L-arginine is an amino acid found in foods such as meat, dairy products, poultry and fish. The body uses arginine to make nitric oxide, a substance that relaxes the blood vessels. Arginine appears to be safe at moderate doses of 2 to 3 Grams per day, although minor digestive distress can occur. High doses of arginine may stimulate the body’s production of gastrin, a hormone that increases stomach acid. For this reason, arginine may be harmful for individuals with ulcers and people taking drugs that are hard on the stomach.

L-arginine may also alter potassium levels in the body, especially in people with severe liver disease. It is particularly a concern for people who take drugs that alter potassium levels such as potassium sparing diuretics and ACE inhibitors.

In a double-blind clinical trial, 50 men with problems achieving an erection received either 5 Grams of L-arginine per day or placebo for 6 weeks. More men in the treated group experienced improvement in sexual performance than the placebo.