Study Casts Doubt on Mediterranean Diet's Benefit to Brain

THURSDAY, Oct. 13, 2022 (HealthDay News) -- A healthy diet might not protect you from dementia as some have suggested, according to a new Swedish study.

The Mediterranean diet — which includes lots of vegetables, fruits, fish and healthy fats and little dairy or meat — has been touted as brain-protective. But Swedish researchers now say it appears not to be. Others, however, say these new results need to be taken with a grain of salt.

Heather Snyder, vice president of medical and scientific relations at the Alzheimer's Association, isn't convinced that the findings published online Oct. 12 in the journal Neurology are conclusive.

"It is critically important to better understand the links between diet and nutrition and dementia risk," Snyder said.

These new results should be considered in the bigger context of the ongoing work, said Snyder who had no part in the study.

"This is an observational study that can find an association between factors but does not prove causation," she said. "For that, we need an intervention study; fortunately, there are studies today that are testing dietary and nutrition-related interventions."

Snyder said existing data suggest that strategies to reduce dementia risk should be considered in combination, not one at a time. As such, the Alzheimer’s Association is leading the U.S. POINTER Study, a two-year clinical trial to evaluate whether lifestyle interventions that simultaneously target multiple risk factors can protect mental function in older, at-risk adults.

"The connections between diet and dementia risk must be examined in multiple studies across multiple populations and even multiple countries — which, as a result, may yield different results," she noted.

For the new study, a team at Lund University led by Dr. Isabelle Glans collected data on 28,000 Swedes without dementia (average age: 58). Over 20 years, 7% developed dementia, including Alzheimer's disease.

When researchers examined participants' diets, they found no difference in dementia risk between those who ate a conventional or Mediterranean diet.

"While our study does not rule out a possible association between diet and dementia, we did not find a link in our study, which had a long follow-up period, included younger participants than some other studies and did not require people to remember what foods they had eaten regularly years before," Glans said in a prepared statement.

Samantha Heller, a senior clinical nutritionist at NYU Langone Health in New York City, added that evidence for the effects of diet on the risk of various dementias is conflicting.

"Contrary to the conclusions of this large study, there are studies that have found a decreased risk for dementias and cognitive decline with adherence to the Mediterranean diet," said Heller, who reviewed the findings. "It is important to look at the bigger picture, which is the overall effect of dietary patterns on disease risk and quality of life."

She said there is much evidence to suggest that a healthy eating pattern significantly reduces the risk of or helps manage several chronic, often preventable, diseases. Among them: heart disease, type 2 diabetes, stroke, high blood pressure, certain cancers, kidney disease and cognitive (mental) decline, Heller said.

She pointed to such eating patterns as MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay); DASH (Dietary Approaches to Stop Hypertension); Mediterranean; or other plant-based regimens.

"Eating a variety of whole grains, legumes, vegetables, fruits, nuts and other high-fiber foods helps ensure our bodies and brains are getting the nutrients they need to stay healthy and fight disease," Heller said. "Keeping physically and mentally active and getting enough sleep also helps improve brain health."

The study and an accompanying editorial were published online Oct. 12 in the journal Neurology.

Dr. Nils Peters of University Hospital Basel in Switzerland co-wrote the editorial.

"Diet as a singular factor may not have a strong enough effect on cognition, but is more likely to be considered as one factor embedded with various others, the sum of which may influence the course of cognitive function," he wrote, citing diet, regular exercise, controlling heart risk factors, avoiding tobacco and drinking in moderation as among them.

More information

The U.S. National Institute on Aging has more about diet and dementia.

SOURCES: Heather Snyder, PhD, vice president, medical and scientific relations, Alzheimer's Association, Chicago; Samantha Heller, MS, RD, CDN, senior clinical nutritionist, NYU Langone Health, New York City; Neurology, Oct. 12, 2022, online