It is often said that beautiful people are solar powered, and this increase in summertime attractiveness has now been confirmed by research that found that ultraviolet light enhances sexual desire in humans. Presenting their findings in the journal Cell Reports, the study authors reveal that exposure to the sun increases “romantic passion” in both men and women, and identify a skin protein called p53 that regulates the connection between sunshine and horniness.
“It has been known for many years now that ultraviolet radiation from sunlight increases testosterone levels in males, and we also know that sunlight plays a major role in both the behavioral and hormonal regulation of sexuality,” explained study author Professor Carmit Levy in a statement. “However, the mechanism responsible for this regulation remained unknown. Our study enabled a better understanding of this mechanism.”
The researchers began by measuring the change in circulating sex-steroid hormones in mice that were exposed to light wavelengths within the ultraviolet B (UVB) range, such as those that typically cause suntan in humans. This resulted in a marked increase in key sex hormones, leading to a surge in sexual activity.
For instance, a rise in hypothalamus-pituitary-gonadal axis hormone caused female mice to develop larger ovaries and spend an extended number of days in the heat, while both males and females became more willing to engage in sexual intercourse following UVB exposure.
To determine whether or not this effect is mediated by receptors in the skin, the researchers repeated the experiment using mice that had been genetically engineered to lack a skin protein called p53. Normally, this protein responds to UVB radiation by triggering pigmentation and DNA repair in order to protect cells from the harmful effects of the sun’s rays.
Mice that lacked p53 showed none of the sexual responses to UVB that regular mice did, indicating that this protein is somehow responsible for converting sunlight into horniness.
Finally, the study authors treated 32 people with UVB phototherapy before administering questionnaires in order to gauge changes in sexual desire. Both males and females reported increases in romantic passion, with men also experiencing a spike in aggression.
“Passion takes two forms, emotional and sexual,” write the researchers, before going on to explain that UVB light appeared to trigger different aspects of romantic passion in the two genders. In women, for instance, exposure to sunlight seems to enhance elements of “physical arousal that related more to sexual passion and idealizing the connection [with a partner]”. In contrast, the “cognitive dimension of passion” became heightened in men, leading to “obsessive thoughts about the partner and wanting to know more about her.”
To confirm these effects, the researchers asked their subjects to avoid sunlight for two days before tanning themselves for 25 minutes. Blood tests then revealed that testosterone levels were considerably higher in all participants immediately after this sunning session than they had been 24 hours previously.
This indicates that exposure to sunlight triggers a rapid increase in sex hormone levels, and the researchers say that such a discovery could lead to the development of new light-based treatments for sexual dysfunction.