What It Is:
L-arginine, also referred to as arginine, is required to carry out the synthesis of nitric oxide, a compound that, working through cGMP, relaxes blood vessels and allows more blood to flow through arteries. It has been hypothesized that taking extra arginine will increase nitric oxide levels and, in turn, increase blood flow to various parts of the body.

What It Does: (See the CL Encyclopedia article on Arginine for more details)
Note: The first three conditions in this section are life-threatening. If you have angina, congestive heart failure, or intermittent claudication, do not attempt to treat yourself with arginine except under physician's supervision.

Congestive Heart Failure (fluid build-up in lungs and legs due to heart weakness)
Several small clinical trials have shown that arginine at doses of 5 grams to 15 grams (1 gram = 1,000 mg) daily may improve symptoms of congestive heart failure as well as objective measures of heart function (Hambrecht, J Am Coll Cardiol 2000).

Angina (chest pain due to reduce blood flow to heart)
Studies have shown improvement in exercise tolerance, although not heart function, in people with angina when taking 6 grams per day of arginine. (Bednarz Int J Cardiol 2000). Another study showed decreased symptoms of angina when 6.6 grams of arginine was taken daily (from a fortified food bar with vitamins and minerals) (Maxwell, J Am Coll Cardiol 2002).

Intermittent Claudication (leg pain during exercise due to insufficient blood flow)
A study showed that 2 weeks of treatment with 6.6 grams of arginine daily (from a fortified food bar with vitamins and minerals) improved walking distance by 66% (Maxwell, Vasc Med 2000). However, a longer (6-month) and better designed study (Wilson, Circulation 2007) found arginine (3 grams per day) to be less effective than placebo.

Sexual Enhancement (See Product Review of Sexual Enhancement Supplements for more information)
Arginine might offer modest benefit for sexual dysfunction in men. Although arginine alone has not been studied as a treatment for sexual dysfunction in women, a small but reasonably good double-blind trial found evidence for benefit with a combination formula (ArginMax for Women) providing a daily dose of 2,500 mg of L-arginine, as well as amounts of herbs and numerous vitamins and minerals

Other Uses
L-arginine may modestly increase exercise endurance in recreational and older athletes, although not in trained athletes. It is widely promoted as a key ingredient in "nitric oxide" supplements, which are touted as increasing muscle size, but clinical evidence does not support this use. (See the Nitric Oxide Supplements Review Article for more information.) 

 

Some evidence suggests that arginine may be helpful in AIDS-related wasting, colds, necrotizing enterocolitis, intolerance to nitrate medication, post-surgery recovery and in improving kidney function in kidney transplant patients treated with cyclosporine. There is also preliminary evidence of a role for arginine in other treating conditions, including senile dementia, hypertension, and sickle cell disease.

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