Heart-Healthy Diets May Also Protect Your Brain

“What you eat in midlife may matter for your brain health decades later,” says study author Kjetil Bjornevik, MD, PhD, an assistant professor of epidemiology and nutrition at Harvard University’s T.H. Chan School of Public Health in Boston.

“A diet rich in vegetables, fish, and whole grains — while limiting processed meats and sugary foods — is consistently linked to better cognitive outcomes, and these dietary patterns also tend to support blood pressure control.”

More Fish, Vegetables and Less Red or Processed Meats Linked to Better Cognition

Researchers set out to assess whether healthy dietary patterns were linked to a lower risk of cognitive decline.

The study included more than 150,000 participants, who were about 44 years old on average and mostly women. Participant diets were rated for how closely they resembled six healthy eating patterns.

The most well-known of these diets was the Dietary Approaches to Stop Hypertension (DASH) diet, a plant-focused eating style that can lower high blood pressure. Other diets included the Planetary Health Diet Index, which is an environmentally aware eating regimen, and specialized diets for lowering insulin and inflammation levels.

Researchers calculated diet “scores” (how closely participants followed a particular diet) using self-reported food frequency questionnaires collected every four years over about three decades.

Toward the end of the three-decade period, researchers assessed cognitive decline via participants’ own self-reported data.

For a subset of participants, researchers conducted phone interviews to objectively measure cognitive function with standardized testing.

Comparing the diet scores to cognitive measurements, the researchers concluded:

• All six healthy diets were linked to a lower risk of subjective cognitive decline.
• All diets except the plant-based diet index and planetary health diet index were linked to a higher objective cognitive function.
• Having a higher intake of fish and vegetables — and a lower intake of red and processed meats, fried potatoes, and sugary beverages —was linked to better objective cognitive function.
• The association with better cognitive function was strongest when healthy eating happened between the ages 45 to 54.

“What was encouraging was the consistency across different dietary patterns, which suggests that there is not just one right approach and that different dietary strategies can have beneficial effects on cognitive health,” Dr. Bjornevik says.

“More broadly, any dietary pattern that emphasizes vegetables, fish, and whole grains while limiting red and processed meats, fried foods, and sugary beverages aligns with what our findings suggest may be beneficial.”

Comparing Healthy Diets: What Stands Out About These Findings

“[Our study] reinforces that healthy dietary patterns are generally linked to better cognitive outcomes, and it highlights that the DASH diet — originally designed for blood pressure control — showed particularly strong and consistent associations with cognitive health,” Bjornevik says.

But what hadn’t been previously examined, the researchers said, was the effect of multiple healthy dietary patterns on cognitive health within the same context.

“Another important feature of this work is that diet was assessed repeatedly midlife,” Brandt adds, “long before the subjective and objective cognitive assessments. This makes it more likely that diet affects cognition rather than vice versa.”

It’s worth pointing out that the study was observational in nature and relied in part on self-reported cognitive changes, which can introduce room for error. In addition, though the sample size was large, the participants were predominantly white educated healthcare professionals, so it’s unclear whether the results could be broadly applied to the general population, Brandt adds.

Brandt also notes that subjective cognitive impairment — the participants’ personal sense of changes in their memory, attention, visual and spatial cognition, and executive function — was the focus of the study. Only a subset of people who were 70 or older and hadn’t had a stroke received the objective cognitive testing — which may not reveal the full picture around cognition.

For future areas of research, Bjornevik and the study authors recommend clinical trial testing into whether specific dietary interventions can slow cognitive decline.

What You Should Know About Healthy Eating and Cognitive Health

Rather than overhauling your entire diet at once, Bjornevik suggests focusing on gradually shifting toward more vegetables, fish, and whole grains while reducing processed meats, fried foods, and sugary beverages.

“Small, sustainable changes over time are more realistic and more likely to stick than dramatic changes,” he says.

• Try cooking without meat at least twice per week.
• Aim to have something green on your plate (think lettuce or cucumber) for most meals.
• Top oatmeal or cereal with sliced fresh fruit for breakfast.
• Make a salad or add sliced vegetables to your sandwiches for lunch.
• Reframe meat as being a part of your dinner, rather than the main course.
• Choose fresh fruit or low-fat frozen yogurt in place of sugary desserts.
• Opt for small portions of healthy snacks like nuts, yogurt, or dried fruit.

“Overall, though, the message is clear,” Brandt says. “Eating a heart-healthy, blood-pressure-lowering diet in midlife, along with other health-promoting behaviors (exercise, not smoking, staying cognitively and socially active) contributes to cognitive health as we age.”