chemical products produced in the digestive tract by gut microbes after eating red meat can help explain part of the increased risk of cardiovascular disease (CVD) associated with the consumption of this food, according to a new study published in the scientific journal “Arteriosclerosis, thrombosis and vascular biology”.
Worldwide, cardiovascular disease is the leading cause of death. Although the risk of developing cardiovascular disease, especially heart attack and stroke, increases with age, other risk factors are influenced by the lifestyle.
Lifestyle and behaviors known to improve cardiovascular health include eating healthy foods, especially fruits and vegetables; regular physical activity; get enough sleep; maintaining a healthy weight; stop smoking; and control high blood pressure, high cholesterol and blood sugar.
Previous research has shown that certain metabolites (chemical by-products of food digestion) are associated at an increased risk of cardiovascular disease. One of these metabolites is TMAO, or trimethylamine N-oxide, which is produced by gut bacteria to digest red meat that contains high amounts of the chemical L-carnitine.
The bone high levels of TMAO in the blood humans can be associated at an increased risk of cardiovascular disease, chronic kidney disease and type 2 diabetes. However, it remains unclear whether TMAO and related L-carnitine-derived metabolites may help explain the effects of red meat consumption on cardiovascular risk, and to what extent they may contribute to the cardiovascular risk associated with meat consumption.
Nearly 4,000 attendees
To understand these questions, the researchers who conducted this study measured the levels of the metabolites in blood samples. They also looked at whether blood sugar, inflammation, blood pressure and blood cholesterol could explain the elevated cardiovascular risk associated with red meat consumption.
Study participants they were nearly 4,000 out of the 5,888 adults initially recruited between 1989 and 1990 for the US Heart Health Study. Participants selected for this study were free of clinical cardiovascular disease at the time of registration.
The average age of the participants at the time of registration was 73 years old, nearly two-thirds of the participants were women, and 88% of participants identified as white. The median duration of participant follow-up was 12.5 years, and up to 26 years in some cases.
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Participants’ medical histories, lifestyle, health conditions, and sociodemographic characteristics, such as family income, education, and age, were assessed during follow-up appointments.
Various blood biomarkers were measured at the start of the study and again in 1996-1997. Fasting blood samples stored frozen at -80°C were tested for levels of several gut microbiomes associated with red meat consumption, including TMAO, gamma-butyrobetaine, and crotonobetaine.
In addition, all study participants completed two validated food frequency questionnaires about their usual eating habits, including the consumption of red meat, processed meat, fish, poultry and eggs, at the start of the study and again between 1995 and 1996.
In the first questionnaire, participants indicated how often, on average, over the past 12 months they consumed certain amounts of various foods, ranging from “never” to “almost every day or at least five times a week”. based on average portion sizes, which varied by food source.
In the second questionnaire, a frequency of ten categories of average intake over the past 12 months was used, ranging from “never or less than once a month” to “more than six servings a day”, with sizes of defined standard portions. For the analyses, the researchers compared the risk of cardiovascular disease among participants who ate different amounts of animal foods (i.e. red meat, processed meat, fish, chicken and eggs).
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discovered that eating more meat, especially red meat and processed meat, was linked to an increased risk of atherosclerotic cardiovascular disease: 22% increased risk for every 1.1 servings per day.
According to the authors, the increase in TMAO and related metabolites found in the blood explained approximately a tenth of this high risk. They also noted that blood sugar and general pathways of inflammation may help explain the links between red meat consumption and cardiovascular disease.
Blood sugar and inflammation also appear to be more important in the relationship between red meat consumption and cardiovascular disease. as pathways related to blood cholesterol or blood pressure. Consumption of fish, poultry and eggs was not significantly associated with an increased risk of cardiovascular disease.
“Research is needed to better understand the potential health effects of L-carnitine and other substances found in red meat, such as heme iron, which have been linked to type 2 diabetes, rather than just focus on saturated fat,” says Wang.