Green-Mediterranean Diet Linked to Slower Brain Aging in Harvard and Ben-Gurion Study
A new study has found that the green-Mediterranean diet—a plant-focused variation of the classic Mediterranean diet—may help slow down brain aging. Conducted by researchers from Ben-Gurion University of the Negev, the Harvard T.H. Chan School of Public Health, and the University of Leipzig, the study has revealed that this dietary pattern influences specific proteins in the blood that are tied to accelerated brain aging.
Published in Clinical Nutrition in August 2025, the research adds an important layer of evidence showing how diet can directly shape brain health and potentially reduce risks of cognitive decline.
What Exactly Is the Green-Mediterranean Diet?
The traditional Mediterranean diet is already well known for its benefits, including reduced risk of cardiovascular disease, better metabolic health, and improved longevity. It focuses on vegetables, legumes, fruits, whole grains, olive oil, and moderate amounts of poultry and fish, while limiting red and processed meats.
The green-Mediterranean diet (green-MED) takes it a step further by adding polyphenol-rich foods and reducing red and processed meat intake even more. The three main additions are:
- Walnuts – a rich source of healthy fats, polyphenols, and antioxidants.
- Green tea – loaded with catechins, compounds known for their anti-inflammatory and brain-protective effects.
- Mankai (duckweed) – a small aquatic plant, high in protein, iron, and bioactive compounds, including polyphenols.
By incorporating these foods daily, the diet boosts the intake of anti-inflammatory and antioxidant compounds, which may be key to its brain-protective effects.
The DIRECT PLUS Trial and Brain Health
This research is a secondary analysis of the DIRECT PLUS randomized controlled trial (NCT03020186), one of the most extensive long-term studies on diet and health. Around 294 participants were randomized into three groups over an 18-month period:
- A healthy dietary guidelines (HDG) group.
- A traditional Mediterranean diet group, enriched with moderate amounts of walnuts.
- The green-Mediterranean diet group, enriched with walnuts, green tea, and Mankai.
Participants were monitored closely for changes in health markers. What made this analysis unique is that the researchers focused on brain aging, using advanced tools like MRI scans and blood protein analysis to measure biological changes.
Measuring Brain Age – The Brain Age Gap (BAG)
To estimate how fast participants’ brains were aging, the researchers used whole-brain MRI scans at both the beginning and end of the study. These scans were analyzed with a convolutional neural network model, which predicts a person’s “brain age.”
The key measure here is the Brain Age Gap (BAG)—the difference between the predicted brain age and the participant’s actual chronological age. A higher BAG means the brain appears biologically older than the person’s real age, a sign often linked to neurological decline, mild cognitive impairment, and even Alzheimer’s disease.
By tracking BAG, researchers were able to directly measure how diet influences brain aging over time.
Proteins That Reveal Brain Aging
In addition to MRI scans, the study analyzed nearly 87 blood proteins using advanced proteomics technology (Olink CVD II panel). These proteins serve as biological signatures of inflammation, metabolism, and neurodegeneration.
Two proteins stood out:
- Galectin-9 (Gal-9) – Higher levels of this protein were strongly associated with accelerated brain aging.
- Decorin (DCN) – Levels of this protein rose in participants whose brain aging accelerated during the trial.
Interestingly, participants who showed slowed or attenuated brain aging during the trial had significant decreases in Gal-9 levels. On the other hand, rising Decorin levels were seen in those whose brain aging worsened.
How the Green-Mediterranean Diet Made a Difference
The study found that the green-MED group experienced a marked reduction in Galectin-9 levels, both compared to their own baseline and relative to the healthy-diet guideline group. This suggests that the diet actively shifts blood protein markers in a way that supports brain health.
The researchers also noted a strong interaction between the diet and proteomics principal component analysis (PCA)—in simpler terms, the green-MED diet created measurable, favorable changes in overall protein patterns linked to brain aging.
This provides evidence that diet can reshape our biological pathways in real time, creating a “younger” protein profile in the blood, which aligns with a slower aging brain.
