Researchers at Tel Aviv University have found that exposure to ultraviolet radiation from sunlight enhances romantic passion in humans. In the study, men and women were exposed to UVB (ultraviolet radiation type B) under controlled conditions and the findings were unequivocal: there were increased levels of romantic passion in both genders. The study showed exposure to sunlight affects the regulation of the endocrine system, responsible for the release of sexual hormones in humans.
The study was led by Ph.D. student Roma Parikh and Aschar Sorek from the laboratory of Prof. Carmit Levy at TAU's Department of Human Molecular Genetics and Biochemistry in the Sackler Faculty of Medicine.
In the animal models, female hormone levels rose significantly, enlarging their ovaries and prolonging their rut season; the attraction between males and females increased and both were more willing to engage in sexual intercourse.
In the 32 human subjects at the Tel Aviv Sourasky (Ichilov) and Assuta Medical Centers, both genders demonstrated a rise in romantic passion, and males also noted an increase in levels of aggression.
Similar results were found when they were asked to avoid sunlight for two days, then tan themselves for around 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 in the summer months was also found in data from the HMOs Clalit and Maccabi.
In the future, this may lead to treatments for sexual hormone disorders, as well as further development in scientific understanding of how sunlight plays a role in human psychological and behavioral processes.
"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 behavioral processes," Prof. Levy says. "It's only the tip of the iceberg."