What Arginine Can—and Can’t—Do
Arginine is an amino acid (a building block of protein) produced in the body and found in many foods. Should you also take a supplement?
Most of the time, we produce or consume all the arginine we need, mostly from foods rich in protein, such as dairy products, meats, fish, nuts and soybeans. It serves many purposes in the body, but one of its most important jobs is to increase production of nitric oxide, which in turn is also vital, particularly to cardiovascular health and the healthy functioning of blood vessels.
Arginine is sold as a dietary supplement, usually in a form called L-arginine. Marketers warn of shortages in the body and say that arginine supplements will improve liver function, build muscles and enhance exercise performance, among other things. The supplements have been seriously studied as treatment for heart disease, erectile problems, headaches and a host of other ills.
A summary of research:
• Preliminary studies have found that arginine supplements can improve the function of blood vessels, enhance coronary blood flow, lower blood pressure and even reduce angina and other symptoms in people with heart and/or vascular disease. There’s evidence it can be used to treat heart failure.
• However, two well-designed studies raised red flags about arginine supplements and the heart. One, conducted by researchers at Stanford University, found that arginine supplements did not help people with peripheral arterial disease and may even have made matters worse. And a study at Johns Hopkins Hospital found that arginine supplements given to heart attack patients dramatically increased deaths. The study had to be halted; researchers warned strongly against using arginine for heart attack patients.
• Some evidence suggests that arginine combined with ibuprofen may ease migraine or dental pain. But more research is needed.
• Claims are made that arginine supplements can prevent or treat diabetes, but there’s no convincing evidence for this.
• 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 make a difference. Indeed, some studies have found little or no improvement, compared to a placebo.
• No evidence supports arginine as a muscle builder or performance enhancer, though it is in countless sports supplements.
• Arginine supplements have been shown to worsen asthma symptoms and increase lung inflammation.
• The benefits of arginine supplements are uncertain, and their long-term safety is unknown. Healthy people do not need them. Briefly boosting nitric oxide may not actually benefit people with cardiovascular disease, let alone those hoping to avoid it. Excess nitric oxide could have adverse effects.
• If you have heart disease or are at high risk, you should be under a doctor’s supervision; there are proven drugs that can help. Cardio-protective drugs such as statins and ACE inhibitors (for high blood pressure) increase nitric oxide availability.
• If you have erectile problems, talk to your doctor. Drugs such as sildenafil (Viagra), which boost nitric oxide, may help. But your problem may not be a shortage of nitric oxide. Many medical and emotional factors can contribute to sexual problems. Arginine supplements are not known to be effective.
• To protect your blood vessels and keep them in good shape, exercise is the best option. Among its many cardiovascular benefits, it probably boosts nitric oxide production.
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