In the nutrition world, how red and processed meats lead to cardiovascular disease and overall poorer health has long been studied. Saturated fats are often viewed as the prime culprit when it comes to the connection. Now, scientists say it may be the effects of red meat on the gut that drive heart disease more than unhealthy fats.
While it’s important to ultimately have a clear understanding of how these foods are processed in the body and what that means for chronic disease, it is particularly so for elderly people. A new study by Tufts University and Cleveland Clinic researchers assesses the risk of red and processed meat in a large sample of older adults, including close to 4,000 American seniors.
Previously, scientists have studied the relationship between heart disease and saturated fat, dietary cholesterol, sodium, nitrates/ites, and cooking oils on high-heat. The results have remained inconsistent, but recent evidence suggests that the underlying mechanisms may may be explained by the changes in gut bacteria when meat is consumed. This study is the first to investigate the correlation between animal-based foods and risk of atherosclerotic cardiovascular disease (ASCVD) instances, and how this affected by gut microbiota in addition to normal markers like blood sugar, blood pressure, and high cholesterol.
Study authors used data from a study done by the National Institutes of Health (NIH) called the Cardiovascular Health Study. This long-term observational study focuses on specific risk factors in Americans over 65. Many blood biomarkers were measured at the start and again during follow-up. This includes levels of the gut microbiome-made trimethylamine N-oxide (TMAO) and two of its key naturally-occurring molecules, gamma-butyrobetaine and crotonobetaine, which come from L-carnitine, a chemical that’s plentiful in red meat.
In this study, subjects were followed for around 12.5 years, and their average age at the beginning was 73. This was adjusted for additional risk factors like age, sex, race/ethnicity, education, smoking, physical activity, other dietary habits, and more. Results reveal that the gut plays a much more significant role than previously thought in ASCVD risk.
“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,” says co-senior author, Dariush Mozaffarian, dean for policy at Tufts’ School of Nutrition Science and Policy. “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.”
It’s not always the first thought to consider the gut microbiome as means of determining risk or as a reason that someone has cardiovascular disease. In recent years, the long-held belief that saturated fat is the main driver has been changing, and the researchers hope that their work continues to keep this idea moving in the right direction.
While these results were promising in elderly adults, the team agrees that more research should be done to see if the findings can apply to people of younger ages and backgrounds. If findings are similar across other demographics, this could help improve early detection measures and heart healthy dietary recommendations.
This study is published in the journal Atherosclerosis Thrombosis and Vascular Biology.