How Much L-Arginine?

One of the biggest problems with statins is that they are prescribed to lower a perceived risk factor without full consideration to the other effects they have. But the prescription of natural nutritional supplements can also fall into this same trap.

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There are a number of nutritional supplements that have been shown to be much more effective than statins. But I think it is important to also warn people about the potential dangers of some of them.

L-arginine is a widely available nutritional supplement for lowering blood pressure and is often recommended for the prevention of cardiovascular disease. L-arginine is an amino acid that converts into nitric oxide. Nitric oxide is an extremely important substance for dilating the blood vessels and is therefore critical for adequate circulation. Through this mechanism l-arginine does lower blood pressure and may also help with erectile dysfunction.

However, when I interviewed Professor Sherif Sultan, one of the world’s leading vascular and endovascular surgeons, for Statin Nation II, he explained that L-arginine supplementation has been shown to cause a number of adverse effects. L-arginine can cause some types of cancer to spread. Some forms of irregular heartbeat can also be made worse by L-arginine, and L-arginine can actually cause blood pressure to become dangerously low for some people.

A study published in the Journal of the American Medical Association in 2006 looked at the effect of giving L-arginine to patients after they had suffered a heart attack. It found that L-arginine, surprisingly, did not improve vascular stiffness measurements. In fact, six patients in the L-arginine group died during the six-month trial compared with no deaths in the placebo group. The researchers understandably concluded that “L-Arginine should not be recommended following acute myocardial infarction".

The results of this study are in conflict with other studies done on l-arginine by others such as Nobel Prize winning researcher Louis Ignarro. Published in 2004. However, those studies were done on mice instead of humans and they also included other nutrients such as vitamin C that we would expect to have a beneficial effect - the benefit could be from the vitamin C rather than l-arginine.

To add more confusion, a study published in the journal circulation in 1996 found that l-arginine supplementation had beneficial effects for patients with severe heart failure.

In the 2006 study that found l-arginine to be harmful the study participants were given 3grams of l-arganine 3 times a day for 6 months. And in the 1996 study that found a benefit for heart failure patients, a larger amount of l-arginine was used (5.6-12.6grams per day), but just for 6 weeks. So, all of this makes it very difficult to determine an appropriate dose. Obviously it depends very much on the individual person and any existing health conditions. Caution suggests that the dose should be kept below 8grams per day.

Anyone who feels l-arginine is benefiting them personally should also try to investigate if this benefit cannot be attributed to other nutrients they are taking, We cannot yet be sure about the overall effects of l-arginine.


-Long-term combined beneficial effects of physical training and metabolic treatment on atherosclerosis in hypercholesterolemic mice. Proc Natl Acad Sci U S A. 2004 Jun 8; 101(23): 8797–8802. Published online 2004 May 28. doi:  10.1073/pnas.0402734101
PMCID: PMC423275

-Rector TS1, Bank AJ, Mullen KA, Tschumperlin LK, Sih R, Pillai K, Kubo SH. Randomized, double-blind, placebo-controlled study of supplemental oral L-arginine in patients with heart failure. Circulation. 1996 Jun 15;93(12):2135-41.

-Schulman SP, Becker LC, Kass DA, et al. L-Arginine therapy in acute myocardial infarction. The Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial. JAMA. 2006;295(1):58–64. doi:10.1001/jama.295.1.58