Get your blood flowing with L-arginine: popular in heart and sexual health formulas, L-arginine works by improving blood flow in the body. Here's advice on buying and using this truly cutting-edge supplement

THE BASICS: Arginine, an amino acid, or building block of protein, is the only precursor to nitric oxide, one of the body's most important regulatory molecules. (Nitric oxide is not to be confused with nitrous oxide, or laughing gas.) Nitric oxide controls blood vessel tone and flexibility, so it has a profound effect on the cardiovascular system. Arginine's benefits are practically synonymous with nitric oxide, and all of nitric oxide's effects depend on the body's reserves of arginine.

ALIAS: Like many other amino acids, arginine is formally identified as L-arginine. Supplemental L-arginine boosts nitric oxide levels, improving the heart and blood vessels, immunity, neurotransmitter activity, erectile function in men and possibly gastric reflux. The conversion of arginine to nitric oxide requires the enzyme nitric oxide synthase, which requires vitamin C.

HOW THEY WORK: Arginine supplements rapidly boost levels of nitric oxide, which in turn increases blood vessel flexibility and improves blood flow. Arginine is also necessary for normal protein synthesis--important when you consider that after water, most of the body consists of protein. Some arginine is also converted to ornithine, an amino acid needed for the body's production of growth hormone. A small amount of arginine is converted to gamma-aminobutyric acid, a calming neurotransmitter.

HEALTH BENEFITS: Supplemental arginine has several important and varied health benefits.

* Blood vessel tone. Arginine, by way of nitric oxide, regulates the endothelium, a thin layer of cells in blood vessel walls. The endothelium gently expands and contracts, helping the heart move blood throughout the body. Dietary trans fats, especially when combined with refined carbohydrates in fast foods, interfere with normal endothelial activity, leading to "endothelial dysfunction," a risk factor for heart disease. Supplemental arginine can improve endothelial function in patients with heart disease.

* Blood pressure. Arginine supplements have been found to reduce blood pressure, likely as a result of nitric oxide's ability to relax and dilate blood vessels. In one study, supplements of a sustained-release form of arginine (1050mg, twice daily) led to substantial reductions in systolic blood pressure and modest reductions in diastolic blood pressure.

* Erectile dysfunction. The same vascular problems underlying endothelial dysfunction also impact a man's ability to maintain an erection. Supplemental arginine has been shown to improve the ability of blood vessels in the penis to dilate, resulting in firmer erections. The benefits may be enhanced by combining arginine with Pycnogenol, a natural antioxidant.

* Weight management and diabetes. Some evidence suggests that arginine supplements might help improve blood sugar levels and reduce weight. In a study with laboratory rats, supplemental arginine led to a 25 percent decrease in blood sugar levels. In addition, the animals' weight decreased by 16 percent, while the relative weight of muscle, heart and brain tissues increased. These benefits may be related to arginine's role in protein synthesis.

* Immune defense. White blood cells use nitric oxide to kill bacteria, fungi and parasites. This defense extends to protecting the body against cancer-cell formation, and it may eventually be found to attack cancer cells.

BACKGROUND CHECK: In 1992, the journal Science recognized nitric oxide as the "molecule of the year." Three researchers were awarded the Nobel Prize in medicine in 1998 for their work in understanding nitric oxide. Of course, nitric oxide's accolades rest on the foundation of arginine.

HEADS UP: Because arginine boosts nitric oxide levels, it may amplify the effects of nitrate drugs, such as nitroglycerin, resulting in a sudden drop in blood pressure. It is also possible that arginine may stimulate the activity of the herpes virus.

WHAT YOU SHOULD TAKE: As part of a preventive health program, take about 2g daily of arginine between meals. Because arginine is broken down fairly quickly, a sustained-release arginine supplement may provide the most benefits. Men can take another gram or two shortly before sexual intercourse. The benefits of arginine may be enhanced with vitamin C and Pycnogenol.

SEXUAL HEALTH FOR WOMEN , TOO

A double-blind study found that L-arginine helped improved sexual dysfunction in women, when combined with Panax ginseng, ginkgo and other ingredients. A combination product called ArginMax was used in the study.

> The double strength formula of NOW FOODS L-ARGININE (1000MG) provides support to the circulatory system and improves blood flow.

> Solgar L-ARGININE + L-ORNITHINE 500/250MG is easily absorbed because it does not contain peptide bonds.

> Source Naturals L-ARGININE POWDER helps support muscle metabolism and works to relax blood vessels for increased circulation.

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