels of the "galectin-9" protein linked to accelerated brain aging, while MRI scans suggested their brains were "younger" than their actual chronological age.
"Nutrition affects brain biology," said the study's lead author, Dr. Iris Shai, a visiting professor at Harvard's T.H. Chan School of Public Health, in an interview with Fox News. She added that reducing "galectin-9" levels could mean limiting the inflammatory processes that contribute to cognitive decline, memory loss, and neurodegenerative diseases like Alzheimer's.
"This is an early indication that nutrition can affect brain biology at a molecular level, opening a non-drug avenue for protecting cognitive function as we age," she explained.
Shai noted that the research team wanted to test whether an enhanced Mediterranean diet, more plant-based and richer in polyphenols but lower in red and processed meats, could actually succeed in slowing the brain's biological aging.
The Mediterranean green diet is based on increasing the intake of polyphenols—plant compounds that help fight inflammation and protect cells—found in walnuts, olive oil, red wine, tea, fruits, and vegetables.
One group of participants followed the traditional Mediterranean diet, rich in vegetables, using chicken and fish instead of red meat, while a third group only followed general healthy eating guidelines.
Polyphenols protect memory
Shai stated that the antioxidant compounds "EGCG" in green tea, along with the healthy fats and polyphenols in walnuts, are likely the primary drivers of this change, while the "Mankai" plant provided additional support through the gut-brain axis and metabolic pathways.
She added that finding "Mankai" might be more difficult, but green tea and walnuts showed the most benefit, meaning most people can achieve similar benefits by focusing on just these two ingredients without special components.
"Mankai" has garnered researchers' attention for its dense nutritional value, as it is a source of complete plant protein and contains vitamin B12 and iron in forms that are easily absorbed by the body.
Previous studies by the same team had linked "Mankai" to improved blood sugar control, better metabolism and gut health, and reduced inflammation—all factors that can influence brain health and cognitive function.
"When we designed the Mediterranean green diet, we were looking for a new type of plant—something unfamiliar to the Western gut microbiome. It appears that introducing this novel plant, originally from the Far East, elicited a stronger microbial and metabolic response than we had anticipated," said Shai.
These findings come from the "DIRECT PLUS" trial, which spanned 18 months, and is one of the longest studies to examine the relationship between nutrition and brain health.
Although most participants were men with obesity or high cholesterol, necessitating further studies to see if the results also apply to women and healthier populations, the data add to the growing body of evidence suggesting that increasing plant-based food intake and reducing red and processed meats may help slow brain aging.
The researchers hope that proteins like "galectin-9" could one day be used in blood tests to detect early risks related to brain health.
However, they point out that the results are preliminary and do not prove that this diet prevents Alzheimer's or stops cognitive decline.
Jennie Finckki, a Connecticut-based dietitian specializing in metabolic health who was not involved in the study, said: "Based on these results, it's reasonable to think that green tea and Mankai can lower markers associated with neurodegeneration, but we still need more human trials that measure actual cognitive outcomes."
She added in comments to Fox News: "Green tea provides antioxidants, while walnuts offer healthy fats including omega-3, and both can be incorporated into a midday snack or an afternoon supporting meal to boost metabolic health and leverage their anti-inflammatory properties."
Finckki also advised limiting red meat consumption to a maximum of twice a week.
"True, these changes won't cause a complete brain overhaul in one week, but over time they can support brain health as part of a balanced diet," she concluded.
