The study, published in Neurology, set out to test whether higher adherence to a Mediterranean-type diet is linked to bigger brain volumes, and better maintenance of brain size during the ageing process.
Led by Yian Gu from Columbia University in New York, the team scanned the brains of more than 650 people – finding that those whose diets included at least five out of nine measures of a healthy Mediterranean style diet had brain volumes that were larger than the brain volumes of people whose diets included fewer than five components.
“These results are exciting, as they raise the possibility that people may potentially prevent brain shrinking and the effects of ageing on the brain simply by following a healthy diet,” said Gu
Indeed, they revealed that, on average, grey matter volume was 5 millilitres greater and white matter 6.4 millilitres greater than those who did not include at least five components.
According to the team, this difference in brain size is the equivalent to about five years of shrinkage through ageing.
“The magnitude of the association with brain measures was relatively small,” added Gu. “But when you consider that eating at least five of the recommended Mediterranean diet components has an association comparable to five years of age, that is substantial.”
Gu and coleagues performed a cross-sectional study, in which high-resolution structural MRI was collected on 674 elderly adults without dementia, and a mean age of 80 years.
Dietary information was collected via a food frequency questionnaire, which assessed whether the participants' diets during the past year included any of the following nine components of the Mediterranean diet: eating lots of vegetables, legumes, cereals, fish, fruits and nuts; consuming healthy monosaturated fats like olive oil but avoiding saturated fats; drinking moderate amounts of alcohol; and eating low amounts of meat and dairy products.
Total brain volume (TBV), total gray matter volume (TGMV), total white matter volume (TWMV), mean cortical thickness (mCT), and regional volume or CT were taken via MRI scans.
The team reported that people who followed a diet that involved at least five of the nine measures of a healthy Med style diet had a brain size that was, on average, 13.11 millilitres greater than that of those who did not match up with at least five of the markers.
When the researchers took a closer look at the relationship between brain shrinkage and the Mediterranean diet, they found that the protective effect was driven to the greatest extent by two components: consuming more fish and eating less meat.
“Eating at least 3 to 5 ounces of fish weekly, or eating no more than 3.5 ounces of meat daily, may provide considerable protection against loss of brain cells equal to about three to four years of ageing,” said Gu.