This article originally appeared on Medical News Today
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Past studies show the Mediterranean diet may help protect a person from cognitive decline, Alzheimer’s disease, and other types of dementia.
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A new study says the opposite may be true for African Americans, finding that a long-term Mediterranean diet intervention did not help improve cognitive function.
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Scientists did find that the Mediterranean diet intervention helped study participants better adhere to the diet, resulting in clinically meaningful weight loss.
Over the last few years, the Mediterranean diet has gained in popularity as research continues to find new ways in which it may help a person’s overall health.
For example, past studies have linked the Mediterranean diet to a lower risk for heart disease, type 2 diabetes, metabolic syndrome, obesity, and certain cancers.
Previous research has also found that following the Mediterranean diet may help protect a person from cognitive decline, Alzheimer’s disease, and other types of dementia.
However, a new study recently published in the journal Preventive Medicine Reports suggests the opposite may be true for African Americans, finding that a long-term Mediterranean Diet intervention did not help improve cognitive function.
Scientists did find that the Mediterranean diet intervention helped study participants better adhere to the diet, resulting in clinically meaningful weight loss.
Focusing on the African American population
For this study, researchers recruited 185 participants with an average age of 66 at the start of the study and average body mass index (BMI) of 37.1 kg/m², which is classified as obese. Of the participant pool, 91% identified as non-Hispanic Black or African American and 86% identified as female.
“We saw that the ability of diet to improve cognitive health in older African American adults was extremely understudied even though they may be at higher risk for cognitive diseases such as Alzheimer’s disease,” Andrew McLeod, PhD, a post-doctoral research associate at the Institute for Health Research and Policy at the University of Illinois Chicago, and first author of this study, told Medical News Today.
Study participants were randomly selected to follow an eight-month Mediterranean diet lifestyle intervention with weight loss or without weight loss. This intervention period was followed by a six-month maintenance period.
“We chose the Mediterranean Diet because it had been shown to be associated with better cognition in adults,” McLeod said. “However, the evidence at the time of writing the grant for the study was still limited. We felt we needed more evidence of the benefits of a Mediterranean diet before recommending it on a population level scale.”
Fat loss but no changes in cognition
At the study’s conclusion, researchers found that there was no change in cognition after adhering to the Mediterranean diet, regardless of whether weight loss was achieved or not.
“We think that this means that we should be conducting longer dietary interventions, like the PREDIMED trial, which was five years,” McLeod said. “With a study like that, we are confident we would see a cognitive benefit in our study population.”
Scientists did find that those following the eight-month Mediterranean Diet lifestyle intervention with weight loss had improved adherence to the diet and led to greater weight loss, with an average weight loss of 3.8 kg over 14 months, as well as a reduction in visceral adipose tissue mass.
“We think this is important because it suggests that with even longer follow-up, say a few years, our participants may still be adhering to a Mediterranean diet and would still be at a weight lower than when they started the intervention,” McLeod explained. “This may translate not only to cognitive benefits years later, but also cardiovascular and metabolic benefits, ultimately leading to increased lifespan and healthspan.”
“The next steps are potentially to explore the reasons why some participants were strongly adherent to their intervention group and why some were not,” he continued. “We’re also interested in possibly finding subgroups of participants who did benefit cognitively from the trial. We’ll be looking at psychosocial variables, such as level of social support, to try to figure this out. Stay tuned.”
More dementia studies on African American communities needed
MNT had the opportunity to speak with Rehan Aziz, MD, a geriatric psychiatrist at Jersey Shore University Medical Center in New Jersey, about this study, who commented that he was encouraged to see a well-designed trial focused on older African American adults, a group often left out of dementia prevention research.
“My first reaction was appreciation that the study prioritized cultural representation,” Aziz continued. “At the same time, I wasn’t surprised by the finding that short-term changes in diet and weight didn’t translate into cognitive gains over 14 months — because brain health is a long game. A longer-term study with more significant decreases in body mass index may have yielded different results. Still, the weight loss and improved diet quality were real wins that could lower dementia risk indirectly through better cardiovascular and metabolic health.”
As past studies have shown a correlation between following the Mediterranean diet and improved cognitive function, Aziz explained there are a few likely reasons as this was not the case in this study.
“First, the study only ran for 14 months, and cognitive change is slow and may take years to show up. Second, although participants improved their diet and lost weight, the differences between groups may not have been large or sustained enough to impact the brain. Also, some benefits may rely on deeper metabolic changes — like improved insulin sensitivity — which didn’t shift meaningfully in this group.”
— Rehan Aziz, MD
“I’d like to see longer-term studies, at least three to five years, with even greater support for maintaining diet and lifestyle changes,” Aziz added. “Most importantly, we need more dementia prevention trials that center on African American communities.”
New study offers much to learn
MNT also had the chance to speak with David Cutler, MD, a board certified family medicine physician at Providence Saint John’s Health Center in Santa Monica, CA, about this research.
Cutler said that while this study did not find a significant improvement in cognitive function, there is still much to be learned from it.
“Certain limitations to this recent study don’t preclude the possibility that a Mediterranean diet might also yield cognitive benefits in addition to the demonstrated metabolic benefits,” he explained. “The detailed questionnaires and measurements of cognitive functions are not as familiar to most patients and healthcare practitioners as weight and waist circumference. And the efforts to prove cognitive benefits are likewise more challenging than proving metabolic benefits from a Mediterranean diet.”
“The cognitive impact of these sensible dietary changes may not have been detected due to the relatively short 14 months of study — eight months of dietary intervention followed by six months of follow-up,” Cutler continued. “So, despite the study being titled ‘Long-term outcome…’ cognitive impacts may take far longer than a year to develop.”
“We should not dismiss the overall benefits of a calorie-restricted Mediterranean diet over a traditional high saturated fat, low fruit and vegetable American diet. Perhaps the most important benefit is a reduction in body fat, more so than simply a loss in weight. And while this dietary change may not yield a measurable improvement in cognitive function, the positive health effects should not be ignored.”
— David Cutler, MD
View the original article on Medical News Today