Researchers studied 294 people to see if eating certain foods could help keep brains younger. They found that two proteins in the blood—Galectin-9 and Decorin—appear to be connected to faster brain aging. The good news? People who followed a special Mediterranean diet loaded with green tea, walnuts, and a plant called Mankai (while eating less red meat) showed lower levels of these proteins after 18 months. This suggests that what you eat might actually help your brain stay younger longer, though more research is needed to confirm these findings.

The Quick Take

  • What they studied: Whether eating a special Mediterranean diet could change proteins in the blood that are linked to brain aging, and if these changes could make brains age more slowly.
  • Who participated: 294 adults were divided into three groups: one eating standard healthy guidelines, one eating Mediterranean diet with walnuts, and one eating a green Mediterranean diet with even more plant foods, green tea, and walnuts while avoiding red and processed meat.
  • Key finding: People who followed the green Mediterranean diet had lower levels of a protein called Galectin-9 after 18 months compared to those eating standard healthy foods. This protein appears to be linked to faster brain aging, so lower levels may mean slower brain aging.
  • What it means for you: Eating more plant-based foods, green tea, and walnuts while limiting red and processed meat may help keep your brain younger. However, this is early research, and you should talk to your doctor before making major diet changes, especially if you have health conditions.

The Research Details

This was a secondary analysis of a larger study called DIRECT PLUS, which lasted 18 months. Researchers took blood samples from 294 participants and measured 87 different proteins in their blood. They also used special brain imaging (MRI scans) to calculate each person’s ‘brain age’—essentially how old their brain appeared compared to their actual age. The researchers then looked at whether the three different diets affected the levels of proteins in the blood and whether these changes matched up with changes in brain aging.

The three diet groups were: 1) Standard healthy eating guidelines, 2) Mediterranean diet with extra walnuts, and 3) Green Mediterranean diet with even more plant foods, green tea, walnuts, and a plant called Mankai, while eating less red and processed meat. By comparing blood proteins and brain imaging at the start and end of the study, researchers could see if diet changed the proteins linked to brain aging.

This approach is important because it looks at actual biological markers (proteins in the blood) that might explain how diet affects brain aging. Rather than just asking people about their diet and memory, researchers measured real changes in the body. The brain imaging also provided objective evidence of brain aging, making the results more reliable than studies based only on self-reported information.

This study has several strengths: it included a decent number of participants (294), used objective brain imaging rather than guesswork, measured many proteins to find patterns, and had a control group eating standard healthy foods for comparison. However, the study only lasted 18 months, so we don’t know if benefits continue longer. Also, this is a secondary analysis, meaning researchers looked at data collected for a different purpose, which can sometimes limit what conclusions we can draw.

What the Results Show

At the beginning of the study, researchers found that people with lower weight, smaller waist measurements, lower blood pressure, and better blood sugar control tended to have brains that appeared younger than their actual age. More importantly, people with higher levels of two proteins—Galectin-9 and Decorin—had brains that appeared older than expected.

After 18 months, something interesting happened: people whose brains aged more slowly had significantly lower levels of Galectin-9 in their blood. In contrast, people whose brains aged faster had higher levels of Decorin. This suggests these proteins might be markers of brain aging.

The most striking finding involved diet: people who followed the green Mediterranean diet (with lots of plants, green tea, walnuts, and less red meat) had the biggest drop in Galectin-9 compared to people eating standard healthy foods. This suggests the green Mediterranean diet may have been the most effective at lowering this protein linked to brain aging.

The study also found that at baseline, people with better metabolic health markers (like lower blood pressure and better blood sugar control) tended to have younger-appearing brains. When researchers looked at patterns across all 87 proteins measured, they found that the green Mediterranean diet created the most beneficial changes in the overall protein profile compared to standard healthy eating guidelines. This suggests the diet’s benefits might come from multiple proteins working together, not just one or two.

Previous research has suggested that Mediterranean diets are good for brain health, but this study adds new information by identifying specific proteins that might explain why. The focus on polyphenols (natural plant compounds found in green tea, walnuts, and Mankai) is relatively new and suggests that the type of plant foods matters, not just eating plants in general. The finding that a ‘green’ version with more plant compounds was better than a standard Mediterranean diet is a new insight.

This study has several important limitations to keep in mind. First, it only lasted 18 months, so we don’t know if the benefits continue or fade over time. Second, the study looked at proteins in the blood, but we’re not completely certain these proteins directly cause brain aging or if they’re just markers of it. Third, this was a secondary analysis, meaning the original study was designed for different purposes. Fourth, the study didn’t include very diverse populations, so results might not apply equally to everyone. Finally, while 294 people is a reasonable number, larger studies would give us more confidence in the findings.

The Bottom Line

Based on this research, eating a Mediterranean diet rich in plant foods, green tea, and walnuts while limiting red and processed meat may support brain health (moderate confidence level). However, this is early research, and more studies are needed. If you’re interested in trying this diet, start by gradually adding more plant-based foods and green tea to your meals, and reduce red and processed meat intake. Talk to your doctor first, especially if you have health conditions or take medications that might interact with dietary changes.

This research is most relevant for middle-aged and older adults concerned about brain health and aging. It may be especially interesting for people with family histories of cognitive decline or dementia. However, the findings don’t mean you must follow this diet—many factors affect brain health, including exercise, sleep, social connections, and mental stimulation. People with certain health conditions (like those requiring specific protein intake) should consult their doctor before making major dietary changes.

Based on this study, changes in blood protein levels appeared within 18 months. However, you likely won’t notice dramatic changes in how you feel or think in that timeframe. Brain health benefits from diet typically develop gradually over months and years. Think of it like building a savings account—small, consistent deposits add up over time. You might notice improved energy, mood, or focus within weeks or months, but the deeper brain-protective benefits probably take longer to develop.

Want to Apply This Research?

  • Track daily servings of plant-based foods (goal: 5+ servings), cups of green tea consumed (goal: 1-2 cups), weekly walnut intake (goal: 1 ounce or small handful most days), and red/processed meat meals (goal: reduce to 1-2 times per week). Use the app to log these specific foods and see weekly trends.
  • Start by replacing one red meat meal per week with a plant-based alternative, adding one cup of green tea to your daily routine, and including a small handful of walnuts as a snack. Use app reminders for green tea times and meal planning features to help incorporate more plant foods. Gradually increase these amounts over several weeks.
  • Use the app to track your diet quality score based on Mediterranean diet principles over 8-12 week periods. Set reminders for green tea consumption and plant-based meal planning. Consider periodic check-ins (every 3 months) to assess energy levels, mental clarity, and mood as indirect indicators of brain health. If possible, discuss with your doctor about periodic cognitive assessments to track any changes in memory or thinking.

This research is preliminary and should not replace professional medical advice. The study measured protein markers and brain imaging but did not directly measure cognitive function or dementia risk. Individual results may vary based on genetics, overall lifestyle, and health status. Before making significant dietary changes, especially if you have existing health conditions, take medications, or have concerns about brain health, consult with your healthcare provider or a registered dietitian. This research suggests associations between diet and brain aging markers, but does not prove that diet changes will prevent cognitive decline or dementia. Always seek personalized medical advice for your specific situation.