The mainstream success of Viagra, the drug for erectile difficulties, brought a previously quiet problem to the forefront of health issues. Until recently, many Americans perceived sexual dysfunction as something that affected a few unlucky men. In fact, significantly more women than men suffer from the condition. According to an article in the Journal of the American Medical Association, a surprising 43 percent of women and 31 percent of men in the United States experience sexual dysfunction.1 And with the currently aging boomer population, that number can only be expected to increase rapidly.
Viagra?s popularity has not gone unnoticed by natural products manufacturers. The market is flooded with natural sexual-performance products offering alternativesâin part because Viagra is expensive, can have harmful side effects, does not address other issues such as libido, and isn?t intended for women.
Causes and symptoms
For women, symptoms of sexual dysfunction can include decreased libido, vaginal dryness and an inability to become aroused or achieve orgasm. The cause is often hormonal, many times triggered by menopause when estrogen and testosterone levels drop.2 Estrogen plays a key role in vaginal lubrication and genital blood flow. Androgenic hormones such as testosterone affect sexual desire, arousal and orgasm by modulating nitric oxide, a chemical that causes the smooth-muscle relaxation necessary for arousal in both men and women.3 Other causes of female sexual dysfunction include prescription medications (such as hormone replacement therapy), hysterectomy and psychological issues.
Men?s sexual dysfunction can include decreased libido, premature ejaculation and erectile dysfunction (impotence). The most common ailment is secondary erectile dysfunction, when a man can no longer achieve and maintain an erection. It is almost always physiological in basis and results when the blood flow to the penis is interrupted. The most common cause is age, which decreases blood-vessel dilation and smooth-muscle relaxation, preventing the blood from becoming trapped in the penis. Other factors include smoking, diabetes, and neurological and hormonal disorders. Low testosterone levels or psychological factors can cause low libido, whereas premature ejaculation is almost always psychologically based.4
Ironic as it is considering the statistics, most of the research and products are geared toward men. But this is changing. Retailers shopping for a sexual-performance inventory can now find products that treat just about every aspect of the dysfunction for both sexes. Sorting through manufacturer claims, however, can be overwhelming. Following is a list of ingredients that show promise for the treatment of sexual performance problems.
Ginkgo (Ginkgo biloba)
Ginkgo is now often included in sexual-enhancement products because of a study showing that the botanical relieved sexual dysfunction caused by antidepressants.5 In this open-label (not blinded) clinical trial, 33 women and 30 men (all taking antidepressants and all experiencing sexual dysfunction) took a range of ginkgo from 60 mg to 120 mg twice daily, with an average of 209 mg per day. Of the subjects, 91 percent of the women and 76 percent of the men reported improved sexual function. The subjects reported increases in desire, excitement (lubrication and arousal) and orgasm. Ginkgo probably works by improving circulation as well as neurotransmitter and nitric oxide modulation.
It should be noted that a later placebo-controlled study failed to repeat earlier positive findings.6 It did find, however, that both the placebo group and the Ginkgo group showed improvement in some part of sexual function, suggesting the prevalence of placebo effect in assessing sexual function.
Ginseng (Panax ginseng, Panax quinquefolium)
Ginseng is perhaps the best-known Asian herb in the West. It is commonly used for energy, stamina and enhanced sexual performance. Yet surprisingly little research has been done on the botanical?s ability to enhance sexual performance. The studies that have been doneâon both Asian (Panax ginseng) and American (Panax quinquefolium) ginsengâdo show positive results.
