The amino acid L-arginine provides no benefit to people who have suffered a heart attack, and may even increase the mortality rate in patients over the age of 60, Baltimore-based researchers report.

Based on evidence that L-arginine can have a beneficial effect by reducing the stiffness of blood vessels, Dr. Steven P. Schulman, from Johns Hopkins Hospital, and his associates initiated a clinical trial involving 153 heart attack patients.

The participants were randomly assigned to L-arginine (up to 3 grams three times daily) or to an inactive “placebo” supplement for 6 months after experiencing a first heart attack.

According to the researchers’ report in Wednesday’s Journal of the American Medical Association, follow-up data were obtained for 55 subjects in the L-arginine group and 59 in the placebo group.

There were no significant changes in either group in measures of heart function or artery elasticity.

However, six deaths occurred in the L-arginine group, including five among patients age 60 years or older, and none in the control group, which led to early termination of the trial.

“L-arginine therapy should not be given to patients following a (heart attack),” Schulman’s team advises. Furthermore, they add, “L-arginine therapy in older patients with diffuse atherosclerosis may worsen clinical outcomes.”

SOURCE: Journal of the American Medical Association, January 4, 2006.