Switching to a green Mediterranean diet, with a daily intake of walnuts, green tea and lower red/processed meat, can have a positive effect on brain health, and slow brain ageing, according to new research.

The green Mediterranean includes a daily intake of walnuts (28 grams), 3-4 cups of green tea and a cup of Wolffia-globosa (Mankai) plant green shake of duckweed per day over 18 months. The aquatic green plant Mankai is high in bioavailable iron, B12, 200 kinds of polyphenols and protein, and is, therefore, a good substitute for meat.

Obesity has been linked with the brain ageing faster than would normally be expected.

The findings, published in the journal eLife, showed that a reduction in body weight of 1 per cent, due to the consumption of a green Mediterranean diet, led to the participants' brain age being almost 9 months younger than the expected brain age after 18 months.

This attenuated ageing was associated with changes in other biological measures, such as decreased liver fat and liver enzymes.

Increases in liver fat and the production of specific liver enzymes were previously shown to negatively affect brain health in Alzheimer's disease.

Researchers at the Ben-Gurion University of the Negev in Israel studied 102 individuals who met the criteria for obesity. They used the brain scans taken at the start and end of the study to examine the impact of lifestyle intervention on the ageing trajectory.

"Our study highlights the importance of a healthy lifestyle, including lower consumption of processed food, sweets, and beverages, in maintaining brain health," said Dr. Gidon Levakov, from the varsity's Department of Cognitive and Brain Sciences.

"We were encouraged to find that even a weight loss of 1 per cent was sufficient to affect brain health and lead to a 9-month reduction in brain age," added Prof. Galia Avidan of the Department of Psychology.

With global rates of obesity rising, identifying interventions that have a positive impact on brain health could have important clinical, educational, and social impacts, the researchers said.