Could the Mediterranean diet help slow decline?
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- Previous research into how protective the Mediterranean diet is of cognitive health has been inconclusive, partly because many studies have been based on dietary self-reports.
- By tracking metabolites in blood, scientists can gain a more accurate understanding of the foods a person ingests since it does not rely on self-reporting, which is often inaccurate in dietary studies.
- Now, a new prospective study based on an analysis of participants’ metabolome has found more definitive evidence that consuming a Mediterranean diet promotes a slowing of cognitive decline in older people.
A solid connection between a Mediterranean diet and cognitive health has remained somewhat elusive. This is most likely because so many studies rely on participants’ self-reporting of their dietary intake, a notoriously unreliable means of collecting data.
A new study takes a different approach to measuring diet and selecting cases and controls. The study was conducted in two French regions; one was the discovery cohort and the other was used to validate the findings. The researchers used a nested case-control study design in each city to reduce bias between cases and controls.
In both cases, people with cognitive decline after 12 years of follow-up and the controls, those without cognitive decline at follow-up, were selected from the same regional cohort (the “nest”).
The authors overcame inaccuracies in diet recall by using biomarkers in blood samples taken at baseline to measure how much different components of a Mediterranean diet had reached participants’ bloodstreams.
Using blood serum biomarkers rather than participants’ recollections, the new study has found that people eating a Mediterranean diet are less likely to experience age-related cognitive decline.
The authors of the study developed a scoring system that measures individuals’ adherence to the Mediterranean diet. They call their system MDMS, which stands for “Mediterranean Diet Metabolomic Score.”
The researchers analyzed the participants’ blood serum for the presence of metabolites that result from the cellular processing of certain foods, resulting in an MDMS score.
Data from the
None of the individuals had dementia at the outset of the 3C study in 1999–2000 when cognitive tests were administered. The participants were repeatedly tested every two to three years over a period of 12 years to capture any development of dementia.
At the outset of the 3C study, researchers took blood samples from the participants to measure 72 metabolites of interest.
In the new study, individuals from the Bordeaux region whose MDMS test results showed the greatest adherence to the Mediterranean diet were 10% less likely to develop mild cognitive impairment than people with lower test scores. In the Dijon region, they were 9% less likely to do so.
The study is published in the journal
“Metabolites, which are products of various cellular processes, can provide insights into an individual’s physiological state,” said Dr. Menka Gupta, functional medicine doctor at Nutranourish, who was not involved in the study.
“[The] breakdown and metabolism of consumed foods and nutrients generate various metabolites. By measuring food intake biomarkers, researchers can indirectly infer the resulting metabolites in the body. This helps us pinpoint the promise of certain foods in investigating cognitive decline,” Dr. Gupta explained.
Metabolomics — studying a person’s metabolites — provides a greater degree of certainty regarding the foods a study participant is consuming.
Michelle Routhenstein, preventive cardiology dietitian at EntirelyNourished.com, who was also not involved in the study, said “Tracking food consumption in Mediterranean diet studies typically relies on food-frequency questionnaires which may lack accuracy due to subjective memory recall and reporting.”
“This study is one of the first studies to assess the benefits of cognitive health and Mediterranean diet via metabolomic signatures.”
— Michelle Routhenstein
According to Dr. Austin Perlmutter, internal medicine physician and New York Times bestselling author, the metabolites tracked in this study are proxies for key components of the Mediterranean diet. These include “polyphenolics as well as omega-3 fatty acids including DHA and EPA, all of which have been linked to better cognitive health.”
He noted that “a diet rich in polyphenols including, in particular, quercetin and kaempferol has been correlated with slower cognitive decline, while consuming more omega-3 fatty acids is supported as a preventive strategy for Alzheimer’s.”
“One of the plant-based food biomarkers looked at was enterolactone,” said Routhenstein, “which is created as a metabolite of lignan consumption, specifically flax seeds and sesame seeds. Lignans have been shown to be neuroprotective and enhance cognitive memory.”
Routhenstein also pointed out that included in the analysis were monounsaturated fatty acids, “the heart-healthy fat found in the Mediterranean diet.”
“Studies show that oleic acid may have a beneficial effect on cognitive decline by enhancing memory functioning,” she said.
“The link between diet and cognitive decline has been examined in a host of studies, and is of increasing importance as the global population ages,” said Dr. Perlmutter, highlighting that the most significant threat to long-term cognition is Alzheimer’s disease.
“With an expectation of over
Dr. Perlmutter cited research published earlier this year reporting an association between diet and Alzheimer’s disease, saying, “The researchers determined that individuals who reported adhering to either a MIND or Mediterranean dietary pattern exhibited fewer Alzheimer’s disease-related brain markers, even after accounting for reported levels of physical activity and smoking habits.”
The MIND diet is a combination of the Mediterranean and DASH diets.