The majority of the time we create or consume all the arginine we want. It serves many purposes in the human body, but one of its most important projects is a precursor to nitric oxide, which in turn can also be vital, particularly to cardiovascular health as well as the healthy functioning of arteries. Arginine is offered as a dietary supplement, usually in a kind called L-arginine, and is found in many formulations promising to promote heart health. To clear the fog of claims and counter-claims, here’s a summary of what’s known: Some preliminary studies have found that arginine supplements may improve the function of blood vessels, enhance coronary blood flow, lower blood pressure and also reduce angina and other symptoms in individuals with heart or vascular disease. It’s been used as a treatment for heart failure. But two well-designed studies raised red flags regarding arginine supplements as well as the heart. One, conducted by researchers at Stanford University and published in Circulation in 2007, found that arginine supplements did not help people using the peripheral arterial disease and may even have made things worse. “Not useful” was the conclusion. Moreover, no evidence supports arginine for a muscle builder or performance enhancer, even though it’s in countless sports supplements. Arginine supplements (often featuring other questionable ingredients) are marketed to improve erections and improve libido, but it’s not known whether enough arginine gets to blood vessels in the penis to create a difference. Indeed, some studies have found little or no improvement, compared to a placebo. Bottom line: The advantages of arginine supplements are unclear, and their long-term safety is unknown. Briefly boosting nitric oxide may not actually benefit people with cardiovascular disease, let alone those hoping to avoid it. Excess nitric oxide might have adverse results. When you have heart disease or are at high risk, you should be under a physician’s supervision; you will find proven drugs which may help. Cardioprotective drugs such as statins and ACE inhibitors (for high blood pressure) boost nitric oxide availability. If you’ve got erectile dysfunction difficulties, speak to your doctor. Drugs such as sildenafil (Viagra), that raise nitric oxide, may help. But your issue may not be a lack of nitric oxide. Emotional factors can contribute to sexual problems.