Previous Findings on Brain Atrophy
This is not the first time the DIRECT PLUS trial has shown brain benefits. Earlier reports revealed that both the traditional Mediterranean and green-MED diets cut brain atrophy (shrinkage) by about 50% compared to the control group over the 18-month period. Brain atrophy is another well-established marker of cognitive decline and dementia risk.
Additionally, improvements in glycemic control—measured by reductions in blood sugar markers like HbA1c—were also linked to slower brain aging. This suggests that better blood sugar regulation could be one mechanism through which these diets protect the brain.
Why Polyphenols Matter
Polyphenols are plant-based compounds with strong antioxidant and anti-inflammatory properties. They help reduce oxidative stress and inflammation, both of which are key drivers of aging and neurodegeneration.
- Green tea catechins have been widely studied for their role in improving memory, attention, and overall brain health.
- Walnuts are not only rich in polyphenols but also in omega-3 fatty acids, both of which support brain cell membranes and reduce inflammation.
- Mankai (duckweed) is a lesser-known but nutrient-dense food. It contains high-quality protein, iron, vitamin B12 (rare in plants), and numerous bioactive compounds.
Together, these foods make the green-MED diet stand out from other dietary patterns.
How Brain Age Research Is Evolving
The concept of measuring brain age is gaining popularity in neuroscience. Instead of waiting for visible symptoms of dementia or cognitive decline, researchers are now able to look at biological aging markers decades earlier.
By combining MRI-based BAG measurements with blood proteomics, scientists get a more dynamic and real-time window into how lifestyle choices—like diet—impact brain health.
This opens new doors for personalized medicine, where doctors might one day use simple blood tests to predict brain health risks and recommend tailored lifestyle changes.
Broader Implications
The study provides compelling evidence that dietary interventions can preserve brain health and possibly prevent neurodegenerative diseases. For individuals, it reinforces the importance of dietary choices not only for heart health and longevity but also for protecting cognitive function.
It also raises exciting questions:
- Could dietary patterns rich in polyphenols delay or reduce the risk of Alzheimer’s disease?
- Will blood proteins like Galectin-9 and Decorin become routine biomarkers in future brain health check-ups?
- Could the green-MED diet be integrated into clinical recommendations for aging populations?
These are areas that will need more research, but the findings mark a significant step forward.
Limitations of the Study
While the results are promising, it is important to note the study’s limitations:
- It is a secondary analysis of an existing trial.
- The sample size was around 300 participants, which is large but not enough to generalize to all populations.
- The trial lasted 18 months, so long-term effects beyond this period are still unknown.
- More studies are needed in diverse populations to confirm the findings.
Still, the evidence is strong enough to suggest that dietary changes, especially those focusing on plant-based polyphenols, can make a measurable difference in brain aging.
Extra Knowledge: Other Diets and Brain Health
To give broader context, here are a few other dietary patterns that have been studied in relation to brain health:
- MIND Diet – A combination of the Mediterranean and DASH diets, specifically designed to reduce dementia risk. It emphasizes leafy greens, berries, nuts, olive oil, and limits butter, sweets, and fried foods.
- Ketogenic Diet – High in fats and low in carbohydrates, sometimes studied for neurological conditions like epilepsy and Alzheimer’s. However, its long-term safety and effects on brain aging are debated.
- Plant-Based Diets – Diets rich in whole, unprocessed plant foods have been linked to lower risks of cognitive decline, largely due to anti-inflammatory and antioxidant compounds.
The green-MED diet seems to combine the strongest aspects of these approaches: high polyphenols, reduced red meat, and nutrient-rich plant sources.
Conclusion
The new research shows that following a green-Mediterranean diet may not only improve metabolic and cardiovascular health but also slow down brain aging by directly influencing blood proteins tied to neurodegeneration. This is a fascinating development that points to the potential of nutrition as a powerful tool for protecting the brain as we age.
For anyone looking to maintain brain health, incorporating foods like green tea, walnuts, and Mankai while reducing processed and red meats might be one of the most practical, science-backed strategies available today.
