Research conducted at the Cleveland Clinic's Lerner Research Institute and published April 8 in the journal Nature Medicine has pinpointed carnitine for having a role in the development of cardiovascular disease.
Carnitine is a compound found in energy drinks and red meat that also is sold as a dietary supplement.
Carnitine commonly helps the body transport fatty acids into cells to be used as energy. However, Lerner researchers found that in both humans and mice, bacteria in the digestive tract can convert carnitine into a metabolite called TMAO that promotes atherosclerosis, which is hardening or thickening of the arteries.
The researchers examined the records of 2,595 meat eaters and vegetarians undergoing cardiac evaluations and found that patients with high levels of TMAO were more likely to develop cardiovascular disease and suffer heart attacks, strokes and death.
Dr. Stanley Hazen, chief of cellular and molecular medicine at Lerner, said carnitine may be compounding the danger of the cholesterol and saturated fat in beef, pork and other red meat.
However, Dr. Betsy Booren, chief scientist at the American Meat Institute, noted that cardiovascular disease is "a complex condition" that's associated with a number of factors, from genetics to lifestyles, and attempts to link it to "a single compound found at safe levels in red meat oversimplifies" the issue.
It's important to note that there have been many other studies examining carnitine that have not shown adverse effects from the compound at a number of doses, she said, adding that a fact sheet from the National Institutes of Health concludes that carnitine is essential and safe.
In fact, Hazen added that carnitine also is found in nuts, beans, fruits and vegetables and said some energy drinks have more carnitine that a large steak.
Duffy MacKay, vice president for regulatory and scientific affairs at the Council for Responsible Nutrition, which represents energy drink and supplement makers, said the researchers had drawn "large conclusions from small studies" of humans and mice, and the concept that one compound in one's diet is responsible for cardiovascular disease "is questionable."
The fact sheet from the National Institutes of Health, which sponsored the study, is available at www.ods.od.nih.gov/factsheets/Carnitine-HealthProfessional.