Red meat, while part of most people’s diets, is recommended not eat too much of because of its link with colorectal cancer and heart disease.
Recent research has raised the ante when it comes to the risk of heart disease. And it is to do with a chemical called trimethylamine N-oxide (TMAO) made in the gut by bacteria.
TMAO is a natural by-product made during digestion derived from nutrients that are abundant in red meat. TMAO levels are higher in people with cardiovascular disease so it could be the red meat in their diet is partly contributing to this.
To tease out the links between red meat and TMAO production, 113 healthy men and women took part in a clinical trial where they ate different types of dietary protein from red meat, white meat and non-meat protein. Each person followed the special diet for four weeks and then switched to another source of protein with the number of calories kept constant.
When on the red meat diet, blood levels of TMAO were three-times higher compared to diets high in white meat or non-meat protein sources. A novel twist to the study was that half of the people were also placed on high-fat versions of the three diets. The effect of red meat on TMAO was still the same irrespective of how much fat was eaten.
The positive news from the study was that TMAO levels rapidly declined when people switched off the high red meat diet.
How TMAO can raise the risk of heart disease is complex. Previous research has found TMAO can increase cholesterol deposits in artery walls leading to atherosclerosis. TMAO has also been found to increase the clotting ability of blood platelet cells raising the risk of heart attack and stroke.
Measuring TMAO blood levels may be a promising new target to assess the risk of cardiovascular disease and to help with individualising dietary advice for prevention.
The research so far is not saying that red meat should be completely avoided, but instead to take the findings in the context of what is known as a ‘heart healthy’ diet which includes plenty of vegetables, fruits, wholegrains, and plant-based protein sources such as beans, soy and peas.