Human sexual activity serves both to provide erotic experience and as a means of maintaining the species (reproduction). Regardless of sexual identity or preferred sexual behaviour(s), men and women each have certain physical and psychological requisites for healthy sexual function.
The human sexual response cycle is traditionally defined by four stages - excitement, plateau, orgasm, and resolution. An evolved model of the human sexual response now also takes into account emotional intimacy, sexual stimuli, sexual desire, and emotional and physical satisfaction (Basson, 2001).
Libido, or interest in sex, may be stimulated by sensory experiences – especially sight, smell and touch, or may be more spontaneous via memory, fantasy or thought. For these experiences to result in sexual arousal requires complex interactions throughout the body's central nervous and endocrine (hormonal) systems. Sexual arousal, though no less complex, is more tangible; when a man is aroused, for example, his penis becomes erect. Sexual activity will often result in orgasm for both men and women, after which there is a period of what is called “resolution.”
For normal sexual function, a man must have an intact libido (an ability to become interested in sex), must be able to develop and sustain an erection, must be able to ejaculate (orgasm), and finally, during resolution, the penis must return to its non-erect state.
Libido can be negatively affected by certain medications, abnormally low testosterone levels and by psychological and psychiatric conditions.
Achieving and maintaining an erection requires increased blood flow into small blood vessels in the penis. There is a concurrent relaxation, or closing off, of other blood vessels so that the blood accumulated in the penis does not leak back into the vascular system, thus maintaining the erection.
Erectile dysfunction (an inability to obtain or keep an erection) occurs either because blood can not flow into the small vessels of the penis, or because the penis does not stay full of blood (for example, due to damage to the vessels from cardiovascular disease, high blood pressure, or diabetes, or due to spinal injuries, the side effects of certain medications, or smoking). Sometimes there are psychological factors – relationship, work and/or life stressors – that can lead to the development of erectile dysfunction. Additionally, normal testosterone levels are essential to having and maintaining an erection.
Erectile dysfunction occurs, to some degree, in over 50% middle aged to older men (Kasper, et al, 2015). Erectile dysfunction and premature ejaculation (ejaculating soon after sexual activity starts or more quickly than desired) are the most common problems men experience with sexual function.
Testosterone, Zinc and Sexual Dysfunction
Testosterone is one of the hormones necessary for male sexual development and sexual function. Unusually low levels of testosterone adversely affect male sexual function in every phase of the sexual response cycle. Low levels of testosterone may cause a decrease in sex drive and/or erectile dysfunction. Low testosterone levels may also negatively impact control of orgasm (ejaculation) and may impair a man's ability to produce sperm, thereby resulting in infertility.
Foods that are rich in zinc include oysters, crab, lobster, fortified breakfast cereals, pumpkin seeds, dark chocolate and egg yolks. Adequate dietary zinc contributes to normal testosterone levels and to normal male and female fertility and reproduction, yet zinc deficiency is wide-spread, even in resource-rich countries. Deficiency is most commonly caused by malnutrition, alcoholism, a body's inability to absorb zinc, and/or chronic kidney diseases. Use of certain drugs, such as diuretics, can also lead to zinc deficiency. Lower than normal zinc levels are associated with lower levels of several hormones, including testosterone.
The 1996 publication of a study testing the relationship between zinc levels and testosterone levels demonstrated that inducing zinc deficiency in younger men lowered their testosterone levels, while supplementing with zinc in older men, who were already zinc deficient, increased testosterone levels (Prasad, 1996). Correlating zinc and testosterone levels was the endpoint of the study. The study did not go on to correlate normal testosterone levels with improved (or impaired) sexual function.
A later study, published in 2008, did correlate testosterone levels with sexual function. The study looked the levels of testosterone in men age 25 to 70. The significant finding was that abnormal testosterone levels affected men's control over ejaculation, and were more likely to cause either premature ejaculation or delayed ejaculation (Corona, 2008).
Pharmaceutical products have been developed and marketed to improve both male and female sexual function. Long before these drugs were available, various cultures employed different plants to enhance sexual function. Research is underway to identify the active components of some of these plants, and determine if and how they might work to address low interest in sex and/or issues related to erectile dysfunction and lack of control over ejaculation.
These plants include:
- Fadogia agrestis – has been studied in male rats and is linked an increase in sexual behavior which is assumed to be related to measured increases in testosterone.
- Panax ginseng – has shown promise in the treatment of erectile dysfunction as it contains a substance that helps prevent leakage of blood from the tissue of the penis.
- Ginkgo biloba - studies have demonstrated that ginkgo may have a positive effect on health conditions (such as cardiovascular disease) that increase the risk of erectile dysfunction; its effect of improving sexual health may therefore be secondary to the improvement of overall health.
- Myristica fragrans (nutmeg) – has been studied in female rats resulting in an apparent increase in sex drive.
- Epimedium sp. (known commonly as horny goats weed) – has been studied in combination products; Epimedium sp. has pre-established effects on hormonal regulation, depression, and heart and vascular disease any or all of which may explain its benefits on sexual health.
Greater attention to the sexuality of an ageing population has prompted an explosion of research and information to address issues of sexual function in both men and women. In response to the population demand for complimentary and alternative therapies, and the marketing of supplements promising to enhance sexual performance more and more research is being conducted.
Naturally, overall health is important for a healthy sex life. Supplementing diet with vitamins and minerals (especially zinc, folic acid and biotin), as well as some of the above listed herbal remedies may provide a boost in sexual function necessary to enhance the sexual experience.
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- Basson, R. (2001). Female sexual response: the role of drugs in the management of sexual dysfunction. Obstetrics & Gynecology, 98(2), 350-353. doi:10.1016/s0029-7844(01)01452-1
- Cai, T., Verze, P., Massenio, P., Tiscione, D., Malossini, G., Cormio, L., Mirone, V. (2016). Rhodiola rosea, folic acid, zinc and biotin (EndEP) is able to improve ejaculatory control in patients affected by lifelong premature ejaculation: Results from a phase I-II study. Experimental and Therapeutic Medicine. doi:10.3892/etm.2016.3595
- Corona, G., Jannini, E.A., Mannucci, E., Fisher, A.D., Lotti, F., Petrone, L., Maggi, M. (2008). Different Testosterone Levels Are Associated with Ejaculatory Dysfunction. The Journal of Sexual Medicine, 5(8), 1991-1998. doi:10.1111/j.1743-6109.2008.00803.x
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- Yan, W., Yu, N., Yin, T., Zou, Y., & Yang, J. (2014). A new potential risk factor in patients with erectile dysfunction and premature ejaculation: folate deficiency. Asian Journal of Andrology, 16(6):902-6.