Study explains why red meat causes heart disease

By Gwyn Wright via SWNS

Red meat causes heart disease because of the way bacteria in the stomach respond to it, according to new research.

The study suggests that gut bacteria produce chemicals that explain some of the link.

For every serving of red meat someone eats on average per day, their risk of getting heart disease rises by 22 percent.

By-products from digestion explain around 10 percent of the elevated risk.

Researchers say new treatments to target the way red meat interacts with the gut are needed.

Earlier research has shown certain chemicals produced when we digest food are associated with a higher risk of heart disease.

One of these is trimethylamine N-oxide (TMNO) which is produced by gut bacteria to digest red meat that contains high amounts of the chemical L-carnitine.

High levels of TMNO in the blood may be associated with a higher risk of heart disease, chronic kidney disease and type two diabetes.

For the study, US researchers measured levels of the by-products in blood samples.

They also probed whether blood sugar, inflammation, blood pressure and blood cholesterol may account for the higher risk of heart disease associated with red meat consumption.

Around 4,000 American adults took part in the study.

Participants had all taken part in the Cardiovascular Health Study between 1989 and 1990, an observational study of risk factors for heart disease among people over 65.

They were all free of heart disease when enrolled in the new study.

Volunteers for the first study were recruited in California, Maryland, North Carolina and Pennsylvania.

The seniors were 73 on average when they enrolled more than 30 years ago, nearly two-thirds of them were women and 88 percent of them were white.

They were followed up for an average of 12 and a half years but some were followed up for 26 years.

At follow-up appointments, their medical history, lifestyle, health conditions, household income, education and age were assessed.

Biological markers of disease in blood were assessed when the study began and again between 1996 and 1997.

Blood samples were frozen at -80˚C before being tested for gut bacteria including TMAO, gamma-butyrobetaine and crotonobetaine.

All participants also answered questionnaires about their diets including how much they ate various types of red meat, fish, poultry and eggs when the study began and again between 1995 and 1996.

In the first questionnaire, participants indicated how often, on average in the previous year, they had eaten given amounts of various foods.

Answer options ranged from “never” to “almost every day or at least five times per week” and were based on medium portion sizes, which varied based on the food source.

The second questionnaire asked them to tick one box about their average intake over the past 12 months, ranging from “never or less than once per month” to “six or more servings per day,” with defined standard portion sizes.

For the current study, the team compared the risk of heart disease among participants who ate different amounts of animal source foods - red meat, processed meat, fish, chicken and eggs.

As well as discovering the link between TMO and other by-products and heart disease, the team also found blood sugar and inflammation pathways could explain some of the link.

Blood sugar and inflammation also appear to be more important in linking red meat intake and heart disease than blood cholesterol or blood pressure.

Intake of fish, poultry and eggs were not significantly linked to higher risk of cardiovascular disease.

Study co-author Dr. Meng Wang from Tufts University in Boston said: “Most of the focus on red meat intake and health has been around dietary saturated fat and blood cholesterol levels.

“Research efforts are needed to better understand the potential health effects of L-carnitine and other substances in red meat such as heme iron, which has been associated with Type 2 diabetes, rather than just focusing on saturated fat.

“Based on our findings, novel interventions may be helpful to target the interactions between red meat and the gut microbiome to help us find ways to reduce cardiovascular risk.”

Heart disease is one of the leading causes of death around the world and the authors say it is the leading cause of death in the US.

The risk of developing heart disease, including heart attack and stroke, increases with age, other risk factors are influenced by an unhealthy lifestyle.

Behaviors known to be good for the heart include eating healthy food, regular exercise, getting enough sleep, keeping a healthy body weight, stopping smoking and controlling high blood pressure, high cholesterol and high blood sugar.

The findings were published in the journal Arteriosclerosis Thrombosis and Vascular Biology.