- Studies show that the levels of certain blood metabolites, which are the intermediate or final products of human metabolism, are associated with cognitive function.
- Metabolite levels in the blood are influenced by health status, genetics, and environmental factors, and may differ among different racial or ethnic groups.
- A recent study characterized blood metabolites that were associated with cognitive function among various racial/ethnic groups.
- The study findings suggest that dietary habits could potentially influence the levels of these metabolites and subsequently cognitive performance, highlighting the importance of a healthy diet.
Individuals from racial or ethnic minority groups are often underrepresented in research, making it difficult to understand risk factors and the effectiveness of treatments for diseases in these minority groups.
A recent study published in the journal Alzheimer’s and dementia found that plasma levels of six metabolites were associated with lower cognitive function in all racial/ethnic groups, and blood levels of most of these metabolites were associated with adherence to a Mediterranean diet.
speaking to Today’s medical newsthe corresponding author of the study Dr. Tamar Soferprofessor at Brigham and Women’s Hospital at Harvard University, said:
“We identified some metabolites (small molecules) in the blood whose levels are correlated with cognitive function, and all of them are related to diet. While there are clinical trials showing that diet can influence cognitive function, identifying specific metabolites can help identify [a] specific mechanism, specific components of [a] diet that are more important than others, and biomarkers to measure [the] success of dietary changes.
However, Dr. Sofer added that “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.”
Technological advances have made it possible to profile hundreds of metabolites at a time and identify metabolites associated with a disease state. For example, studies have shown that plasma metabolite levels are associated with cognitive function Y dementia.
Characterizing metabolites associated with cognitive function can help researchers understand the mechanisms underlying the development of dementia. Furthermore, blood metabolites can be easily measured and could serve as biomarkers for cognitive function.
A previous study involving older Puerto Ricans enrolled 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 factorsthat may 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 BPRHS results could be replicated in a different sample of individuals of Puerto Rican descent in the United States. The researchers also investigated whether these findings could be generalized to the broader Hispanic/Latino population and other ethnic groups.
Several metabolites identified by the BPRHS have been shown to be influenced by dietary habits. Therefore, modifying dietary habits could potentially help preserve cognitive health.
Therefore, the study authors also examined the causal role of blood metabolites and dietary habits influencing cognitive function.
To assess the generalizability of the BPRHS results to the broader US Hispanic/Latino population, the researchers used data from 2,222 adults enrolled in the Community Health Study/Study of Latinos (HCHS/SOL). HCHS/SOL is a longitudinal cohort study examining the health of people of different Hispanic/Latino origins, 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 level of 11 of the 13 metabolites evaluated 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 BPRHS.
In addition, there was a significant correlation between the levels of certain metabolites with global cognitive function in Puerto Ricans from HCHS/SOL and all HCHS/SOL participants.
Among 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 enrolled in the Atherosclerosis Risk in Communities (ARIC) to study. The researchers then conducted 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 across all racial/ethnic groups. Four of the six metabolites associated with general cognitive function were sugars, including glucose, ribitol, mannose, and mannitol/sorbitol.
Since the previous analysis only showed a correlation between the metabolites and cognitive function, the researchers performed additional analysis to determine if 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 evaluated the association between dietary habits, including adherence to a Mediterranean diet and food group intake (ie, intake of legumes, fruits, vegetables, meat, fish, etc.), and levels of blood metabolites.
They found that following a Mediterranean diet or its component food groups correlated with several blood metabolites evaluated in the study.
Of note, the strongest association was seen between beta-cryptoxanthin and fruit consumption in Puerto Ricans from HCHS/SOL and in 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 intake of specific 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 eating habits.
In summary, these results suggest that dietary habits could potentially 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 to assess cognitive function, and the causal effects of metabolites on cognitive function should be interpreted with caution.
Dr Perminder Sachdevprofessor of neuropsychiatry at the University of New South Wales, who was not involved in this study, said MNT:
“There are several challenges in interpreting these results in relation to the role of specific nutritional groups and brain health. This is a cross-sectional study from which no causal relationships can be drawn. not only can nutrition affect brain health, but poor cognitive function may also influence nutrition, suggesting a bidirectional relationship.”
Furthermore, Dr. Sachdev also noted that “blood metabolites have multiple determinants, diet being only one of them. Genetic factors, health comorbidities and lifestyle are important. Therefore, a direct attribution to diet is difficult.”
“[T]Their study is a step in the right direction with regard to examining the role of diet and the body’s metabolism for brain health. He provides suggestive evidence that adherence to a good diet, such as the Mediterranean-style diet, may be beneficial for brain health across a wide age range.”
— Dr. Perminder Sachdev
Dr. Sachdev added that much more work was needed.
“We need to better understand the plasma metabolome to know what determines its 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.
