Polyphenol-rich Mediterranean diets could help keep the brain younger

A new study suggests that Mediterranean and green-MED diets, rich in polyphenols from sources such as green tea and Mankai, may slow brain aging and reduce neurodegeneration. Blood sugar control plays a key role in maintaining brain volume.

Study: 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. Image credits: Pacorpi/Shutterstock.com

From a recent study published in The American Journal of Clinical Nutritionscientists examined how specific dietary factors affected brain volume in relation to chronological age.

Using longitudinal data, they examined the effects of the Mediterranean and green Mediterranean diets on hippocampal occupancy to assess brain aging and determine whether improved glycemic control could improve brain health.

Background

The brain undergoes a natural process of shrinkage or atrophy with age, which is also linked to cognitive decline with advancing age. Although the natural rate of brain atrophy with age is inevitable, certain diseases and conditions, such as type 2 diabetes, inflammation, high cholesterol and high blood pressure, can accelerate the rate of cognitive impairment and brain atrophy.

Type 2 diabetes has been linked to significant brain atrophy, especially in the hippocampus, which is critical for memory and is also affected by Alzheimer’s disease. Individuals with a long history of diabetes often exhibit enlarged brain ventricles and a greater degree of brain atrophy, indicating possible cognitive decline.

The measurement of the shrinkage of the hippocampus relative to the enlargement of the ventricles, known as the hippocampal occupancy score, has been used to monitor the risk of progression from mild cognitive impairment to Alzheimer’s disease.

Although recent studies have reported that healthy diets such as the Mediterranean diet can slow age-related brain volume loss, the impact of specific dietary changes, such as improved glycemic control, on brain health remains unclear.

About the study

The current study was based on a previous randomized control trial of nutritional interventions, known as the 18-month DIRECT PLUS study, which was conducted in the workplace and included nearly 300 participants over the age of 30.

The participants all had dyslipidemia or abdominal obesity and were randomly assigned to one of three dietary intervention groups. The health and nutrition guidelines group was the control group, while the other two groups were for the calorie-restricted Mediterranean diet intervention and the green Mediterranean diet intervention, which included a diet rich in polyphenols.

The Mediterranean diet emphasizes the consumption of poultry, fish and vegetables, while reducing red meat intake. Both Mediterranean diet interventions contain 28 grams of walnuts per day.

The green Mediterranean diet focused on polyphenol-rich foods, such as 3 to 4 cups of green tea per day and a Mankai green shake made from duckweed.

In addition, each group also received specific nutritional guidance and physical activity instructions, and each participant received a gym membership and attended regular instructional sessions on exercise and nutrition.

At the beginning and end of the study, various anthropometric and clinical measurements were recorded, including blood pressure, weight, height, waist circumference and fasting blood samples to assess the levels of glucose, insulin, hemoglobin A1c (HbA1c), C-reactive protein. and lipids.

Brain MRI scans were also performed at the start and end of the trial.

The researchers used specialized software to measure hippocampal and lateral ventricular volumes from the MRI scans, which were used to calculate the hippocampal occupancy score.

This measure served as the primary marker to assess neurodegeneration. Several statistical analyzes were performed to determine the relationship between the dietary interventions and changes in the hippocampal occupancy score.

Results

The study found that the Mediterranean diet, rich in polyphenols, resulted in improved glycemic control after an 18-month nutritional intervention, and these changes were associated with beneficial effects on brain aging. The green Mediterranean diet was associated with slower age-related neurodegeneration and younger brain age.

In contrast, simple weight changes had no pronounced impact on brain aging compared to changes in glycemic control, suggesting that better glycemic control provides an independent benefit to brain health.

The participants with lower body mass index, weight, HbA1c levels and blood pressure at baseline showed more favorable hippocampal occupancy scores.

Furthermore, those who showed significant improvements in fasting glucose, insulin resistance, HbA1c and C-reactive protein levels after 18 months of nutritional intervention also showed the most significant improvements in brain aging metrics.

The green Mediterranean diet, which included Mankai shakes and green tea, resulted in the highest glycemic improvement rate (58.33%). This diet has also been linked to notable benefits for brain health.

Increased consumption of green tea and Mankai shake was linked to greater improvements in brain health, especially in participants who consumed Mankai shake at least three times a week and drank green tea daily.

Conclusions

Overall, the study found that a healthy diet, such as the Mediterranean diet, low in red meat and rich in fruits, vegetables and lean meats, can support brain health by slowing age-related brain atrophy.

These findings also highlighted the potential of polyphenol-rich foods in reducing age-related neurodegeneration, making them a promising strategy for future cognitive health interventions.