Unhealthy foods spoil the benefits of a Mediterranean diet

In a new study from Rush University Medical Center, experts report that unhealthy foods may offset the positive effects of an otherwise healthy diet. More specifically, the researchers found that eating foods high in sugar and fat diminished the cognitive benefits of a Mediterranean diet.

Dr. Puja Agarwal is a nutritional epidemiologist and assistant professor in the Department of Internal Medicine at Rush Medical College.  

“Eating a diet that emphasizes vegetables, fruit, fish and whole grains may positively affect a person’s health,” said Dr. Agarwal. “But when it is combined with fried food, sweets, refined grains, red meat and processed meat, we observed that the benefits of eating the Mediterranean part of the diet seems to be diminished.”

In older adults, a Mediterranean diet is associated with slower rates of cognitive decline. The study was focused on 5,001 older adults living in Chicago who participated in the Chicago Health and Aging Project, which evaluated the individuals’ cognitive health from 1993 to 2012. 

Every three years, the participants completed a cognitive assessment and answered questions about the frequency with which they consumed 144 food items.

The researchers analyzed the diet of each individual, noting how closely the participants adhered to a Mediterranean diet. This diet includes daily consumption of fruit, vegetables, legumes, olive oil, fish, potatoes, unrefined cereals, and moderate wine consumption. 

The team also assessed how much each individual followed a Western diet, including fried foods, red meat, sugary foods, pizza, full-fat dairy products, and processed meats. Based on the data, the participants were assigned Mediterranean diet scores ranging from zero to 55.

Next, the researchers examined the association between Mediterranean diet scores and changes in cognitive function, episodic memory, and perceptual speed. 

The study revealed that participants with slower cognitive decline over the years of follow-up were those who adhered closest to the Mediterranean diet while limiting foods that are part of Western diet. On the other hand, people who ate more of the Western foods did not experience the cognitive benefits of the healthier foods.

“Western diets may adversely affect cognitive health,” said Dr. Agarwal. “Individuals who had a high Mediterranean diet score compared to those who had the lowest score were equivalent to being 5.8 years younger in age cognitively.”

According to Dr. Agarwal, the results complement other studies showing that a Mediterranean diet reduces the risk of heart disease, certain cancers, and diabetes. The findings also support previous studies on Mediterranean diet and cognition. 

“The more we can incorporate green leafy vegetables, other vegetables, berries, olive oil, and fish into our diets, the better it is for our aging brains and bodies. Other studies show that red and processed meat, fried food and low whole grains intake are associated with higher inflammation and faster cognitive decline in older ages,” said Dr. Agarwal. “To benefit from diets such as the Mediterranean diet, or MIND diet, we would have to limit our consumption of processed foods and other unhealthy foods such as fried foods and sweets.”

The study is published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

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By Chrissy Sexton, Earth.com Staff Writer