This Diet May Slow Brain Aging, According to Study

Beth Ann Mayer

Wed, November 13, 2024 at 3:25 PM UTC

7 min read

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You've likely heard of the Mediterranean diet, which prioritizes fruits, vegetables, healthy fats, plant-based foods, and lean proteins. For seven years in a row, U.S. News & World Report has crowned it the No. 1 diet.

The Mediterranean diet has gained a research-backed reputation for lowering the risk of chronic diseases. However, a new study published in the American Journal of Clinical Nutrition in November found that a variation of the Mediterranean diet can improve blood sugar. The diet, known as the "Green Mediterranean diet," focuses more on polyphenols and encourages people to get these antioxidants through sources like mankai (an edible plant that grows in the water) and green tea.

"The study is unique because we in the nutrition world have a lot of data on the impact of the Mediterranean diet and chronic diseases, such as heart disease or diabetes," says Destini Moody, RD, CSSD, LD, a registered dietitian with Garage Gym Reviews.

However, we don't have a ton of information on how blood sugar and brain health can go hand in hand.

"Now, with these results, it forces people to start thinking about the impact of uncontrolled blood sugars and the inflammation it may cause beyond just diabetes and the associated comorbidities," Moody says.

Moody and other registered dietitians weighed in on what the study tells us about the Green Mediterranean diet, whether it's worth trying and tips for getting started.

What New Research Tells Us About the Green Mediterranean Diet and Brain Health

The study included 294 people over 30 years of age with abdominal obesity or high cholesterol levels. Most of them (88%) were men.

Kathleen Garcia-Benson, RDN, CSSD, LD, of Top Nutrition Coaching, explains that researchers split the participants into three groups:

One group followed regular healthy diet advice.
One group followed a calorie-restricted Mediterranean diet.
The third group followed the Green Mediterranean diet.

Um, what?

"The Green Mediterranean diet included three to four cups of green tea and a green shake made from duckweed, an aquatic plant, each day," Garcia-Benson says.

One 2021 Nutrients study found that mankai, which is in the duckweed family, could help the gut.

"Both the Mediterranean and Green Mediterranean groups also consumed one ounce of walnuts daily," Garcia-Benson adds. "The calorie intake for groups two and three was limited to 1,500 to 1,800 calories per day for men and 1,200 to 1,400 for women. The first group did not have calorie restrictions."

Researchers used brain MRIs to track brain changes. Garcia-Benson says they focused on the hippocampal occupancy score (HOC), a critical marker of brain aging.

"They found that participants in the Green Mediterranean group—especially those with better blood sugar control—showed less brain aging compared to other groups," Garcia-Benson says.

While the research on blood sugar and brain functioning may be under-studied, it's unsurprising to find a link.

"When we aren't consuming enough carbohydrates, the brain cannot properly function or communicate signals to the rest of the body," explains Maddie Pasquariello, MS, RDN.

However, Pasquariello says having chronically high blood glucose, an issue for people with diabetes, can also cause issues with memory and cognition.

"Persistently high blood glucose levels can ultimately be one factor contributing to brain atrophy and diseases that restrict blood flow to the brain, which increases one's likelihood of dementia," Pasquariello says.

The new research adds to a growing body of data, including a 2022 study, that Mediterranean and Green Mediterranean diets can reduce age-related brain atrophy (reduced brain cells or connections between brain cells).

"The Green Mediterranean diet is rich in powerful antioxidants to fight inflammation, and inflammation is one of the key factors of the development of neurodegenerative diseases next to genetics," Moody says. "Chronic inflammation also leads to the development of chronic diseases like diabetes."

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However, Garcia-Benson cautions that the new study had its limitations, including:

The outcomes cannot be solely attributed to polyphenol intake due to limited information on participants’ previous diets.
The study only used hippocampal occupancy score (HOC) to measure brain health; assessing other brain regions would provide a more full picture.
The participant pool was 88% male, which may limit how these results apply to females.
Calorie deficits in groups two and three may have influenced blood sugar control, as weight loss that may have occurred may play a role in enhancing insulin sensitivity.

Still, RD thinks the research is interesting and warrants further discussion and exploration.

"Nutrition research is slow and expensive, but in this case, the long study duration and high adherence rates were strengths," says Cara Harbstreet, MS, RD, LD of Street Smart Nutrition. "These results would need to be replicated in other studies, but it appears the diet interventions could be a low-risk and practical approach to supporting brain health as we age."

Tips for Brain-Healthy Eating and Following the Green Mediterranean Diet

1. Don't worry about following the Green Mediterranean diet

Hot take?

"My first tip would be to ignore the whole Green Mediterranean diet thing—yes, shocker given the results of this study, but hear me out," Pasquariello says. "Focus on the tenets described in the standard Mediterranean diet, and don't stress too much about exactly how much polyphenol content you're getting. Getting too granular with things misses the big picture and, for most people, is way more stress than it's worth."

The good news is that polyphenols are present in many items commonly included in the Mediterranean, including fruits, veggies and nuts, Pasquariello says.

Of course, if you like green tea, sip up.

2. Limit added sugar

Harbstreet suggests sticking to the guidelines to cap added sugar at 10% of your daily calories.

"Pick and choose which sweet foods you want to include," she says. "Remember that moderate amounts of low- and no-calorie sweeteners or sugar alternatives can help make this transition sustainable for the long term."

3. Aim for fiber-rich foods

Harbstreet says fiber-rich foods assist with blood sugar control and keep you feeling fuller for longer.

"Whole grains, beans, legumes, nuts and seeds, as well as fruits and vegetables, all contain a variety of other important nutrients," Harbstreet says. "This won’t necessarily replicate the diet used in this study, but it’s likely an improvement from your baseline if you haven’t already been including these foods very often."

Related: 17 High Fiber, Low Carb Foods

4. Go slow

If you're currently consuming a diet high in sugar and ultra-processed foods, Pasquariello suggests making gradual changes.

"Make one of your usual UPF snacks into a homemade or two-ingredient, whole-food snack instead," she says. "This is usually one of the simplest things to change for those of us who are on the go a lot or don't have a ton of time."

Some of her favorite ideas include:

An apple with nut butter
A yogurt cup with berries
Rice cakes with hummus
Carrots with tzatziki

"None of these things are super expensive, and a lot of them are easy enough for on-the-go and busy mornings," Pasquariello says.

Another easy-peasy snack idea? Walnuts, which was part of the current study.

Garcia-Benson suggests incorporating them into your daily diet.

"Walnuts are known for supporting brain health with their healthy fats and polyphenols," she says. "They're easy to snack on, add to oatmeal or yogurt, or pair with berries for a satisfying, brain-friendly snack that stabilizes blood sugar."

Up Next:

Sources:

Mediterranean Diet: Beginner's Guide to a Healthy Heart. U.S. News & World Report.
Glycemic control contributes to the neuroprotective effects of Mediterranean and green-Mediterranean diets on brain age: the DIRECT PLUS brain-magnetic resonance imaging randomized controlled trial. American Journal of Clinical Nutrition.
Destini Moody, RD, CSSD, LD, a registered dietitian with Garage Gym Reviews
The Metabolomic-Gut-Clinical Axis of Mankai Plant-Derived Dietary Polyphenols. Nutrients.
Maddie Pasquariello, MS, RDN
The effect of a high-polyphenol Mediterranean diet (Green-MED) combined with physical activity on age-related brain atrophy: the Dietary Intervention Randomized Controlled Trial Polyphenols Unprocessed Study (DIRECT PLUS). American Journal of Clinical Nutrition.
Cara Harbstreet, MS, RD, LD of Street Smart Nutrition

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