How healthy diets like the Mediterranean diet help protect brain health

  • A new study finds that across races and ethnicities, metabolites from healthier diets may help protect brain health.
  • Diet is an important source of many metabolites that can be markers for various aspects of our health.
  • Past research has found that certain metabolites — including lipids, amino acids and steroids — are linked to cognitive decline and dementia.

A new study from researchers at Brigham and Women’s Hospital has further confirmed what is already known about the link between diet and cognitive abilities—that what we eat can affect our brain health.

Metabolites from healthier diets, such as the Mediterranean diet, are associated with stronger cognitive function, while metabolites from diets higher in sugar are associated with poorer cognitive function, according to the report, which was published in Alzheimer’s and dementia OnFriday.

The researchers also showed that these findings could be generalized to different races and ethnicities.

“Research like this shows us that what we eat can have a profound effect on brain function. Diet is much more than your weight; affects how your brain and body function and can have a significant effect on your mental and physical health,” Christopher Palmer, MD, assistant professor of psychiatry at Harvard Medical School and author of Brain energysaid.

The researchers wanted to understand how metabolites—substances produced in the body during digestion—affect cognition.

Different metabolites are produced by different types of foods, and some are associated with positive health outcomes, while other metabolites are consistently associated with worse health outcomes.

“Some metabolites are very healthy and good for us (e.g. B12 helps with neurological function, so we want to make sure we get enough of it if we’re vegan), and some of them are not so good for us (ribitol was example from the study) and may negatively impact our knowledge,” says Dana Ellis Hance, MD, senior clinical nutritionist at UCLA Medical Center, an assistant professor at the UCLA Fielding School of Public Health.

The research team assessed metabolite levels and cognitive function in 2,222 Hispanics and Latinos, 1,365 Europeans, and 478 African Americans.

They then tested whether metabolites previously associated with cognition were in past research can be applied to the three different racial and ethnic groups included in the study.

The research team found that six metabolites—four of which were sugars or sugar derivatives—were associated with poorer cognitive function. Another type of metabolite, beta-cryptoxanthin, which is associated with fruit consumption and the Mediterranean diet, is associated with stronger cognitive function.

The findings can be generalized to all racial and ethnic groups involved.

The researchers believe that metabolites may be biomarkers of the underlying relationship between diet and cognitive function. They did not find a strong casual association between metabolites and cognitive health, but hope that future studies will investigate how metabolites may directly affect cognition.

Paula Doebrich, MPH, RDN, a registered dietitian at Happea Nutrition, says the study should be interpreted with caution because there are some limitations.

“This study simply highlights the importance of following an overall healthy diet for long-term health, but does not provide any specific data on what exactly we can do from a dietary perspective to prevent cognitive decline,” Dobrich said.

Although the study confirms that people who eat poorer diets may be at higher risk of chronic disease, the findings should not be used to make specific dietary recommendations, Dobrich says.

Other potential contributing factors known to influence cognitive health—such as socioeconomic status, physical activity, and social support—were not included in the assessment, and sugar intake was never measured among participants, making it difficult to identify specific dietary recommendations to stimulate brain health.

Diet is an important source of many metabolites that can be markers for various aspects of our health.

“In general, healthy plant-based food tends to have more of the healthy, safe, beneficial metabolites, and less healthy foods (heavily processed) will have more of the less safe, unhealthy metabolites that negatively affect cognition” , says Hunes.

Past research found that certain metabolites—including lipids, amino acids, and steroids—were associated with cognitive decline and dementia. Palmer says that sometimes the body can have trouble processing large amounts of specific metabolites, which can have adverse effects on the body and brain.

It is still unclear whether and how metabolites directly affect cognition, but researchers say there is a clear link between cognition and various metabolites. In addition, metabolites can be a useful biomarker to help scientists better understand brain diseases such as Alzheimer’s disease and dementia.

According to the researchers, the relationship probably goes both ways—diet affects our cognition and our cognition affects our diet.

“This study was correlational, meaning they did not prove that high blood sugars and sugar metabolites directly cause cognitive impairment. In fact, they found some evidence of ‘reverse causation,’ meaning that pre-existing cognitive impairment can influence people’s dietary choices,” says Palmer.

Ultimately, the findings highlight the importance of following a healthy diet that is rich in fruits and vegetables.

“Eat more unprocessed whole foods — like the Mediterranean diet — and less processed foods that are high in sugar or low in vitamins and minerals,” Hunes said.

Doebrich recommends following Dietary Guidelines for Americans. Make sure at least half of your grains are whole grains and replace half of your protein with plant sources, she adds.

“Keep in mind that cognitive health is related to lifestyle habits outside of diet, such as social interactions, hobbies, good sleep hygiene, physical activity, or alcohol and substance abuse, among others,” Dobrich said.

New research confirms that what we eat can affect our brain health. By analyzing the levels of metabolites, or substances produced in the body during metabolism, the researchers found that certain types of food were associated with better or worse cognitive health. Although it is not clear how the metabolites directly affect cognitive function, the findings suggest that there is an underlying link between the two and highlight the importance of eating a diet rich in fruits and vegetables.

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