If you’re looking for a heart-healthy eating plan, the Mediterranean diet is probably a good fit, blending the basics of healthy eating with the traditional flavors and cooking methods of the Mediterranean.

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Two new studies recently took a closer look at the diet, discovering that those who closely follow it can reduce their risk of cognitive impairment by half by taking advantage of the diet’s strong emphasis on vegetables, whole grains, fish, and olive oil.

“People with the higher adherence to the Mediterranean diet had almost a 45% to 50% reduction in the risk of having an impaired cognitive function,” said lead author Dr. Emily Chew, who directs the Division of Epidemiology and Clinical Applications (DECA) at the National Eye Institute in Bethesda, Maryland.

Closely following the diet was defined as eating fish twice a week and regularly consuming fruits, vegetables, whole grains, nuts, legumes, and olive oil while reducing consumption of red meat and alcohol. The risk for cognitive decline increased as the levels of adherence dropped, Chew said.

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The Mediterranean diet didn’t appear to slow cognitive decline in people with the ApoE gene, which dramatically raises the risk for Alzheimer’s disease, Chew said. But when the study looked at just the levels of fish consumption, eating fish twice a week did slow the decline in people with the gene.

“In this study, while the Mediterranean diet overall decreased risk, the strongest factor to really move the needle was regular fish consumption,” said Dr. Richard Isaacson, who directs the Alzheimer’s Prevention Clinic at New York-Presbyterian’s Weill Cornell Medicine Center.

Chew and her colleagues examined data previously collected by two massive clinical trials called AREDS and AREDS2. Both examined nutritional supplements as a potential treatment for age-related macular degeneration, a progressive eye disease causing blurred vision and vision loss.

These studies included information about the participants’ diet and assessed their cognitive function periodically over five- and ten-year periods, respectively. The researchers also asked participants to report how often they consumed nine components of the Mediterranean diet.

“The retina is an extension of the brain,” Chew said. “A third of your brain functions for vision and the retina lines the eyeball and travels back via an optic nerve all the way to the brain.” That’s why it made sense that any antioxidants which might improve the retina might also improve the brain,” she said.

The researchers’ new evaluation shows that participants who stuck closest to the Mediterranean diet had the lowest risk of cognitive impairment. Eating lots of fish and vegetables appeared to have the greatest protective effect. At the 10 year mark, participants with the highest fish consumption had the slowest rate of cognitive decline.

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That’s because of two important antioxidants that are not naturally produced in the body: lutein and zeaxanthin. Responsible for the bright colors of vegetables, lutein and zeaxanthin are found in all vegetables, but especially good sources are green, leafy vegetables such as kale, parsley, spinach, broccoli, and peas.

Achieving some of these potential brain benefits doesn’t require a total diet overhaul. Radically changing what one eats is a complicated task, shaped by economic factors and social pressures, Chew points out. Instead of a total overhaul, she suggests making small changes.

The new studies, however large, are also observational, so more work is needed to definitively link this diet to cognitive preservation. Previous research has linked the diet to a wide array of benefits, from being good for heart disease to reducing the effects of air pollution.

The studies were published in the journal Annals of Neurology.