Can the Mediterranean Diet Delay or Prevent Dementia?

(Editor’s note: This article is part of an editorial partnership between Next Avenue and The American Federation for Aging Research (AFAR), a national nonprofit organization whose mission is to support and advance healthy aging through biomedical research.)

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Before earning her doctorate in public health nutrition from Queen’s University Belfast in 2012 and embarking on a research career there, registered dietitian Claire McEvoy spent a decade working in clinical nutrition for the National Health Service in Northern Ireland.

That experience, “supporting people to make appropriate and evidence-based dietary choices has completely influenced the type of research I do,” she says. McEvoy studies how different types of dietary habits in people affect their health and “healthspan,” which means the number of years of good health humans can enjoy toward the end of life.

As a 2015 recipient of the American Federation for Aging Research’s Paul B. Beeson Emerging Leaders Career Development Award in Aging, McEvoy has focused her fellowship research on the Mediterranean diet and other healthy dietary habits.

She says she wants “to increase our knowledge on how diet contributes to cognitive health during aging, and to understand how best we can support dietary behavior change at different life stages to improve health and well-being. Ultimately, my goal is to identify effective dietary strategies to prevent and treat cognitive disorders during aging.”

McEvoy and other AFAR-supported researchers are driving discoveries that move us closer to extending healthspan.

In addition to regular columns by AFAR’s Scientific Director Steven N. Austad, AFAR is excited to share insights from the field of aging research through this “Ask the Expert” interview (previous interviews have addressed age-related dementia research, cancer research and the effects of younger blood on aging).

AFAR recently talked with McEvoy about the link between nutrition and cognitive decline, and the implications of her research for Alzheimer’s disease and other dementias, and healthy aging.

AFAR: What should people know about the link between diet and brain health, especially as it relates to the Mediterranean diet and healthy aging?

Claire McEvoy: It’s generally believed that what’s good for the heart is good for the brain, and that is why most research into diet and brain health to date has focused on the traditional Mediterranean diet.

It’s proven to be effective for reducing both primary and secondary cardiovascular disease and has also shown clinically significant benefits for several cardiovascular disease risk factors, such as cholesterol profiles, high blood pressure, fasting glucose level and inflammatory biomarkers, which are also risk factors for cognitive decline.

The traditional Mediterranean diet is plant-based, rich in fruit and vegetables, whole grains, legumes and moderate in fish and nuts. It also includes alcohol that tends to be consumed with meals. This diet is generally low in processed foods, sugary foods and red meat.

Observational evidence, while inconsistent, tends to support the Mediterranean diet for brain health as well as cardiovascular health.

However, the effects of this diet’s changes on cognitive function have been tested in few intervention studies. Preliminary results have shown improvement in cognitive function for people who are at high risk of developing cardiovascular disease.

Some research has focused on single nutrients, like vitamin E, or B vitamins. Very often, however, the evidence is mixed, likely because of differences in the types of populations studied and the diverse nature of vitamin supplements tested.

Some people with nutrient deficiencies may experience cognitive benefit from vitamin supplements. However, most people in the general population will derive greater health benefits from improving the quality of their regular diet rather than relying on vitamin supplements.

In two recent studies, you looked at how different types of dietary habits, including the Mediterranean diet, affect cognitive function in older adults and people in midlife. What are the most important takeaways so far?

We investigated the Mediterranean diet in the well-known Health and Retirement Study and the Coronary Artery Risk Development In Young Adults (CARDIA) study and found that greater adherence to the this way of eating was associated with better cognitive health in both older and younger adults.

In the most recent study conducted with Dr. Kristine Yaffe and other CARDIA investigators, the most important take-home message is that maintaining healthy dietary practices that align with the Mediterranean diet during young adulthood can help to preserve cognitive function even at midlife.

That is an important point. Because diet is likely to provide subtle, but cumulative, protective effects on brain health throughout a person’s lifetime that help to reduce the risk of, or at least slow down, cognitive decline as we get older, and potentially help to delay dementia in late life.

What are some of the key points research is revealing about the science behind the health benefits of the Mediterranean diet?

In our dietary analyses, we’ve found that individual foods on their own tend to have weaker associations with health outcomes compared with overall dietary habits. Therefore, while single foods and nutrients may be important, the combination of foods and nutrients within a person’s diet can act together to have greater biological effects.

In addition, we’re beginning to understand more about the mechanisms of how a healthy diet, such as the Mediterranean diet, affect brain health. These insights come from a range of studies in both animals and humans. The Mediterranean diet may have a beneficial impact on cognitive health because it improves our vascular health.

The Mediterranean diet and other high-quality diets also have antioxidant and anti-inflammatory effects that could protect against cognitive decline and dementia.

Your current research would seem to have larger implications regarding nutrition and healthy aging. Where do you think this might lead?

I am very much a public health researcher, so I want to help inform dietary recommendations that will benefit brain health throughout a person’s life to prevent or delay Alzheimer’s disease and dementia. The Mediterranean diet is clearly an important dietary pattern for overall healthy aging. But it should be emphasized that we don’t yet know the optimal combination of foods and nutrients for brain health.

One of the most interesting aspects of diet is that it has the potential to influence the development of several diseases, including obesity, diabetes, cardiovascular disease and some types of cancer.

Addressing poor-quality diets and diet-related disease in our population should be a major policy focus for healthy aging. While it is important to generate robust evidence of 'what works,' a key challenge going forward will be to find effective ways to promote and support healthy dietary habits in people for disease prevention and healthy aging.