In news that sounds a bit like it came straight from a sci-fi thriller, researchers say that eating too much meat might shrink your brain.
On the flip side, however, eating healthy foods from the so-called Mediterranean diet may help your brain stay in good shape as you get older, the new study suggests. The researchers said that people over 65 who ate more fish, vegetables, fruit, grains and olive oil had a larger brain volume than a similar group who didn't follow a Mediterranean diet.
Read: Mediterranean or low-carb – which is best for the brain?
"It was encouraging to see that the more you adhere to this Mediterranean diet, the more protection you get against brain atrophy shrinkage," said study author Yian Gu, an assistant professor of neuropsychology at Columbia University in New York City.
"For people interested in the diet and lifestyle factors leading to better health, I think this is another study consistent with previous studies that indicate the Mediterranean diet is a healthy diet," she added.
But Gu noted that her study's observational findings cannot prove a definitive cause-and-effect relationship between diet and brain volume. The study was only designed to find an association.
Previous research has linked the Mediterranean diet to a lower risk of Alzheimer's disease, the study said. The diet stresses the consumption of vegetables, legumes (beans, peas and lentils), fruits, cereals, fish and monounsaturated fats such as olive oil, the study authors said.
Read: How diet and physical activity affect brain function
The eating plan also includes a low intake of meat, poultry, saturated fats and dairy products, as well as mild to moderate amounts of alcohol, according to the researchers.
For the study, Gu and her colleagues split 674 adults into two groups based on how closely their diets aligned with the Mediterranean diet. Their average age was 80 years. All participants underwent MRI scans of their brains to measure total brain volume and thickness. They also completed questionnaires about their food choices and eating patterns.
The researchers found that brain volumes of those who didn't follow a Mediterranean diet were smaller than those who did. The difference was minor in overall size equated to about five years of aging, the study authors said.
But, more specifically, the investigators found that eating more fish and less meat was associated with even less brain shrinkage.
Read: Eat Mediterranean, live longer
Gu said scientists don't yet know exactly why the Mediterranean diet seems healthier for the brain. However, other research has established that a higher intake of fish and vegetables and a lower intake of meat are beneficial for brain cell growth, she said.
Dr. Joseph Masdeu, director of the Nantz National Alzheimer Center at Houston Methodist Hospital, praised the research as "an elegant way of looking at this [issue]."
Masdeu, who wasn't involved in the research, said, "I think the take-home message is clear . . . a diet containing less meat and perhaps more fish is good for you. There are negative studies [focusing on] the Mediterranean diet as well, but several confirming a positive effect.
So it's tentative, but it's the strongest preventive approach we have [promoting brain health] together with exercise."
Using the study findings, Gu contended that eating at least 3 to 5 ounces of fish weekly, or no more than 3.5 ounces of meat each day, could protect the brain from shrinkage.
Read: Could a 'Mediterranean' diet extend your life?
She acknowledged that study participants may have inaccurately recalled their food consumption habits in the questionnaires used.
"We asked people to recall their past dietary habits, so that's prone to recall bias," she said.
Dr. Malaz Boustani, a spokesperson for the American Federation for Aging Research, said the new study provided "very good messaging" for the public.
"This is an encouraging study that will really make us work harder to see how we can actually encourage people . . . to change their diet to accommodate the Mediterranean diet," said Boustani, also founding director of the Sandra Eskenazi Centrefor Brain Care Innovation at Indiana University. "It makes it very easy for people to do the right thing."
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Image: Mediterranean diet from iStock