Mediterranean Diet Metabolites May Help Prevent Cognitive Decline

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Metabolites from healthier foods may help protect brain health, according to new research. Ivan Gener/Stocksy
  • Studies show that levels of certain blood metabolites, which are the intermediate or end products of human metabolism, are associated with cognitive function.
  • Blood metabolite levels are influenced by health status, genetics, and environmental factors and can differ between different ethnic or racial groups.
  • A recent study characterized blood metabolites associated with cognitive functions in different ethnic/racial groups.
  • The study’s findings suggest that dietary habits may be able to influence levels of these metabolites and subsequently cognitive performance, highlighting the importance of a healthy diet.

Individuals from disadvantaged ethnic or racial groups are often underrepresented in research, hindering the understanding of risk factors and the efficacy of treatments for disease in these minority groups.

A recent study published in the journal Alzheimer’s & Dementia found that levels of six plasma metabolites were associated with lower cognitive function in all racial/ethnic groups, and levels of most of these blood metabolites were associated with following a Mediterranean diet.

Speak with Medical news todaythe study’s corresponding author, Dr. Tamar Sofer, a professor at Harvard University’s Brigham and Women’s Hospital, said:

“We have identified a few metabolites (small molecules) in the blood whose levels are correlated with cognitive function, and they are all related to diet. While there are clinical studies showing that diet can affect cognitive function, it can identify of specific metabolites help identify [a] specific mechanism, specific components of [a] diet that is more important than others, and biomarkers to measure [the] success of dietary changes.”

dr. However, Sofer added: “There is still work to be done to make these steps happen, but this is a good start, especially as the results held up in a few different studies, so the findings are very reliable.”

Advances in technology have made it possible to simultaneously profile hundreds of metabolites and identify metabolites associated with a diseased state. For example, studies have shown that levels of plasma metabolites are associated with cognitive function and Dementia.

Characterizing metabolites associated with cognitive function could help researchers to understand the mechanisms underlying the development of dementia. In addition, blood metabolites can be easily measured and can serve as biomarkers of cognitive function.

A previous study with older Puerto Rican individuals who participated in the Boston Puerto Rican Health Study (BPRHS) showed that the levels of 13 blood metabolites were associated with global cognitive function, which is a composite measure of multiple cognitive abilities.

Metabolite levels are influenced by the interplay between genetics, health status and environmental factors, including diet, other lifestyle factors and socioeconomic factors, which can differ between and even within ethnic/racial groups.

Given the influence of such a multitude of factors on blood metabolite levels, the study authors examined whether the results of the BPRHS could be replicated in another sample of individuals of Puerto Rican descent in the United States. The researchers also examined whether these findings could be generalized to the wider Hispanic/Latino population and other ethnic groups.

Several metabolites identified by the BPRHS have been shown to be influenced by dietary habits. Thus, adjusting one’s dietary habits may help maintain cognitive health.

Therefore, the study authors also examined the causal role of the blood metabolites and dietary habits in influencing cognitive function.

To assess the generalizability of the results from the BPRHS to the broader Hispanic/Latino population in the US, the researchers used data from 2,222 adults who participated in the Community Health Study/Study of Latinos (HCHS/SOL). HCHS/SOL is a longitudinal cohort study of the health of individuals of diverse Hispanic/Latin backgrounds, including those of Cuban, Dominican, Puerto Rican, Mexican, Central American, and South American descent.

Using blood samples from the HCHS/SOL cohort, the researchers were able to estimate the levels of 11 of the 13 metabolites assessed by the BPRHS.

They found that the direction of the effects of blood metabolites on cognitive function in Puerto Rican HCHS/SOL and all HCHS/SOL participants was similar to that observed in the BPRHS.

In addition, there was a significant correlation between the levels of certain metabolites with global cognitive function in HCHS/SOL Puerto Ricans and all HCHS/SOL participants.

Of these metabolites, higher levels of beta-cryptoxanthin and lower levels of gamma-CEHC-glucuronide were associated with cognitive function in both HCHS/SOL Puerto Ricans and all HCHS/SOL participants.

To examine the association between blood metabolites and cognitive function in other racial/ethnic groups, the researchers used data from 1,365 European Americans and 478 African Americans who participated in the Community Atherosclerosis Risk (ARIC) study. The researchers then performed a meta-analysis to assess the association between blood metabolite levels and cognitive function using data from the BPRHS, HCHS/SOL and ARIC studies.

The meta-analysis showed that six blood metabolites were associated with lower cognitive function in all ethnic/racial groups. Four of the six metabolites associated with overall cognitive function were sugars, including glucose, ribitol, mannose, and mannitol/sorbitol.

Because the previous analysis only showed a correlation between metabolites and cognitive function, the researchers conducted additional analyzes to determine whether any of the blood metabolites had a causal effect on cognitive function.

Of the six metabolites, the analysis revealed a possible causal effect of ribitol alone on cognitive function.

The researchers also assessed the association between dietary habits, including following a Mediterranean diet and food group intake (ie, intake of legumes, fruits, vegetables, meat, fish, etc.), and blood metabolite levels.

They found that following a Mediterranean diet or its constituent food groups was correlated with several blood metabolites assessed in the study.

Notably, the strongest association between beta-cryptoxanthin and fruit intake was observed in HCHS/SOL Puerto Ricans and all HCHS/SOL participants.

Beta-cryptoxanthin is a carotenoid with antioxidant properties found in fruits and vegetables, and beta-cryptoxanthin levels are associated with a lower risk of insulin resistance and liver dysfunction.

The researchers then examined whether the intake of certain food groups had a causal effect on cognitive performance.

Although food groups played a causal role in cognitive performance, cognitive function had a much stronger causal effect on the intake of specific food groups. Cognitive function is associated with socioeconomic status, which may mediate the effects of cognitive status on dietary habits.

Taken together, these results suggest that dietary habits may have the potential to influence cognitive performance by modulating blood metabolite levels.

The authors acknowledge that the study had some limitations. They noted that the BRPHS, HCHS/SOL, and ARIC studies used different methods for assessing cognitive function, and that the causal effects of metabolites on cognitive function should be interpreted with caution.

dr. Perminder Sachdev, professor of neuropsychiatry at the University of New South Wales, who was not involved in this study, told MNT:

“There are several challenges in interpreting these results in relation to the role of specific food groups and brain health. This is a cross-sectional study from which causal relationships cannot be drawn. but poor cognitive function may also affect diet, suggesting a bidirectional relationship.”

In addition, Dr. Sachdev also notes that “blood metabolites have multiple determinants, of which diet is only one. Genetic factors, health co-morbidities, and lifestyle are all important. A direct attribution to food is therefore difficult.”

“[T]his study is a step in the right direction in exploring the role of diet and the body’s metabolism in brain health. It provides suggestive evidence that following a proper diet, such as the Mediterranean diet, can be beneficial for brain health across a wide age range.
—Dr. Perminder Sachdev

dr. Sachdev added that a lot more work was needed.

“We need to better understand the plasma metabolome to know what determines their blood levels before we can begin to interpret such studies. We need longitudinal studies with multiple measurements in large samples, followed by intervention studies, so that a causal relationship can be established,” he said.

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