L-arginine may be harmful for heart attack patients
more harm than good, according to a new study.
The amino acid is a precursor for nitric oxide, which has been shown to lower blood pressure, reduce blood clotting and protect against myocardial infarction and strokes.
It has therefore been recommended in supplement form to people with problems like angina, hypertension and heart failure.
But a new study carried out at John Hopkins in the US is the first to suggest a harmful role for the amino acid.
"L-Arginine does not improve vascular stiffness measurements or ejection fraction and may be associated with higher post-infarction mortality," wrote lead author Steven Schulman of the John Hopkins Medical Institutions, Baltimore.
Patients for the Vascular Interaction with Age in Myocardial Infarction (VINTAGE MI) clinical trial were enrolled between February 2002 and June 2004, and the results were published in the January issue of the Journal of the American Medical Association (Vol. 295, pp. 58-64).
The double-blind, randomised study followed 153 patients with an average age of 60 for six months. One group was given a placebo, while the others were given 9g daily doses of L-arginine.
The results were quantified in terms of vascular stiffness and left ventricle ejection volume.
"There was no significant change from baseline to 6 months in the vascular stiffness measurements or left ventricular ejection fraction in either of the 2 groups, including those 60 years or older and the entire study group," said the researchers.
Six patients actually died from the L-arginine group compared to no deaths in the placebo-group, leading to the study being prematurely terminated amid health concerns.
"These findings have broad public health implications given the increasing availability and use of L-arginine in patients with and without established cardiovascular diseases," wrote Schulman.
The new findings are in stark contrast to previous studies, including research from UCLA Nobel laureate Louis Ignarro, which have shown positive links between L-arginine and heart health.
Ignarro and co-workers showed supplementing the diet of mice with the amino acid, vitamin C and E, reduced artery hardening.
A joint study from Pennsylvania State University, Kraft Foods and INRA in France reported that L-arginine supplements reduced the levels of the heart disease marker homocysteine.
