A green-Mediterranean diet, high in phytochemicals called polyphenols and low in red and processed meat, seems to slow age-related brain atrophy, according to researchers from Israel. The DIRECT PLUS 18-month randomized control trial, which involved 284 participants with abdominal obesity, is one of the longest and largest brain MRI trials in the world.
About the study
Participants were divided into three diet groups, and whole brain MRI measurements were taken before and after the study. Specific areas of the brain were measured as indicators of brain atrophy and predictors of future dementia.
The participants, aged 31 to 82, were randomly divided into three groups: A healthy dietary guidelines group, a Mediterranean diet group and a green-Mediterranean diet group.
Both Mediterranean diets were calorie-restricted and included 28 g of walnuts (e.g., 14 walnut halves), which are high in polyphenols.
To boost polyphenols, the green-Mediterranean diet included four to five cups of green tea and a green shake each day. The shake included Mankai duckweed, a branded product containing a specific strain of duckweed, an aquatic plant also known as water lentils. Those in the green-Mediterranean diet group also further reduced their intake of processed and red meat.
All participants received free gym memberships and a program of aerobic and resistance exercise.
The findings
The researchers identified dramatic changes in MRI-related brain atrophy within 18-24 months, whereas the rate of brain atrophy markers was significantly accelerated from the age of 50 years and up.
They discovered a significant slowdown in brain atrophy over the 18 month trial in those who adhered to both Mediterranean diets. However a greater magnitude of protection was observed in the green-Mediterranean diet group, specifically among participants over age 50.
The study also found that an improvement in insulin sensitivity was independently associated with attenuated brain atrophy.
Greater Mankai duckweed, green tea and walnut consumption, as well as less red and processed meat consumption, were significantly associated with a lower decline in brain atrophy.
How the Mediterranean diet protects the brain
The beneficial effect of the Mediterranean diet on brain aging is thought to be due, at least in part, to its abundance of polyphenols, phytochemicals which have antioxidant and anti-inflammatory properties.
Polyphenols can cross the blood-brain barrier and have been shown to reduce nerve cell inflammation and stimulate an increase in brain cells.
“Our findings might suggest a simple, safe and promising avenue to slow age-related neurodegeneration by adhering to a green-Mediterranean diet,” said the lead researcher.
Source: American Journal of Clinical Nutrition, January 11, 2022.
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