A team of US scientists has identified a link between a chemical called carnitine, found in red meat, and increased risk of heart disease.

Health researchers have assumed in the past that saturated fat and cholesterol found in red meat increase the risk of heart disease in humans. But this new study, published in Nature Medicine, suggests that the presence of carnitine — found in large quantities in red meat, as well as in dietary supplements and energy drinks — could in fact be to blame.

Carnitine helps the body shift fatty acids into cells, where they can be used as energy. Research performed at the Cleveland Clinic, however, shows that — in both mice and humans — bacteria take the chemical and convert it into something called Trimethylamine N-oxide (TMAO). Sadly, TMAO is a compound that's known to encourage atherosclerosis — which is another name for thickening of the arteries.

The researchers studied the carnitine and TMAO levels in over 2,500 patients, which represented a mixture of omnivores, vegetarians and vegans. The result? Patients with high TMAO levels also had more carnitine in their blood, and were more likely to develop cardiovascular disease, heart attacks, stroke and... death. Not just that, but in vegans, the propensity to convert carnitine to TMAO was diminished. Dr Stanley Hazen, one of the researchers behind the project, expains to the Wall Street Journal:

"Cholesterol is still needed to clog the arteries, but TMAO changes how cholesterol is metabolised like the dimmer on a light switch. It may explain why two people can have the same LDL level [a measure of one type of cholesterol], but one develops cardiovascular disease and the other doesn't. "

The research certainly adds to the ever-expanding body of evidence that suggests red meat isn't good for us. In the short term, then, the advice of the researchers is to cut back on consumption of meats like beef and lamb.

But the finding also promises some good news in the future for carnivores amongst us — because it might be possible to target those bacteria which convert carnitine to TMAO. "In the future, maybe there will be a heart-healthy yogurt, or a drug to block the formation of TMAO," explained Hazen to the Wall Street Journal. And then we can eat as much steak as we like, right? [Nature Medicine via WSJ and BBC]

Image by Max Frank under Creative Commons license