US - High levels of red meat consumption could increase the risk of cardiovascular disease according to new research, writes Chris Harris.
The study by Stanley L Hazen from the Cleveland Clinic Lerner Research Institute and others shows that intestinal microbiota can contribute to the link between red meat eating and cardiovascular disease.
However, the study has been criticised by meat industry organisation claiming the findings oversimplify the issue.
American Meat Institute Foundation Chief Scientist Dr Betsy Booren, said: "Cardiovascular disease or CVD is a complex condition that appears to have a variety of factors associated with it, from genetics to lifestyle. Attempts to link cardiovascular disease to a single compound that is found at safe levels in red meat oversimplifies this complex disease.
"In fact, the study's authors themselves say red meat is not to blame, but rather argue that excessive supplementation with L-carnitine that is found at safe and healthy levels in red meat may be a concern. It is important to keep in mind that there are many other studies done on L-carnitine that do not show any adverse health effects at a variety of doses. In fact, the National Institutes of Health fact sheet on L-carnitine shows it is safe and essential.
"A look at the full body of research into cardiovascular disease and diet will show that red meat can be enjoyed for its good taste and nutrition as part of a healthy, balanced diet. Federal nutrition data shows that the protein group is the only food group consumed at proper levels and that Americans, on average, consume the recommended amount of meat.
"This study should not prompt any dietary changes and consumers who enjoy red meat should continue to do so with confidence."
The research team of Robert A Koeth, Zeneng Wang, Bruce S Levison, Jennifer A Buffa, Elin Org, Brendan T Sheehy, Earl B Britt, Xiaoming Fu, Yuping Wu, Lin Li, Jonathan D Smith, Joseph A DiDonato, Jun Chen, Hongzhe Li, Gary D Wu, James D Lewis, Manya Warrier, J Mark Brown, Ronald M Krauss,W H Wilson Tang, Frederic D Bushman, Aldons J Lusis and Stanley L Hazen said that the metabolism by intestinal microbiota of dietary l-carnitine, a trimethylamine abundant in red meat, also produces TMAO and accelerates atherosclerosis in mice.
Intestinal microbiota metabolism of choline and phosphatidylcholine produces trimethylamine (TMA), which is further metabolised to a proatherogenic species, trimethylamine-N-oxide (TMAO).
The research found that people who eat meat in their diets produced more TMAO than vegans or vegetarians following ingestion of l-carnitine through a microbiota-dependent mechanism.
The presence of specific bacterial taxa in human faeces was associated with both plasma TMAO concentration and dietary status the study showed.
Plasma l-carnitine levels in subjects undergoing cardiac evaluation (n = 2,595) predicted increased risks for both prevalent cardiovascular disease (CVD) and incident major adverse cardiac events (myocardial infarction, stroke or death), but only among subjects with concurrently high TMAO levels.
Chronic dietary l-carnitine supplementation in mice altered cecal microbial composition, markedly enhanced synthesis of TMA and TMAO, and increased atherosclerosis, but this did not occur if intestinal microbiota was concurrently suppressed.
In mice with an intact intestinal microbiota, dietary supplementation with TMAO or either carnitine or choline reduced in vivo reverse cholesterol transport.
Intestinal microbiota may thus contribute to the well-established link between high levels of red meat consumption and cardiovascular disease risk, the report which is published in the journal Nature Medicine, concludes.
Further ReadingYou can view the full report by clicking here.
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