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It’s the combined effect of the Mediterranean dietary pattern that counts toward maintaining cognitive health, not its individual foods.

Ivo Gretener/iStockPhoto / Getty Images

Scan a list of “brain foods” and you’re bound to find blueberries, fish and leafy greens on it. These specific foods have been linked to improved memory, concentration and overall cognitive function in past research.

The problem, though, is that we don’t eat foods or consume nutrients in isolation. The foods, nutrients and phytochemicals in a varied diet are thought to work synergistically to exert health benefits.

In recent years, nutrition research has shifted to examining “dietary patterns” in order to capture the complexity of diet. A dietary pattern is defined as the quality, quantity, variety and combinations of foods eaten on a regular basis.

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One of the best-known dietary patterns is the well-studied Mediterranean diet. In Mediterranean countries, adherence to this way of eating has been associated with a slower rate of cognitive decline and a lower risk of Alzheimer’s disease.

Few studies, however, have explored the link between a Mediterranean diet and cognitive health in non-Mediterranean countries.

Now, two of the largest studies conducted to date, published in the October issue of the American Journal of Clinical Nutrition, provides further evidence that a Mediterranean dietary pattern benefits cognitive health in adults who live outside of the Mediterranean region.

The latest findings

In Britain, researchers evaluated dietary data that were collected from 8,009 healthy older adults of ages 40 to 79, between the years 1993 and 1997. Participants were then followed for 13 to 18 years at which time they underwent a battery of cognitive function tests.

Those whose diets closely matched the Mediterranean diet had significantly better overall cognitive function and performance on cognitive tests than participants who had low Mediterranean diet scores. The researchers accounted for factors that could influence the risk of cognitive impairment, including body mass index, smoking status, physical-activity level and education.

The second study, conducted among 16,948 healthy Chinese adults, examined whether closely adhering to a healthy dietary pattern in mid-life influenced the risk of cognitive impairment later in life. (Mild cognitive impairment may increase the risk of developing Alzheimer's disease.)

Participants’ diets were scored based on how closely they adhered to the Mediterranean diet, the DASH (Dietary Approaches to Stop Hypertension) diet, a plant-based diet and two other healthy eating indices. Diet quality was assessed at ages 45 to 75; cognitive function was evaluated 20 years later.

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Compared with participants whose diets adhered the least to any healthy dietary pattern, those with diets that closely matched one had a significantly lower risk of cognitive impairment later in life. The strongest protective effect was attributed to the Mediterranean diet.

Limitations

Cognitive function was measured once, at the end of each study, so the researchers weren’t able to capture possible cognitive decline over time. Dietary intake was assessed only at the start of each study so it’s not known if participants changed their diets during the follow-up periods.

As well, the results may have been influenced by factors that weren’t accounted for, such as childhood cognition, a variable that‘s related to healthier food choices and, in turn, better cognitive function.

Even so, these two large studies add to increasing evidence that a Mediterranean dietary pattern helps maintain cognitive fitness as we age.

What’s in a Mediterranean diet?

The Mediterranean diet is a plant-forward way of eating that’s characterized by a daily intake of vegetables, fruits, whole grains, beans and lentils and nuts. The principal fat, which is used liberally, is extra virgin olive oil, high in monounsaturated fat.

Fish, chicken, eggs, yogurt and cheese are consumed in moderate amounts, whereas red meat, sweets and pastries, butter and highly processed foods are eaten infrequently. Wine is consumed in small amounts, typically with meals.

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Herbs and spices, rich in anti-inflammatory phytochemicals, are used to flavour foods.

It’s thought that the Mediterranean diet protects the brain by providing nutrients, antioxidants and phytochemicals that reduce inflammation and protect cells from free radical damage. Components of whole grains, fruits and vegetables also influence the brain by supporting a healthy gut microbiome.

It’s the combined effect of the Mediterranean dietary pattern that counts, not its individual foods.

Leslie Beck, a Toronto-based private practice dietitian, is Director of Food and Nutrition at Medcan.

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