Gut Microbes May Increase Risk of Cardiovascular Disease From Meat

Cardiovascular disease is the leading cause of death in the United States and worldwide. Although age is a main risk factor, lifestyle can play a huge influence—healthy foods, good sleep, healthy body weight, and controlling high blood pressure and cholesterol may help reduce risk.

Gut microbes that digest red meat may produce chemicals that can increase the risk of cardiovascular disease, according to a new study in the journal Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB).

“Most of the focus on red meat intake and health has been around dietary saturated fat and blood cholesterol levels,” said Meng Wang, PhD, a postdoctoral fellow at Tufts University in Boston, and co-lead author, in a press release.

Metabolites are chemical products from food digestion. TMAO (trimethylamine N-oxide) is specifically produced by the gut to digest red meat. TMAO and other metabolites have been linked to an increased risk of cardiovascular disease in past research, according to the authors of the current study. High TMAO in the blood can also be linked to chronic kidney disease and type 2 diabetes.

For this study, researchers looked particularly at the relationship between TMAO and L-carnitine (a chemical in meat) on the risk of cardiovascular disease and red meat on individuals 65 years of age and older.

Researchers for the Cardiovascular Health Study (CHS) recruited 5888 participants from 4 communities across the states, starting recruitment in 1989-1990. The participants who enrolled did not have clinical cardiovascular disease—and on average they were 73 years of age, were 88% white, and two-thirds were female.

Patients followed-up with researchers after 12.5 years (median), at which point they were assessed on medical history, lifestyle, health conditions, and sociodemographic characteristics such as education, age, and household income.

Researchers conducted a study measuring levels of metabolites in blood samples, including TMAO, gamma-butyrobetaine, and crotonobetaine, at the beginning of the study and again in 1996-1997. Researchers also looked at the risk of red meat on cardiovascular risk from blood sugar, inflammation, blood pressure and blood cholesterol. The participants answered two questionnaires about dietary habits as well, once at the beginning of the study, and again in 1995-1996.

Investigators then analyzed the risk of different types of animal-based foods—red meat, processed meat, fish, chicken, and eggs. More red and processed meat increased the risk of atherosclerotic cardiovascular disease by 22% at 1.1 serving/day.

One-tenth of this 22% risk came from TMAO and related metabolites in blood. However, blood sugar and inflammation seem to link red meat to increased risk of cardiovascular disease more than blood cholesterol or blood pressure.

“Research efforts are needed to better understand the potential health effects of L-carnitine and other substances in red meat such as heme iron, which has been associated with type 2 diabetes, rather than just focusing on saturated fat,” Wang said.

The study was limited in its observational nature. Researchers cannot prove that gut microbe-generated chemicals from eating meat increases the risk of cardiovascular disease. There could also be errors in participants’ self-reporting, and it was not a diverse study group, therefore the results may not apply to other ages and races.

Reference

Increased heart disease risk from red meat may stem from gut microbe response to digestion. EurekAlert! Aug 1, 2022. Accessed Aug 1, 2022. https://www.eurekalert.org/news-releases/960010