A Mediterranean-style diet that appears to cut the risk of heart disease also may help protect against Alzheimer's disease, a new study suggests.
People who followed the diet were up to 40 percent less likely than those who largely avoided it to develop Alzheimer's during the course of the research, scientists reported.
Still, more research must be done before the diet can be recommended to ward off Alzheimer's, said Dr. Nikolaos Scarmeas of the Columbia University Medical Center in New York, lead author of the research. The work was recently published online by the Annals of Neurology.
The diet he tested includes eating lots of vegetables, legumes, fruits, cereals and fish, while limiting intake of meat and dairy products, drinking moderate amounts of alcohol and emphasizing monounsaturated fats, such as in olive oil, over saturated fats. Previous research has suggested that such an approach can reduce the risk of heart disease.
Prior research has also suggested that certain components of the Mediterranean diet can reduce the risk of developing Alzheimer's, Scarmeas said. But he said the previous work has tended to focus on individual nutrients like vitamin C or foods like fish. By studying a comprehensive diet instead, the new research could take possible interactions between specific foods and nutrients into account, he said.
The idea that a heart-healthy diet could also help fight Alzheimer's fits in with growing evidence that "the kinds of things we associate with being bad for our heart turn out to be bad for our brain," said Dr. Marilyn Albert, a Johns Hopkins neurology professor and spokeswoman for the Alzheimer's Association. The list includes high cholesterol, high blood pressure, obesity, smoking and uncontrolled diabetes, she said.
So it makes sense that a diet low in saturated fats and cholesterol would reduce the risk of Alzheimer's, said Albert, who was not involved in the new study.
The new work is among the most convincing so far to show an effect of diet on Alzheimer's risk, she said. Such large studies are important, she said, "to add to the body of evidence to help persuade people they really can do something in their daily lives to reduce risk."
Scarmeas and colleagues followed 2,258 elderly residents of northern Manhattan for an average of four years. The participants were asked in detail about their dietary habits and evaluated every 18 months or so for signs of dementia. None showed any dementia at the start of the study, but by the end, 262 had developed Alzheimer's.
To look for an effect of diet, the researchers gave each participant a score of 0 to 9 to nine on a scale that measured how closely they followed the Mediterranean diet. Compared to those showing the lowest adherence, those who scored 4 or 5 showed 15 percent to 25 percent less risk of developing Alzheimer's during the study, while those with higher scores had about 40 percent less risk.