A large new study confirms that sticking to the Mediterranean diet — fish, poultry, vegetables and fruit, with minimal dairy foods and meat — may be good for the brain.

Researchers prospectively followed 17,478 mentally healthy men and women 45 and older, gathering data on diet from food questionnaires, and testing mental function with a well-validated six-item screening tool. They ranked their adherence to the Mediterranean diet on a 10-point scale, dividing the group into low adherence and high adherence. The study was published April 30 in the journal Neurology.

During a four-year follow-up, 1,248 people became cognitively impaired. But those with high adherence to the diet were 19 percent less likely to be among them. This association persisted even after controlling for almost two dozen demographic, environmental and vascular risk factors, and held true for both African-Americans and whites.

The study included 2,913 people with Type 2 diabetes, but for them adherence to the diet had no effect on the likelihood of becoming impaired.

The lead author, Dr. Georgios Tsivgoulis, an assistant professor of neurology at the University of Athens, said that this is the largest study of its kind. The Mediterranean diet, he added, “has many benefits — cardiovascular, cancer risk, anti-inflammatory, central nervous system. We’re on the tip of the iceberg, and trying to understand what is below.”