More than four out of ten American women aged 18 to 59 have some form of sexual dysfunction, as do approximately three out of ten men, according to a study published in the Journal of the American Medical Association last year based on a national survey of more than 3,000 men and women. Among men and women over the age of sixty the problem may be even more widespread. Exactly why impotence, male erectile problems, an inability to orgasm, and other sex-related problems are so prevalent today is the subject of debate. A commonly cited factor is the sex-deadening side effects of Prozac-like antidepressants, as well some 200 other prescription drugs.

One of the most popular new drugs in recent years, Viagra targets sexual dysfunction, though the FDA currently approves its use only for men. (Physicians are free to prescribe it "off-label" for women.) Although Viagra does reduce erectile problems, its adverse side effects include migraines, blurred vision, sinus congestion, and even a potentially fatal sudden drop in blood pressure. Viagra's usefulness for women is under study, with only a few (mostly conflicting) trials being done so far. Unfortunately, compared to men, women may be even more susceptible to Viagra's side effects.  Clearly, safe and effective alternatives to drugs like Viagra would benefit many people. The amino acid L-arginine may be just what the natural doctor ordered.

Arginine plays a number of important roles in the body, including stimulating glands such as the pituitary and thymus. These glandular secretions may affect sperm formation, muscle-building, and immune function. L-arginine may also promote heart health by helping to improve blood cholesterol profiles, relieve heart-related chest pains (angina), and control blood pressure. L-arginine has also been shown to act as a precursor in the body for nitric oxide. A gas molecule, nitric oxide has a number of potential effects on body cells, including the ability to relax arteries and small blood vessels. This can benefit sexual response by maintaining blood flow to the penis or clitoris, for example. Although researchers are still exploring its actions, there is some indication that nitric oxide may also function as a sex-enhancing neurotransmitter.

 

Numerous studies over the past decade have explored the role of nitric oxide in sexual response. Nitric oxide has been shown to increase erections, for example, in primates, dogs, cats, rats, rabbits, and other animals. Animal studies have also determined that long-term oral administration of arginine has potentially beneficial effects on erectile response. As one study concluded, "These data support the possible use of dietary supplements for treatment of erectile dysfunction." A few animal studies have also shown beneficial effects for both nitric oxide and L-arginine on female sexual response.

A more limited number of studies have looked directly at the effects of L-arginine on human sexual response. For example, a small 1994 study in which men took 2.8 grams of arginine every day for two weeks showed a significant improvement in erectile function. Another study found that almost three-quarters of 178 men with low sperm counts had significantly higher counts after taking 4 grams of arginine daily for at least three months. Most recently, a study published in 1999 followed 50 men with erectile dysfunction for six weeks. Among those who took a high (5 grams) daily dose of arginine, 31 percent reported significant subjective improvements in sexual function, compared to only 12 percent of those taking a placebo. Human studies on arginine for women seem to be lacking at this point.

References Chen, J., et al., "Effect of oral administration of high-dose nitric oxide donor L-arginine in men with organic erectile dysfunction: results of a double-blind, randomized, placebo-controlled study," BJU Int, 83(3):269-73 1999 Feb Laumann, E.O., et al., "Sexual dysfunction in the United States: prevalence and predictors, JAMA, 281(6):537-44 1999 Feb 10 Moody, J.A., et al., "Effects of long-term oral administration of L-arginine on the rat erectile response," J Urol, 158(3 Pt 1):942-7 1997 Sep Propper, C.R., and T.B. Dixon, "Differential effects of arginine vasotocin and gonadotropin-releasing hormone on sexual behaviors in an anuran amphibian," Horm Behav, 32(2):99-104 1997 Oct Simonsen, U., et al., "Nitric oxide is involved in the inhibitory neurotransmission and endothelium-dependent relaxations of human small penile arteries," Clin Sci (Colch), 92(3):269-75 1997 Mar Yildiram, S., et al., "The effects of long-term oral administration of L-arginine on the erectile response of rabbits with alloxan-induced diabetes," BJU Int, 83(6):679-85 1999 Apr Zorgniotti, A.W., and E.F. Lizza, "Effect of large doses of the nitric oxide precursor, L-arginine, on erectile dysfunction," Int J Impot Res, Mar 1994, 6(1):33-5; discussion 36

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