A green Mediterranean diet, high in polyphenols and low in red and processed meat, seems to slow age-related brain atrophy, according to a new BGU-led international study. The DIRECT PLUS 18-month long randomized control trial among ~300 participants is one of the longest and largest brain MRI trials in the world.
Their findings were published yesterday (Tuesday) in The American Journal of Clinical Nutrition.
The effect of diet on age-related brain atrophy is largely unproven. Participants were divided into three groups according to diet, and whole brain MRI measurements were taken before, and after the trial. Hippocampal-occupancy (HOC) and lateral-ventricle-volume (LVV) were measured as indicators of brain atrophy and predictors of future dementia. Brain MRI-derived data were quantified and segmented using NeuroQuant, an FDA (Food and Drug Administration) authorized fully automated tool.
Two hundred eighty-four men and women (88% men) aged 31-82 were randomly divided into three groups: A healthy dietary guidelines group, a Mediterranean diet group and a green Mediterranean diet. In the Mediterranean diet group, the participants were further provided walnuts rich in polyphenols. In the green- Mediterranean group the participants were further provided high polyphenol green components: 3-4 daily cups of green tea and a daily green shake of Mankai duckweed, as a substitute for dinner, with minimal consumption of red and processed meat. In addition, all three groups participated in physical activity programs based on aerobic exercise, including free gym memberships.
The trial was performed by Dr. Alon Kaplan and Prof. Iris Shai (pictured below), professor at Ben-Gurion University, Israel, and adjunct professor at Harvard University, together with several international teams of brain experts. The researchers were surprised to identify dramatic changes in MRI-related brain atrophy within 18-24 months, whereas the rate of brain atrophy markers (i.e., hippocampal occupancy decline and lateral ventricle volume expansion) were significantly accelerated from the age of 50 years and up.
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The researchers discovered a significant attenuation in brain atrophy over the 18 months in those who adhered to both Mediterranean diets; with greater magnitude in the green-MED group, specifically among participants over age 50. In addition, the researchers noticed that an improvement in insulin sensitivity was independently associated with attenuated brain atrophy.
Greater Mankai, green tea, and walnuts consumption and less red and processed meat consumption were significantly associated with lower hippocampal occupancy decline.
Participants were initially chosen based on abdominal girth size or dyslipidemia. They were all employees at a remote workplace in Israel (Nuclear Research Center in Dimona) where they did not leave the premises during the workday, and the lunch provided was monitored.
"The beneficial association between the green Mediterranean diet and age-related neurodegeneration might be partially explained by the abundance of polyphenols in plant-based food sources which have antioxidant and anti-inflammatory metabolites. Polyphenols can cross the blood-brain barrier (BBB), reduce neuroinflammation, and induce cell proliferation and adult-onset neurogenesis in the hippocampus," writes Prof. Shai, the lead author.
“Our findings might suggest a simple, safe, and promising avenue to slow age-related neurodegeneration by adhering to a green-Mediterranean diet," adds Dr. Alon Kaplan.
This study was funded by grants from the German Research Foundation (DFG), (project number 209933838 - SFB 1052; B11), Israel Ministry of Health grant 87472511; Israel Ministry of Science and Technology grant 3-13604; and the California Walnuts Commission.
None of the funding providers were involved in any stage of the design, conduct, or analysis of the study, and they had no access to the study results before publication.
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