Arginine is an amino acid found in many foods, including dairy products, meat, poultry, and fish. It plays a role in several important mechanisms in the body, including cell division, wound healing, removal of ammonia from the body, immunity to illness, and the secretion of important hormones.
The body also uses arginine to make nitric oxide (NO), a substance that relaxes blood vessels and also exerts numerous other effects in the body. Based on this, arginine has been proposed as a treatment for various cardiovascular diseases, including congestive heart failure and intermittent claudication, as well as impotence, female sexual dysfunction, interstitial cystitis, and many other conditions. Arginine's potential effects on immunity have also created an interest in using it as part of an "immune cocktail" given to severely ill hospitalized patients and also for preventing colds.
Normally, the body either gets enough arginine from food, or manufactures all it needs from other widely available nutrients. Certain stresses, such as severe burns, infections, and injuries, can deplete your body's supply of arginine. For this reason, arginine (combined with other nutrients) is used in a hospital setting to help enhance recovery from severe injury or illness.
Arginine is found in dairy products, meat, poultry, fish, nuts, and chocolate.
A typical supplemental dosage of arginine is 2 g to 8 g per day. For congestive heart failure, higher dosages up to 15 g have been used in trials.
Warning:Do not try to self-treat congestive heart failure. If you have this condition, be sure to consult your physician before taking any supplements.
What Is the Scientific Evidence for Arginine?
Note:The first three conditions in this section are life-threatening. If you have angina, congestive heart failure, or intermittent claudication, do not attempt to treat yourself with arginine except under physician's supervision.
Congestive Heart Failure
Three small double-blind, placebo-controlled studies enrolling a total of about 70 individuals with congestive heart failure found that oral arginine at a dose of 5 g to 15 g daily could significantly improve symptoms as well as objective measurements of heart function. ^
People with advanced hardening of the arteries, or atherosclerosis, often have difficulty walking because of lack of blood flow to the legs, a condition known as intermittent claudication . Pain may develop after walking less than half a block.
In a double-blind study of 41 individuals, 2 weeks of treatment with a high dose of arginine improved walking distance by 66%; no benefits were seen in the placebo group or a low-dose arginine group. ^ Good results were also seen in another study, although its convoluted design makes interpreting the results somewhat difficult. ^
A double-blind study of 25 individuals with angina pectoris found that treatment with arginine at a dose of 6 g per day improved exercise tolerance, but not objective measurements of heart function. ^ A double-blind, placebo-controlled crossover trial of 36 individuals with heart disease found that use of arginine (along with antioxidant vitamins and minerals) at a daily dose of 6.6 g reduced symptoms of angina. ^
The substance nitric oxide (NO) plays a role in the development of an erection. Dugs like Viagra increase the body's sensitivityto the natural rise in NO that occurs with sexual stimulation. A simpler approach might be to raiselevels of this substance, and one way to accomplish this involves use of the amino acid L-arginine. Oral arginine supplements may increase NO levels in the penis and elsewhere. Based on this, L-arginine has been advertised as "natural Viagra." However, there is as yet little evidence that it works. Drugs based on raising NO levels in the penis have not worked out for pharmaceutical developers; the body seems simply to adjust to the higher levels and maintain the same level of response.
Nonetheless, some small studies have found possible evidence of benefit.
In a double-blind trial, 50 men with erectile dysfunction received either 5 g of arginine per day or placebo for 6 weeks. ^ More men in the treated group experienced improvement in sexual performance than in the placebo group.
A double-blind crossover study of 32 men found no benefit with 1,500 mg of arginine daily for 17 days. ^ However, the lower dose of arginine as well as the shorter course of treatment may explain the discrepancy between these two studies.
Arginine has also been evaluated in combination with the drug yohimbine (as opposed to the herb yohimbe). ^ A double-blind, placebo-controlled trial of 45 men found that one-time use of this combination therapy an hour or two prior to intercourse improved erectile function, especially in those with only moderate erectile dysfunction scores. Arginine and yohimbine were both taken at a dose of 6 g. Note: Do not use the drug yohimbine (or the herb yohimbe) except under physician supervision, as it presents a number of safety risks.
One study supposedly found that arginine plus OPCs can improve male sexual function, but because the study lacked a placebo group it did not, in fact, find anything at all. ^ (For more information on why placebos are necessary, see Why Does This Database Depend on Double-Blind Studies? )
A small, unpublished, double-blind study listed on the manufacturer's website reported benefits with a proprietary combination of arginine and the herbs ginseng , ginkgo , and damiana , and vitamins and minerals . ^
Sexual Dysfunction in Women
Some postmenopausal women have difficulty experiencing sexual arousal . One small double-blind study of yohimbine combined with arginine found an increase in measured physical arousal among 23 women with this condition. ^ However, the women themselves did not report any noticeable subjective effects, suggesting that the effect was slight. In addition, only the combination of yohimbine and arginine produced results; neither substance was effective when taken on its own. Slight benefits were also seen in preliminary double-blind, placebo-controlled trials that evaluated a combination therapy containing arginine, along with the herbs ginseng , ginkgo , and damiana , and vitamins and minerals . ^
Interstitial cystitis is a condition in which an individual feels like he or she has symptoms of a bladder infection, but no infection is present. Medical treatment for this condition is less than satisfactory.
A 3-month, double-blind trial of 53 individuals with interstitial cystitis found only weak indications that arginine might improve symptoms of interstitial cystitis. ^ Several participants dropped out of the study; when this was properly taken into account using a statistical method called ITT analysis, no benefit at all could be proven.
A very small double-blind trial also failed to find evidence of benefit. ^
A 2-month, double-blind study involving 40 children with a history of frequent colds concluded that arginine seemed to provide some protection against respiratory infections . ^ Of the children who were given arginine, 15 stayed well during the 60 days of the study. By contrast, only 5 of the children who took placebo stayed well, a significant difference.
Nutritional Support in Hospitalized Patients
Several nutritional products that contain arginine as well as other substances have been tried in hospital settings to enhance recovery following major surgery , illness, or injury. These mixtures are delivered enterally, which means through a tube into the stomach. A review of 15 studies, about half of them double-blind and involving a total of 1,557 individuals, found that such products can reduce episodes of infection, time on ventilator machines, and length of stay in the hospital. ^ However, because of the many nutrients contained in these so-called immunonutrient mixtures, it is not clear whether arginine deserves the credit.