The link between cardiovascular disease and eating lots of red meat is relatively well established, but what isn’t so clear is exactly how animal proteins can raise heart disease risk. A new study has homed in on one potential mechanism, illustrating how metabolites produced by certain gut bacteria while digesting red meat play a significant role in cardiovascular disease.
“Several ingredients and mechanisms have been proposed to explain potential harmful effects of meat intake on ASCVD [atherosclerotic cardiovascular disease],” the new research noted. “These include contents of saturated fat, cholesterol, and heme iron in red meats, as well as sodium, nitrites, and high temperature cooking of processed meats. However, true mechanisms are surprisingly poorly understood.”
To fill a gap in the research, this new study focused on several metabolites produced by bacteria in the gut. In particular the investigation looked at levels of trimethylamine-N-Oxide (TMAO), a molecule previously linked to poor cardiovascular health.
When animal proteins containing the chemical L-carnitine are digested by certain types of gut bacteria, a molecule called trimethylamine (TMA) is produced. TMA is subsequently turned into TMAO in the liver and this leads to cardiovascular damage.
The new research looked at data from a long-term cardiovascular study following thousands of subjects for over a decade. The study is the first to try and understand the different ways red meat consumption can heighten heart disease risk.
The findings revealed blood plasma levels of TMAO and two other microbiome-produced metabolites could account for between 8% and 11% of a person’s increased heart disease risk from eating red meat. Increased blood glucose levels and systemic inflammation also were linked with heart disease risk, according to the new findings.
Dariush Mozaffarian, co-senior author on the study, said the interesting part of the findings was that these three factors seemed to be more relevant to raising a person’s heart disease risk than more traditional things such as fat or cholesterol.
“Interestingly, we identified three major pathways that help explain the links between red and processed meat and cardiovascular disease – microbiome-related metabolites like TMAO, blood glucose levels, and general inflammation – and each of these appeared more important than pathways related to blood cholesterol or blood pressure,” explained Mozaffarian. “This suggests that, when choosing animal-source foods, it’s less important to focus on differences in total fat, saturated fat, or cholesterol, and more important to better understand the health effects of other components in these foods, like L-carnitine and heme iron.”
Another recently published study co-authored by Mozaffarian looked at blood levels of TMAO and all-cause mortality. That research found older adults with high levels of TMAO had a 20% to 30% higher risk of death than people with low blood levels of TMAO.
Meng Wang, a co-author on both recent studies, said most research has focused on the risks of red meat in relation to dietary saturated fat and blood cholesterol levels. However, this new study indicates several other pathways by which red meat intake harms cardiovascular health. And these findings can inform new interventions for improving heart health.
“These findings help answer long-standing questions on mechanisms linking meats to risk of cardiovascular diseases,” said Wang. “The interactions between red meat, our gut microbiome, and the bioactive metabolites they generate seem to be an important pathway for risk, which creates a new target for possible interventions to reduce heart disease.”
The study was published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.
Source: Tufts University