A diet containing red meat comes with a higher risk of atherosclerosis and consequent cardiovascular disease, this much is well known. Researchers here look through epidemiological data in order to assess which are the more relevant of the mechanisms known to contribute to this relationship between diet and the development of fatty lesions in blood vessel walls. Their analysis suggests cholesterol level is not a relevant link, while mechanisms leading to increased chronic inflammation are important, as is the fact that red meat leads to a gut microbiome that produces significant TMAO, a metabolite that in turn negatively affects cardiovascular health.
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 of 3,931 U.S. men and women over age 65 shows that higher meat consumption is linked to higher risk of atherosclerotic cardiovascular disease (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.
In this community-based cohort of older U.S. men and women, higher intakes of unprocessed red meat, total meat (unprocessed red meat plus processed meat), and total animal source foods were prospectively associated with a higher incidence of ASCVD during a median follow-up of 12.5 years. The positive associations with ASCVD were partly mediated (8-11 percent of excess risk) by plasma levels of TMAO, gamma-butyrobetaine, and crotonobetaine. The higher risk of ASCVD associated with meat intake was also partly mediated by levels of blood glucose and insulin and, for processed meats, by systematic inflammation but not by blood pressure or blood cholesterol levels. Intakes of fish, poultry, and eggs were not significantly associated with ASCVD.
"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. The study also argues for dietary efforts as a means of reducing that risk, since dietary interventions can significantly lower TMAO."