Brain Boost: Mediterranean Diet May Fend Off Memory Loss

May 12, 2015
Originally published on May 19, 2015 6:44 pm

If you've ever walked out of the house without your phone and wallet — as I did yesterday — you might have wondered: Am I starting to lose it?

Even if you're too young for any real concern about dementia, this kind of precursor to a "senior moment" can be rattling.

But a new study suggests we're not powerless when it comes to keeping our mental acuity and memory intact.

Researchers have documented that a Mediterranean diet rich in vegetables, fish, whole grains, along with daily servings of nuts and olive oil can help fend off age-related cognitive decline.

The study, which appears in JAMA Internal Medicine, compared the brain health of groups of older people in Spain (in their 60s and 70s) who were enrolled in a randomized clinical trial.

One group was assigned to eat a Mediterranean diet, plus either extra daily servings of extra-virgin olive oil (about four tablespoons) or daily servings of nuts. Another group was assigned to eat a lower-fat diet.

During the study, researchers gave the men and women a battery of cognitive tests to gauge various aspects of brain health, from working memory to processing speed to executive function. After about four years, the tests were repeated a second time.

"What we see here is that the control diet group [the people eating the lower-fat diet] worsened on their cognitive tests," Emilio Ros, a researcher at the Hospital Clinic of Barcelona and the lead author of the study, says.

By comparison, the people following the nut-and-oil-rich Mediterranean diet held steady on their cognitive test scores. In other words, their memories did not get significantly better, but there was no measurable age-related decline either.

"The key finding here is that this [Mediterranean] diet is preventing decline," says Dariush Mozaffarian, dean of the Friedman School of Nutrition Science and Policy at Tufts University.

"I think it's encouraging news," says JoAnn Manson, chief of the division of preventive medicine at Brigham and Women's Hospital and a professor of medicine at Harvard University. She says the study suggests that there can be benefits to making diet changes, "even among people in their 60s, 70s or older."

This study is a follow-up to an original finding from the PREDIMED study, a long-term nutritional intervention study of the effectiveness of the Mediterranean diet in seven communities in Spain. As we've reported, the researchers documented in 2013 that the Mediterranean diet cut the risk of heart attacks and strokes by about 30 percent.

When you put the two findings together, they build on the evidence that eating a heart-healthy diet can also protect the brain.

"There's increasing evidence that what's good for the heart is also good for the brain. The two are strongly interconnected," Manson says. The Mediterranean pattern of eating is also linked to improvements in cholesterol levels, blood pressure and blood glucose regulation, Manson adds. So, it makes sense that the heart and the brain may benefit.

There are still questions about how exactly the Mediterranean pattern of eating might be conferring such benefits.

As we age, our cells may be damaged by free radicals — a process called oxidative stress. But as Ros and his co-authors write in the paper, it is possible to counteract free radicals by eating antioxidant-rich foods. And by countering oxidative stress, we might also get "protection from neurodegenerative disorders."

Certainly a whole range of foods in common in the Mediterranean diet — from fruits and vegetables to fish and nuts — are rich in antioxidants. Some research points to specific compounds in olive oil, such as oleocanthal, as beneficial, too, because they may limit inflammation.

It's also possible that part of the cognitive effect may not be directly related to diet. "It could be that the people on the Mediterranean diet are also changing some other aspect of their lives," says Murali Doraiswamy, a brain scientist at Duke University. Perhaps they're walking more or smoking less.

Doraiswamy says the study is encouraging, but he doesn't find it conclusive. He points out that the study didn't go on long enough to track rates of dementia. So, he says, it's not known whether the staving off of memory loss translates into a reduced rate of Alzheimer's down the road.

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When it comes to eating well and heart health, a lot of research points to the benefits of a Mediterranean-style diet. And another study now adds to that evidence, showing this pattern of eating may give our brains a boost, too. NPR's Allison Aubrey reports what we put on our plate may help stave off cognitive decline.

ALLISON AUBREY, BYLINE: If you happen to be one of the millions of people pushing through middle-age with a few bad eating habits and a less-than-ideal dress size or pant size, you might be encouraged by this new study. About a decade ago, researchers in Spain recruited men and women in their 50s, 60s and 70s, all of whom were overweight and had other risk factors for heart disease, too, such as high blood pressure. And they asked these people to go on a diet.

Some were put on a Mediterranean-style diet, rich in vegetables, fish, whole grains, as well as extra servings of either olive oil or nuts. Another group was put on a lower fat diet. And what the researchers found is that the people who followed the oil and nut-rich Mediterranean diet cut their risk of heart attacks and strokes by about 30 percent. Dariush Mozaffarian, who's dean of the nutrition school at Tufts University, says the finding was striking.

DARIUSH MOZAFFARIAN: That finding rocked the science world by showing in a trial that a diet rich in healthy fats can reduce heart attacks and strokes.

AUBREY: That was published two years ago, and now, this week, researchers tell us what they've learned about what's happening in the brains of the people in this Mediterranean diet study. It turns out, early in the study they gave many of the men and women a bunch of memory and cognition tests.

MURALI DORAISWAMY: These were cognitively normal people, so essentially, these people were all performing normally.

AUBREY: That's Murali Doraiswamy, a brain health scientist at Duke University. He was not involved in the study, but he agreed to look at the results with us. He explains when the researchers did another round of memory tests four years later, they found that the people following the Mediterranean diet, supplemented with all the good fats and olive oil and nuts, showed no memory loss and were more mentally sharp compared to people following the lower-fat diet. Doraiswamy says the results are encouraging.

DORAISWAMY: I think the brain is changing throughout life, and I think what this study shows is that even in your 60s, diet can influence your brain in a beneficial way.

AUBREY: Doraiswamy says there are still lots of questions about how exactly healthy fats and the Mediterranean pattern of eating might confer such benefits. The leading theory is that the diet helps reduce inflammation and oxidative stress. Harvard University's JoAnn Manson says the diet is likely acting in many different ways. And she says the big picture here is that the study adds to the evidence that eating a heart-healthy diet also protects our brains.

JOANN MANSON: There's been increasing evidence that what's good for the heart is also good for the brain. The two are strongly interconnected.

AUBREY: And so, Manson says, the new findings are encouraging. They show, changing your diet, even later in life, can be beneficial. Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.