Exposure to sunlight enhances romantic passion

Tel Aviv University researchers have found that exposure to ultraviolet radiation from sunlight enhances romantic passion, following a study in which men and women were exposed to UVB (ultraviolet radiation type B) under controlled conditions. The findings were unequivocal: increased levels of romantic passion in both genders.

In the study’s 32 human subjects, all treated with UVB phototherapy, both genders exhibited a rise in romantic passion, and males also noted an increase in levels of aggression. Similar results were found when the subjects were asked to avoid sunlight for two days, and then tan themselves for approximately 25 minutes. Blood tests revealed that exposure to sunlight resulted in a higher release of hormones like testosterone compared to one day before exposure. A rise in testosterone in males during the summer was also found in analyses of data from Israeli health maintenance organisations Clalit and Maccabi Health Services.

“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 behavioural and hormonal regulation of sexuality,” said Tel Aviv Professor Carmit Levy. “However, the mechanism responsible for this regulation remained unknown.”

The results of the study, published in the journal Cell Reports, reveal that exposure to sunlight affects the regulation of the endocrine system responsible for the release of sexual hormones in humans. In animal models, the effect was dramatic: the females’ hormone levels rose significantly, enlarging their ovaries and prolonging their mating season; the attraction between males and females increased; and both were more willing to engage in sexual intercourse.

The researchers repeated the experiment on the animal model, this time removing from the skin a protein called p53, which identifies DNA damage and activates pigmentation during exposure to sunlight as protection against its adverse effects. The removal of the protein eliminated the effect of UVB exposure on the animals’ sexual behaviour, convincing the researchers that exposure to radiation through the skin was the cause of the observed hormonal, physiological and behavioural changes, and that the protective system is also responsible for the regulation of sexuality.

“The skin contains various mechanisms for dealing with radiation from sunlight, and one of these is the p53 protein,” Prof Levy said. “We must remember that exposure to UV is dangerous, and can damage the DNA, as in the case of skin cancer. At the same time, two built-in programs in the skin, activated following exposure to sunlight, are in place to protect against DNA damage: the DNA repair system and pigmentation, namely the suntan, based on degree of exposure. By activating both systems, the p53 protein regulates the level of DNA damage. In our study, we found that the same system also activates the endocrine system of sexuality and potentially breeding.”

The discovery may lead to future practical applications, such as UVB treatments for sexual hormone disorders. It also opens up for further discoveries in basic science, with Prof Levy noting, “As humans, we have no fur, and our skin is thus directly exposed to sunlight. We are only beginning to understand what this exposure does to us, and the key roles it might play in various physiological and behavioural processes.

“It’s only the tip of the iceberg.”

Image credit: ©stock.adobe.com/au/Strelciuc

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