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Mediterranean diet: Good for your mind and your heart

Plant-based compounds known as polyphenols are plentiful in the Mediterranean diet, which may explain its health benefits.
Image: Thinkstock

Extra-virgin olive oil and nuts seem to contribute to the benefits.

Looking for a diet that may protect your heart and blood vessels? The Mediterranean diet is hard to beat. Over the past several years, findings from a landmark clinical trial in Spain have suggested that this plant-based diet—enhanced with extra-virgin olive oil or nuts—lowers the risk of a heart attack, stroke, and death from heart disease. It even appears to lower the odds of atrial fibrillation (a heart rhythm disorder) and peripheral artery disease (a condition in which fatty plaque clogs arteries throughout the body). Now, new data suggest that the diet is also good for your mind.

“It makes sense, because the brain is an oxygen-hungry organ. You need healthy blood vessels for a healthy brain,” says Dr. Olivia Okereke, assistant professor of psychiatry at Harvard Medical School, whose research explores lifestyle factors that contribute to late-life cognitive decline. Researchers have long appreciated that habits that help the heart also benefit the brain. But the new study is the first clinical trial ever to show possible cognitive gains from one eating pattern over another.

What is PREDIMED?

The Mediterranean diet focuses mainly on fruits, vegetables, whole grains, beans and other legumes, nuts, seeds, and olive oil. It also features moderate amounts of seafood, poultry, eggs, and dairy, but includes only scant helpings of red meat and sweets. In 2003, Spanish researchers launched a major trial of the diet, known as PREDIMED, short for Prevención con Dieta Mediterránea (which means “prevention with Mediterranean diet”). It included 7,500 people, mostly in their 60s and 70s, all of whom were at increased risk for developing heart disease. Most were overweight, and many had high blood pressure or high cholesterol. They were divided into three groups. One followed a Mediterranean-type diet and also ate an extra ounce of mixed nuts (walnuts, hazelnuts, and almonds) a day. Another followed a Mediterranean-type diet and also ate an extra five tablespoons of extra-virgin olive oil a day. The third group, which served as the control, was instructed to follow a low-fat diet.

Thinking and memory improvements

The most recent report from the trial, published May 11, 2015, in JAMA Internal Medicine, included a small subset (447 people) of the PREDIMED participants. They each took six different tests of cognitive function—a combination of memory and thinking skills—at the start of the trial. Three-quarters of them completed the same tests again about four years later.

In the control group, average scores on both types of tests—memory and thinking skills—fell during those four years. By comparison, average scores on the memory tests improved among those following the Mediterranean-type diet with extra servings of nuts, while scores on the tests of thinking skills improved among those following the Mediterranean diet with extra servings of olive oil.

Why Mediterranean matters

The Mediterranean diet is rich in healthy fats, including monounsaturated fat in olives and polyunsaturated fats (including omega-3 fatty acids) in nuts. It also features many foods with plant-based compounds called polyphenols. Together, these substances help quell oxidation and inflammation, which harm blood vessels and the brain. This may explain why the Mediterranean diet seems to prevent both heart disease and age-related cognitive problems, says Dr. Okereke. Not all olive oils are created equal. The new findings are consistent with earlier studies showing that people who closely follow a Mediterranean diet are more likely to maintain their memory and thinking skills over time. Still, it’s worth keeping a few caveats in mind. This study included only 6% of all the PREDIMED participants, and a quarter of them never took the second round of tests. Also, the trial wasn’t designed to look at brain health. So while the findings warrant further study, there’s no downside to eating olive oil, nuts, or a full Mediterranean diet. 

Extra-virgin olive oil: Choose carefully

Extra-virgin olive oil (or EVOO, as it’s sometimes called) is processed without high heat or chemical solvents. This protects the chemicals known as polyphenols thought to be responsible for EVOO’s health benefits. Other grades of olive oil, sometimes labeled “pure” or “light,” go through an additional refining
process that destroys the phenols.

But checking for the term “extra virgin” may not be enough. One study found that two-thirds of imported olive oils labeled as extra virgin failed federal quality standards and were often stale or tasted rancid. And additional testing couldn’t rule out whether the oils were adulterated with refined olive oil. Better-quality oils list a harvest date, so if possible, choose one from a recent harvest (autumn for olives grown in the Northern Hemisphere and spring for those grown in the Southern Hemisphere). Containers that block light are best, since light degrades the oil.

Posted by: Dr.Health

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