Arginine is an amino acid (a building block of protein), produced in the human body and also found in many foods–particularly those rich in protein, such as dairy products, meats, fish, nuts, and soybeans. The majority of the time , we produce or consume all the arginine we need. It serves many functions in the body, but one of its main projects is a precursor for nitric oxide, which consequently can also be vital, especially to cardiovascular wellness as well as the healthy functioning of blood vessels. Arginine is offered as a dietary supplement, usually in a form known as L-arginine, and is found in many formulations promising to promote heart health. To clean the fog of claims and counter-claims, here’s a summary of what is known: Some preliminary studies have found that arginine supplements can improve the function of blood vessels, improve coronary blood flow, lower blood pressure and also reduce angina and other symptoms in individuals with heart or vascular disease. It’s been used to treat heart failure. However, two well-designed studies raised red flags regarding arginine supplements and the heart. One, conducted by researchers at Stanford University and published in Circulation in 2007, discovered that arginine supplements did not help people using the peripheral arterial disease and might even have made matters worse. “Not helpful” was the end. The study needed to be stopped; researchers warned strongly against using arginine for heart attack patients. Furthermore, no evidence supports arginine as a muscle builder or performance enhancer, even though it is in numerous sports nutritional supplements. Arginine supplements (often containing other dubious ingredients) are marketed to improve erections and enhance 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 security is unknown. Briefly boosting nitric oxide might not really benefit individuals with cardiovascular disease, let alone those hoping to avoid it. Excess nitric oxide could have adverse effects. When you have heart disease or are at high risk, you should be under a doctor’s supervision; there are proven drugs that can help. Cardioprotective drugs like statins and ACE inhibitors (such as high blood pressure) increase nitric oxide availability. If you have erectile problems, talk with your doctor. Drugs like sildenafil (Viagra), that boost nitric oxide, may help. But your problem might not be a lack of nitric oxide. Emotional factors can lead to sexual problems.