Does eating more meat-especially red meat and processed meat-raise the risk of cardiovascular disease, and if so, why? Despite intense study, the impact of animal source foods on atherosclerotic cardiovascular disease (ASCVD) is vigorously debated, and the mechanisms underlying potential effects of animal proteins remain unclear. Understanding the impacts of meat consumption is particularly important in older adults, because they are the most vulnerable to heart disease yet may benefit from intake of protein to offset age-related loss of muscle mass and strength.
Over the years, scientists have investigated the relationship between heart disease and saturated fat, dietary cholesterol, sodium, nitrites, and even high-temperature cooking, but evidence supporting many of these mechanisms has not been robust. Recent evidence suggests that the underlying culprits may include specialized metabolites created by our gut bacteria when we eat meat.
A new study led by researchers at the Friedman School of Nutrition Science and Policy at Tufts University and Cleveland Clinic Lerner Research Institute quantifies the risk of ASCVD associated with meat intake and identifies underlying biologic pathways that may help explain this risk. The study of almost 4,000 U.S. men and women over age 65 shows that higher meat consumption is linked to higher risk of ASCVD-22 percent higher risk for about every 1.1 serving per day-and that about 10 percent of this elevated risk is explained by increased levels of three metabolites produced by gut bacteria from nutrients abundant in meat. Higher risk and interlinkages with gut bacterial metabolites were found for red meat but not poultry, eggs, or fish.
The study, published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB) on August 1, is the first to investigate the interrelationships between animal source foods and risk of ASCVD events, and the mediation of this risk by gut microbiota-generated compounds as well as by traditional ASCVD risk pathways such as blood cholesterol, blood pressure, and blood sugar.
The research drew on years of data from the National Institutes of Health’s (NIH’s) Cardiovascular Health Study (CHS), a long-term observational study of risk factors for cardiovascular disease in Americans age 65 and older. Several blood biomarkers were measured at baseline and again during follow-up, including levels of the gut-microbiome generated trimethylamine N-oxide (TMAO) and two of its key intermediates, gamma-butyrobetaine and crotonobetaine, derived from L-carnitine, abundant in red meat.