A double-blind, placebo-controlled study demonstrated that when male human subjects took 900 mg of Korean red ginseng (Panax ginseng) three times daily, they produced more erections, maintained them longer and experienced increased penile rigidity.7
Women may also benefit from ginseng. It has been shown to dilate genital blood vessels during arousal and may help lessen menopausal symptoms such as fatigue and depression, which may affect libido.8,9
Scientists are still studying what ginseng properties allow it to work for sexual performance. Researchers at Southern Illinois University in Springfield speculate that the plant does not moderate hormones, but that its ginsenosides components affect the nitric oxide mechanism, the central nervous system and vasodilatation.10
This amino acid is a precursor to nitric oxide, which, as explained above, aids sexual function by initiating the smooth-muscle relaxation necessary for sexual arousal.11
One study found that when postmenopausal women were given 6 g of L- arginine in combination with 6 mg of yohimbine (Pausinystalia yohimbe, see below), they experienced increased sexual arousal.12 Nitric oxide has Also been shown to increase vaginal blood flow, which augments arousal.13 Another study on women reported that 34 subjects who took four weeks of ArginMax, a proprietary supplement containing L-arginine, damiana (Turnera diffusa), ginkgo, ginseng, vitamins and minerals, reported improvement in sexual desire, frequency of intercourse and increased clitoral stimulation, as well as a reduction of vaginal dryness.14
L-arginine may also be useful in erectile dysfunction. One open-label, non-placebo-controlled study found that when 40 human male subjects without confirmed erectile dysfunction took 1.7 grams of L-arginine daily for three months along with increasing doses of pycnogenol for two of the three months, 92 percent experienced normal erection.15
Maca root (Lepidium meyenii Walp)
Maca is a tuber that grows in the Peruvian Andes where its traditional uses include improving fertility and libido. Encouraging recent studies demonstrate that the plant may, indeed, enhance sexual performance.
A study published in Urology reported that maca enhanced the sexual function of mice and rats.16 After receiving 22 days of a maca extraction standardized for the fatty acids macaene and macamide, one male mouse taken from the experimental group and placed with two female mice completed sexual intercourse 67 times in a 3-hour period, compared with the same number of mice in the control group that had sexual intercourse 21 times in the same time period. The study Also found that a group of maca-fed mice with erectile dysfunction experienced a decrease in the latent period of erection after ingesting maca for 22 days. These findings demonstrate that maca may be useful for healthy mice and perhaps humans, including those with erectile dysfunction.
Also proved to increase sexual desire in male humans. In a 12-week, double-blind, placebo-controlled study, 30 men received 1,500 mg of maca daily and 15 men received 3,000 mg of maca daily.17 Beginning at eight weeks, the maca groups reported increases in libido; none of the placebo group reported an increase. Results did not appear to be dose-dependent. The maca subjects? testosterone levels did not increase and maca did not affect anxiety or depression levels. The scientists, however, are unsure how maca works. It is speculated that the two novel maca constituents mentioned above, macamides and macaenes, may be responsible. One study found that maca extracted with hexane improved rat sexual performance more effectively than those extracted using methanol or chloroform.18
Yohimbine (Pausinystalia yohimbe)
The bark of this West African tree contains alkaloids that are traditionally used as aphrodisiacs for both men and women. Although no studies have demonstrated its ability to increase sex drive, yohimbine has been shown clinically to effectively treat erectile dysfunction. The plant?s active constituent is an adrenergic agent (in this case, adrenergic refers to the release of the hormone norepinephrine), effectively increasing levels of norepinephrine, which is connected to sexual function in the hypothalamus. Yohimbine?s adrenergic effects Also modify the activity of nerve receptors, allowing them to remain ?stimulated.? 19
One 10-week, placebo-controlled, double-blind human study found that yohimbine is a safe and effective treatment for psychologically based erectile dysfunction.20 A group of 48 men took 18 mg of yohimbine a day for 10 weeks. At the end, 62 percent of the yohimbine group reported some improvement in sexual function versus 21 percent in the placebo group. Another human study found that yohimbine was effective in the treatment of men with mild secondary erectile dysfunction.21 Half of 18 men given yohimbine were successful in completing intercourse in more than 75 percent of attempts. Those with less severe erectile dysfunction had more success. A study done on dogs found that yohimbine increased the time of full erection, delayed ejaculation and produced a decrease in pelvic-thrusting behavior in the animals, which resulted in less stimulation and longer erection. 22
As an added benefit, yohimbine may hold promise for men experiencing erectile dysfunction and decreased libido as a side effect from the antidepressant fluoxetine (Prozac). Eight out of nine patients taking the antidepressant and treated for sexual dysfunction with yohimbine reported improvement in sexual function, but five patients discontinued the treatment due to side effects.23 It should be stated, however, that this study was based on limited case reports and that further controlled studies are warranted since this study is 12 years old.
