Red meat and cardiovascular diseases: the role of the gut microbiota
Why do red meat lovers have a higher cardiovascular risk? Probably because of their increased blood TMAO levels, a molecule produced by gut microbiota bacteria, according to a study published in the European Heart Journal.
The gut microbiota has already been shown in animal models to be associated to an increased risk of life-threatening cardiac events. Some gut bacteria have the ability to degrade three substances (choline, phosphatidylcholine and carnitine) found in eggs, and mainly in red meat. The product of this degradation is then transported to the liver, where it is transformed into trimethylamine N‑oxide (TMAO), a highly pro-inflammatory molecule that accelerates the development of atherosclerosis*, which is one of the well-known risk factors for cardiovascular diseases. A diet rich in meat, eggs and more generally in TMAO precursors, could thus lead to increased cardiovascular risk.
Comparison of 3 diets
To assess this hypothesis, 113 volunteers were given three diets with the same caloric value containing a quarter of proteins from three different sources: red meat, white meat (poultry) or plant foods (pulses, nuts, seeds). Each participant followed the three diets during four-week periods, separated by “washout” periods lasting from 2 to 7 weeks during which they followed a normal diet. Blood and urine TMAO levels were measured during each of the three diets.
Spare your microbiota an excess of red meat
After a month, blood TMAO levels were three times higher in the “red meat” group than in the other two groups. This increase was caused by the higher production of TMAO by gut bacteria from the carnitine present in red meat, and to the lower excretion of TMAO by the kidney. The good news is that the TMAO increase is completely reversible and disappears quickly once red meat is substituted with white meat or plant proteins. According to the authors, these findings explain the increased risk of cardiovascular diseases and premature death observed in avid eaters of red meat and cold cuts. Changing your diet could be a simple way to preserve your microbiota and prevent this risk.
*fatty plaques on the inner lining of arteries that lead to blood flow obstruction and blood vessel hardening
Wang Z et Bergeron N, Levison BS et al. Impact of chronic dietary red meat, white meat, or non-meat protein on trimethylamine N-oxide metabolism and renal excretion in healthy men and women. European Heart Journal (2018) 00, 1–13 doi:10.1093/eurheartj/ehy799