Why does the risk of heart disease increase after eating red meat?
“Most of the focus on red meat intake and health revolves around fat,” said study co-author Meng Wang, Ph.D., a postdoctoral fellow at the Friedman School of Nutritional Sciences. saturation in the diet and blood cholesterol levels. Policy at Tufts University in Boston. “Based on our findings, new interventions could be useful to target interactions between red meat and the gut microbiome to help us figure out how to reduce cardiovascular risk.”
How does red meat affect the gut microbiome?
Previous research has found that certain metabolites – chemical byproducts of food digestion – are associated with a higher risk of cardiovascular disease. One of these metabolites is trimethylamine N-oxide (TMAO), which is produced by gut bacteria to digest red meat that contains large amounts of the chemical L-carnitine.
High blood levels of TMAO in humans may be associated with a higher risk of cardiovascular disease, chronic kidney disease, and type 2 diabetes. However, whether TMAO and related metabolites derived from L-carnitine could help explain the impact of red meat consumption on cardiovascular risk and could they contribute to heart risk? To what extent the pulse is involved in meat eating, is still unknown.
To understand these questions, the researchers who carried out this study measured the levels of the metabolites in blood samples. They also examined whether blood sugar, inflammation, blood pressure and blood cholesterol might contribute to the high cardiovascular risk associated with red meat consumption.
Study participants included nearly 4,000 of the 5,888 adults who were initially recruited between 1989 and 1990 for the Heart Health Study (CHS). Participants selected for the current study had no clinical cardiovascular disease at the time of CHS enrollment, an observational study of risk factors for cardiovascular disease in adults 65 years of age and older. up.
CHS tracked 5,888 participants selected from four communities: Sacramento, California; Hagerstown, Maryland; Winston-Salem, North Carolina; and Pittsburgh, Pennsylvania. The median age of participants at registration was 73, nearly two-thirds of participants were female, and 88% of participants identified themselves as white. The median follow-up for the participants was 12.5 years and up to 26 years in some cases. At the follow-up appointment, the participants’ medical history, lifestyle, health status, and sociodemographic characteristics – such as household income, education level and age – were assessed.
Several blood biomarkers were measured at the start of the study and again in 1996-1997. Fasting blood samples frozen at -80 ˚C were examined for levels of several gut microbiota associated with red meat consumption including TMAO, gamma-butyrobetaine and crotonobetaine.
In addition, all study participants responded to two validated food frequency questionnaires about their usual dietary habits, including eating red meat, processed meat, fish, and poultry. birds and eggs, at the start of the study and again from 1995 to 1996. For the first time in the questionnaire, participants reported how often, on average, over the previous 12 months, they ate a certain amount of food. Feeds vary from ‘never’ to ‘almost every day or at least five times per week, based on a varied, moderate serving based on food source. The second questionnaire used ten categories of average intake frequency over the past 12 months, from ‘never or less than once per month’ to ‘six+ servings per day,’ with standard serving sizes is determined.
Results of the study
For the current analyses, the researchers compared the risk of cardiovascular disease among participants who ate different types of animal-based foods (e.g., red meat, processed meat, fish, chicken and eggs). They found that eating a lot of meat, especially red and processed meat, was associated with a higher risk of atherosclerotic cardiovascular disease – a 22% higher risk for every 1.1 servings. everyday.
According to the authors, the increase in TMAO and related metabolites found in the blood accounts for about one-tenth of this increased risk. They also note that blood sugar and inflammatory pathways in general may help explain the link between red meat intake and cardiovascular disease.
Blood sugar and inflammation also appear to be more important in linking red meat intake and cardiovascular disease than pathways related to blood cholesterol or blood pressure. Eating fish, poultry, and eggs was not significantly associated with a higher risk of cardiovascular disease.
“Research effort is needed to better understand the potential health effects of L-carnitine and other substances in red meat such as heme iron, which are associated with type 2 diabetes, rather than just focusing on it,” Wang said. into saturated fat.
Limitations of the study
The study had some limitations that could have affected its results. The study is observational, which means it cannot control for all cardiovascular disease risk factors and may not demonstrate cause and effect between meat consumption and cardiovascular disease, or its mediated by chemicals produced by gut bacteria. In addition, food consumption is self-reported so reporting errors can occur. And, because most study participants were older adults, white men and women in the United States, the findings may not apply to younger or more racially diverse populations. .