What is already known on this topic
Trimethylamine N-oxide (TMAO) is a microbial metabolite generated from dietary choline, betaine, and carnitine, which are found in foods such as red meat. High levels of TMAO have been associated with increased risk of cardiovascular events, including the narrowing of arteries and heart attack, as well as poor cardiometabolic health. Gut microbes have been linked to the production of TMAO, but the specific microbial species have not yet been identified.
What this research adds
Researchers analyzed dietary habits as well as fecal and blood samples from more than 300 healthy men. The abundance of 10 bacterial species was associated with TMAO levels in the blood. However, high habitual intake of red meat and choline was linked to elevated TMAO levels only in people who had microbial TMAO-producers, such as Alistipes shahii, in their guts.
Conclusions
The study identified microbial taxa that might affect a person’s health. The findings also highlight the interplay between diet and gut microbes in producing metabolites that may influence cardiometabolic health.
Habitual consumption of red meat can increase the blood levels of trimethylamine N-oxide (TMAO), a metabolite associated with cardiovascular diseases. New research suggests that a person’s gut microbiota can determine whether high habitual red meat consumption results in elevated TMAO levels.
The study, published in the journal Gut, identified microbial taxa that might affect a person’s health. The findings also highlight the interplay between diet and gut microbes in producing metabolites that may influence cardiometabolic health.
Increased risk of cardiovascular events, including the narrowing of arteries and heart attack, as well as poor cardiometabolic health have been associated with high levels of TMAO. TMAO is a microbial metabolite generated from dietary choline, betaine, and carnitine, which are found in foods such as red meat. Gut microbes have been linked to the production of TMAO, but the specific microbial species have not yet been identified.
To address this question, Qi Sun at Harvard University TH Chan School of Public Health and his colleagues analyzed dietary habits as well as fecal and blood samples from 307 healthy men.
Microbial species
The researchers collected up to two pairs of fecal samples and two blood samples, six months apart, from the study participants. They also assessed the participants’ dietary habits using questionnaires and diet records. Then, the team assessed the levels of TMAO in blood samples and analyzed the genetic material present in fecal samples to identify specific microbial species.
All study participants reported to eat regularly a variety of animal and plant foods. Men with higher TMAO levels tended to be older and less physically active than those with lower TMAO levels. They were also more likely to consume more dietary choline and have higher blood levels of choline and carnitine.
The researchers identified 10 species whose abundance was linked to blood levels of TMAO, including 8 Firmicutes species, one Bacteroidetes species and one Actinobacteria species. Microbial species such as Alistipes shahii, Eubacterium biforme and Roseburia hominis have not been linked to TMAO before.
Modifying associations
Consumption of red meat did not seem to be associated with TMAO levels, the researchers found. Instead, high habitual intake of red meat and choline was linked to elevated TMAO levels only in people who had microbial TMAO-producers, such as A. shahii, in their guts.
Habitual consumption of fish was associated with elevated TMAO levels, regardless of whether participants had microbial TMAO-producers in their guts. “In contrast to red meat, fish naturally contains TMA/TMAO, and its intake could increase TMAO levels rapidly without microbial metabolism of choline/L-carnitine,” the researchers say.
The findings suggest that specific microbial TMAO-producers can modify the associations between dietary intake of choline and a person’s blood levels of TMAO. “Identifying functional gut microbiome responses to dietary interventions has the potential to facilitate the development of individualized strategies for more efficient prevention of cardiometabolic diseases,” the researchers say.
