It makes you hot, it makes you sweat, it gives off vitamin D and… it makes men hungry. A study in the journal Nature Metabolism unveiled by The Guardian shows that the sun generates unexpected effects.
In males, sun exposure may release ghrelin, a hormone that causes hunger pangs. Carmit Levy, a professor in the Department of Human Molecular Genetics at Tel Aviv University, and her colleagues conducted a nationwide nutrition survey of 3,000 participants. They found that the men ingested 300 extra calories a day during the summer. It’s not much, but it could be enough to cause weight gain. However, the same finding was not observed in women.
To further their research, the scientists exposed volunteers of both sexes to the sun for twenty-five minutes. Result: the level of ghrelin, also called “appetite hormone”, increased in men but not in women. Ghrelin is secreted more when the DNA present in certain tissues of the skin deteriorates in contact with the sun. Estrogens, hormones specific to female metabolism, could block this undesirable effect.
Ghrelin is convenient
According to Professor Levy, ghrelin has other effects on the body. It reduces inflammation and wasting of the heart muscle, and lowers blood pressure. “Ghrelin may be the mechanical link between sun exposure and reduced cardiovascular disease”she explains.
The sun would then help protect us from these diseases and other causes of death. Its light releases nitric oxides through the skin, causing blood vessels to relax and lowering blood pressure.
The fact remains that some doctors such as Duane Mellor, dietitian and lecturer at Aston University, remain cautious about the interpretation of these results. “This article does not claim that sun exposure will cause weight gain in men. It provides insight into the role of the hormone ghrelin in reducing cardiovascular risk and inflammation.”he nuances.