Lastly, yohimbine is not without negative side effects. The plant has been shown to increase blood pressure in untreated hypertension patients and Also to increase heart rate and cause dizziness.27
Botanicals and supplements offer promising treatment for sexual-performance problems, although more human research with well-designed studies is necessary. Retailers may want to recommend blends, considering the success of ArginMax and the study on L-arginine and yohimbine, as well as L-arginine and pycnogenol. Although ginkgo, ginseng and L-arginine (and perhaps yohimbine) all appear to treat female sexual problems, more research into ingredients to treat women?s sexual dysfunctions is sorely needed. Botanicals such as damiana and muira puama (Ptychopetalum olacoides) may be common ingredients in female sexual performance products, but research there is lacking. As scientists continue to unfold the mystery of how specific chemicals such as nitric oxide affect human sexuality and how the brain is involved in the process, research can better target ingredients that directly affect this process.
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13. Kim SW, et al. An in-vivo rat model to investigate female vaginal arousal response. Jurol 2004;171(3):1357-61.
14. Ito TY, et al. A double-blind placebo-controlled study of ArginMax, a nutritional supplement for enhancement of female sexual function. J Sex Marital Ther 2001;27(5):541-49.
15. Stanislavov R, et al. Treatment of erectile dysfunction with Pycnogenol and L-arginine. J Sex Marital Ther 2003;29(3):207-13.
16. Zheng BL, et al. Effect of a lipidic extract from Lepidium meyenii on sexual behavior in mice and rats. Urology 2000;55(4):598-602.
17. Gonzales GF, et al. Effect of Lepidium meyenii (MACA) on sexual desire and its absent relationship with serum testosterone levels in adult healthy men. Andrologia 2002;34(6):367-72.
18. Cicero AF, et al. Hexanic maca extract improves rat sexual performance more effectively than methanolic and chloroformic maca extracts. Andrologia 2002;34(3):177-9.
19. Grossman E, et al. Oral yohimbine increases blood pressure and sympathetic nervous outflow in hypertensive patients. Cardiovasc Pharmacol 1993;22:22-6.
20. Reid K, et al. Double-blind trial of yohimbine in treatment of psychogenic impotence. Lancet 1987;2(8556):421-3.
21. Guay AT, et al. Yohimbine treatment of organic erectile dysfunction in a dose-escalation trial. Int J Impot Res 2002;4(1):25-31.
22. Yonezawa A. Differential effects of yohimbine, naloxone and 8-OH-DPAT on ejaculatory response in male dogs. Methods Find Exp Clin Pharmacol 2004;26(1):47-51.
23. Hollander E, et al. Yohimbine treatment of sexual side effects induced by serotonin reuptake blockers. J Clin Psychiatry 1992;53(6):207-9.
24. Teloken C et al. Therapeutic effects of high-dose yohimbine hydrochloride on organic erectile dysfunction. J Urology 1998;159:122-4.
25. Kunelius P, et al. Is high-dose yohimbine hydrochloride effective in the treatment of mixed-type impotence? A prospective, randomized, controlled, double-blind crossover study. Urology 1997;49:441-4.
26. Knoll LD, et al. A randomized crossover study using yohimbine and isoxsuprine versus pentoxyfylline in the management of vasculogenic impotence. J Urology 1996;155:144-6.
27. Musso NR, et al. Yohimbine effects on blood pressure and plasma catecholamines in human hypertension. Amer J Hypertension 1995;8:565-71.
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