Sunlight leads to more sex, study says

The ultraviolet radiation in sunlight can increase attraction and willingness to engage in intercourse, researchers say.

Dave Yasvinski 3 minute read August 26, 2021

Ultraviolet radiation (type B) contained in sunlight plays a role in the regulation of the endocrine system — the part of the body that controls the sexual hormones. Getty

Ultraviolet radiation has an arousing effect on adults that leads to the release of sexual hormones and enhances romantic passion, according to a new study that proves the best time to make hay really is when the sun is shining.

The research, published in the journal Cell Reports, found that ultraviolet radiation (type B) contained in sunlight plays a role in the regulation of the endocrine system — the part of the body that controls the sexual hormones of humans and other animals — and can increase attraction and willingness to engage in intercourse.

“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 Carmit Levy, one of the authors of the study at the department of human molecular genetics and biochemistry at the Sackler Faculty of Medicine. “However, the mechanism responsible for this regulation remained unknown.”

In the first stage of the experiment, researchers exposed animal models to UVB light at wavelengths between 320 and 400 nanometres and witnessed a significant increase in female hormone levels, an enlargement of ovaries and a prolonged mating season. Attraction levels between genders also increased dramatically, as did the desire have sexual intercourse.

In the second stage, researchers conducted the same experiment but only after removing a skin protein called p53 that identifies and repairs DNA damage by activating the skin pigmentation that guards against the sun’s rays. The removal of this protein negated the amorous effects UVB light previously had on the animal models, proving the sun’s radiation was the source of the hormonal and behavioural changes and that the skin’s protective system was also helping regulate sexuality.

The final stage of the study recruited 32 human subjects who completed several surveys on romantic passion and aggression before and after UVB exposure. Both genders exhibited elevated levels of romantic passion — with males also experiencing increased aggression — following exposure. Researchers were able to replicate these results by asking subjects to avoid the sun for two days before tanning themselves for 25 minutes. Blood tests confirmed higher levels of hormones, including testosterone, were present following exposure to the sun.

“The skin contains various mechanisms for dealing with radiation from sunlight and one of these is the p53 protein,” 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 team hopes their research will be built upon and put into practice, potentially leading to innovative new ways to treat disorders involving sexual hormones.

“Our findings open many scientific and philosophical questions,” Levy said. “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.”

Dave Yasvinski is a writer with