Nutritional Pearls: Protecting the Mind With a Mediterranean Diet

Tom is a 40-year-old healthy man concerned about his risk of cognitive decline later in life. While he exercises regularly and maintains a healthy weight, he has always had trouble limiting his intake of “unhealthy foods.”

At a recent check-up, he asks if his diet could play any role in his risk of cognitive decline, and if so, what diets would help to “keep his mind sharp.”

How do you advise your patient?

(Answer and discussion on next page)

Dr. Gourmet is the definitive health and nutrition web resource for both physicians and patients with evidence-based resources including special diets for coumadin users, patients with GERD/acid reflux, celiac disease, type 2 diabetes, low sodium diets (1500 mg/d), and lactose intolerance.

Timothy S. Harlan, MD, is a board-certified internist and professional chef who translates the Mediterranean diet for the American kitchen with familiar, healthy recipes. He is an assistant dean for clinical services, executive director of The Goldring Center for Culinary Medicine, and associate professor of medicine at Tulane University in New Orleans.

Answer: Long-term adherence to a healthy diet, high in fruits, vegetables, legumes, low-fat dairy, fish, and whole grains is associated with lower risk of cognitive decline in older age.

I have mentioned before that a Mediterranean diet is a good way to reduce your risk of high blood sugars and diabetes and noted that its emphasis on more high-quality monounsaturated fats and less saturated fats was a good way to improve the quality of the fats in your diet. Now a study published in the journal Neurology looks at Mediterranean diet and its effects on cognitive function directly (2019;92(14):e1589-e1599).

The Research

The study included data from over 5000 healthy young men and women between the ages of 18 and 30 years from the CARDIA (Coronary Artery Risk Development in Young Adults) study, collected from 1985 to 1986.

At the start of the study and after 7 and 20 years, the participants responded to a detailed dietary questionnaire that allowed the authors to assign each person a score for how well they adhered to 3 different dietary patterns: the DASH (dietary Approaches to Stop Hypertension) diet; the Mediterranean diet; and APDQS (A Priori diet Quality Score), which takes into account higher intake of foods considered to be beneficial to health (such as legumes, vegetables, and fish) as well as lower intake of foods considered bad for health (such as fast food, desserts, high-fat dairy, and sugar-sweetened soft drinks).
Each participant thus had 3 scores for each diet: one representing their diet at the start of the study, one at the 7-year mark, and one at the 20-year mark. To take into account any changes in the individual's diet over time, the authors averaged the scores for each dietary pattern.

The participants also underwent a battery of 3 standardized test of cognitive function: one that tested verbal learning and memory, one that assessed processing speed, and a third that measured executive function. These cognitive tests were first performed at year 25 and were repeated, along with an additional test, at year 30.

For each individual, the authors created composite scores for each year's set of tests, then compared the two to see how the scores had changed over time. The individual's dietary pattern scores were then correlated with their cognitive scores to answer the question of which type of dietary pattern was (or was not) linked with changes in cognitive function over time.

The authors note that the participants' average Mediterranean diet and DASH diet scores tended to increase over the course of the study (20 years), while their APDQS decreased.

The Results

When considering changes in cognitive scores, the authors also took into account demographics (gender, race, income, etc.) as well as health factors such as smoking and caloric intake. They found that after taking those other factors into account, better Mediterranean diet scores and APDQS were linked to better initial scores in the cognitive function tests, while DASH diet scores didn't appear to be related either way.

The 5-year changes in cognitive function were similarly related to dietary pattern: "those with middle or high a Mediterranean diet or APDQS scores had less decline", said the authors, while a DASH diet was "not associated with 5-year change in global cognitive function."

What’s the Take Home?

The authors put it succinctly: "...greater long-term adherence to a Mediterranean diet or APDQS, but not DASH, was associated with less decline in global cognitive function in midlife."

But there are the typical caveats: this study shows correlation but does not prove that any particular dietary style caused decline or even protected the participants from cognitive decline. However, it's reasonable to add this study to the evidence that a Mediterranean style diet can protect your brain from cognitive decline.

Reference:

McEvoy CT, Hoang T, Sidney S, et al. Dietary patterns during adulthood and cognitive performance in midlife [published online March 6, 2019]. Neurology. doi: 10.1212/WNL.0000000000007243