It might seem against all logic, but adding a little olive oil or a handful of nuts to your diet each day may help keep your mind clear, researchers reported on Monday. It's the same diet that's also been shown to reduce deaths from heart attacks and strokes.
The researchers found that people who ate these healthy fats were less likely to show the early signs of dementia than those who stuck to a more traditional diet. And this was done in Spain -- where people are already eating a so-called Mediterranean diet.
The findings come from a large and well-publicized trial that showed the Mediterranean diet rich in fruits, vegetables, olive oil and a little wine can cut the risk of heart attacks and strokes by 30 percent. Martinez and colleagues took a part data on 500 volunteers from their own study center, who were followed for more than six and a half years after starting the diet.
A Mediterranean diet includes lots of salad, fruit, vegetables, nuts, a little fish, a little lean meat, a small amount of cheese and olive oil. Wine is also served at meals. In the main study, 7,400 volunteers got extra counseling, and either a weekly supply of extra-virgin olive oil or mixed nuts -- walnuts, almonds and hazelnuts.
The volunteers, aged 55 to 80, were all at high risk of heart disease because of diabetes, a family history of the disease, high blood pressure, unhealthy cholesterol levels -- or they were overweight or smokers. They were randomly assigned to either add more extra-virgin olive oil to their daily diets, a daily handful of the mixed nuts, or just a standard diet with advice to cut fat.
Such "randomized" studies are considered more powerful, because people don't choose which diet to adopt -- and so other outside factors don't interfere with the results. For instance, people who choose to eat nuts might also dislike meat, or they might like sweets, or they might exercise more or less than people who don't think much about eating nuts.
Six years after starting on the diet, the 500 Navarra volunteers took two standardized tests for dementia and the confused thinking, called cognitive impairment, that often leads to dementia.
The researchers found that 60 volunteers had developed mild cognitive impairment. Eighteen had been told to eat more olive oil, 19 had been on the diet with added mixed nuts and 23 of them had been advised to eat a low-fat diet. And 35 people developed dementia: 12 on the added olive oil diet; six who got nuts and 17 on the low-fat diet.
There are several ways that adding olive oil or nuts to the diet might protect the brain, the researchers said. Olive oil and nuts contain monounsaturated fats, which are better for artery health than the saturated fats found in butter, meat and lard. These foods are also high in fiber and vitamin E, as well as minerals. Walnuts are rich in omega-3 fatty acids.
The diet could reduce damaging inflammation, Martinez says. And some studies have suggested that virgin olive oil -- which is cold-pressed and unrefined -- might fight the beta amyloid "plaques" found clogging the brains of Alzheimer's patients. "A third mechanism may be that an improvement in vascular health leads to better brain blood flow," Martinez said by e-mail.
These nutrients protect against the oxidative damage that can cause heart disease, cancer and Alzheimer's. Various studies have shown little benefit from taking vitamins alone, but this study shows the combination of the factors in a healthful diet does seem to have an effect.
Groups like the Alzheimer's Association have been warning that the U.S. will have to cope with a tsunami of Alzheimer's disease as the population ages, with projections that the number of patients with this untreatable form of dementia will triple in the next 40 years, to 13.8 million in 2050.
"Currently, there is no effective therapy to delay the onset or halt the progression of dementia," the researchers noted.