L-Carnitine linked to Heart Disease

Nutrition experts recommend reducing intake of red meat in the diet because it is high in cholesterol and saturated fat, which promotes coronary artery disease. A Cleveland Clinic study led by Stanley Hazen found that carnitine, a popular athletic supplement and component of red meat, also triggers heart disease. Bacteria in the gut break down carnitine to trimethylamine-N-oxide (TMAO), which promotes arterial disease by increasing cholesterol deposits in the arteries. High TMAO in the blood was a good predictor of heart attack and stroke. A study by the same research group showed that gut microbes also metabolized phosphatidylcholine, another athletic supplement, to TMOA. Administration of antibiotics decreased TMOA levels. Carnitine is a popular athletic supplement. However, a joint position statement from the American Dietetic Association and the Dietitians of Canada concluded that carnitine does not improve athletic performance. It might also promote heart disease. 

Further research is warranted. (Nature Medicine, 19:576-585; New England Journal of Medicine, 368: 1575-1584)