TUESDAY, Jan. 3, 2006 (HealthDay News) -- Taking the widely used amino acid supplement L-arginine after a heart attack does not improve cardiac function, and could be associated with an increased risk of death, a new study finds.
L-arginine is touted to have benefits for people with high blood pressure, angina, heart failure and sexual dysfunction. Earlier studies have suggested that L-arginine has the potential to reduce blood vessel stiffness.
The latest report, which runs counter to that research, appears in the Jan. 4 issue of the Journal of the American Medical Association and comes from a clinical trial that was ended early after six patients died.
"L-arginine administration did not improve cardiac remodeling over a six-month period," said study co-author Dr. Gary Gerstenblith, a professor of medicine at Johns Hopkins Medical School in Baltimore. "L-arginine does not have a benefit on cardiac function."
The researchers had hoped that L-arginine would promote nitric oxide availability, which could decrease the load on the heart and cardiac vessels as the heart healed after a heart attack. "Our hypothesis was that L-arginine would be beneficial," Gerstenblith said.
In their study, Gerstenblith and his colleagues randomly assigned 153 heart attack patients either 3 grams of L-arginine or a placebo daily for six months. At six months, the researchers found that L-arginine did not reduce vascular stiffness, improve ejection-fraction, or improve clinical outcomes.
In fact, they found an increased risk of death in older patients taking L-arginine compared with those taking a placebo. Six patients in the L-arginine group died during the six-month study period, while none in the placebo group died. This led the researchers to end the trial early.
"L-arginine therapy should not be given to patients following a myocardial infarction," the authors wrote. "It neither alters noninvasive measures of vascular stiffness nor improves left ventricular function. L-arginine therapy in older patients with diffuse atherosclerosis may worsen clinical outcomes."
One expert who has done his own research in the cardiac benefits of L-arginine thinks the reason L-arginine had no effect was because the dosage was too low.
"In our study, we thought you needed to give about 20 grams of L-arginine a day to have an effect," said Dr. Stuart D. Katz, an associate professor of internal medicine at Yale University School of Medicine. "We couldn't come up with a reasonable way to give the 20 grams."
Katz pointed out that taking 20 grams of L-arginine a day would require 40 capsules. "Nobody is going to take 40 capsules a day," he said. "We gave up because we didn't think there was a way to deliver the dose that was likely to be beneficial."
Because the doses in the current study had no effect on blood levels of L-arginine, Katz doesn't think that L-arginine was involved in the increased mortality among patients taking it. "It may have just been chance," he said.
Whether that dose could be harmful is unknown, Katz added. But given the findings in this study, it is possible.
"It raises a flag of caution that this supplement and, perhaps, other supplements need to be evaluated carefully," he said. "I would not recommend using L-arginine supplements as a means to improve cardiovascular health, based on this study."
The American Heart Association can tell you more about heart attacks.