Advocates have touted arginine as everything from a lifesaving heart medication to a muscle building sports supplement, making it one versatile amino acid. A typical dose of supplemental arginine is 2 grams to 8 grams, according to New York University Langone Medical Center However, there is no known overdose range for the amino acid. Check with your doctor before taking any supplements, especially if you have health problems or are taking other medicines.
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L-arginine is a fairly innocuous substance, with little information available on the potential for overdose. According to a 2010 material safety data sheet for L-arginine, no data has recorded a toxic dose of the substance in animals. Neither do high doses of arginine cause cancer or developmental problems. In some cases, chronic exposure to L-arginine has been shown to cause mutations in mammalian body cells. More research is necessary to determine the potential for arginine toxicity.
Doctors may prescribe an L-arginine supplement in doses up to 15 grams daily for treatment of congestive heart failure, because the arginine helps widen arteries and improve blood flow. While higher doses have not proven toxic, they were not entirely well received, either. A 2004 study in the "Journal of Nutritional Biochemistry" examined the biochemical effects of daily arginine doses ranging from 3 grams to 30 grams. Doses of 21 grams and 30 grams produced adverse effects, most commonly diarrhea.
A prior double-blind trial reported in the "American Journal of Physiology" gave subjects 30 grams per day. The high arginine dose may have resulted in heartburn. The Institute of Medicine has not determined a tolerable upper limit dose for arginine, but it is still possible that the amino acid may be fatal in large doses. Avoid taking any more of the amino acid than your doctor recommends.
Part of the reason people can tolerate L-arginine in very high doses is that the body helps to regulate how much is present at any time. This is known as the arginine paradox. According to University of Milan researcher Francesco Dioguardi, once you take arginine supplements, your body begins to increase release the enzyme arginase around 48 hours later. This enzyme metabolizes, circulating arginine into ornithine and urea for secretion. Therefore, as you consume more arginine, it begins to break down faster in your body.
Though arginine is seemingly safe for adults to consume in high doses, it is not without danger. In 2007, doctors at the University of Florida mistakenly gave a 3-year-old boy a 60-gram intravenous dose of arginine instead of a 5.75-gram dose for a growth hormone test. The boy later died from the overdose of the amino acid. Additionally, you should never take supplemental arginine if you have had a heart attack. A 2006 trial at Johns Hopkins Medical Institutions ended poorly when heart attack survivors were given 9 grams of arginine daily to reduce vascular stiffness. Six participants receiving the arginine supplement died of unknown causes during the trial, while none of the subjects receiving the placebo died. The researchers closed the study and deemed arginine too dangerous to use for post-heart attack therapy.