KENYA – Researchers have found that exposure to more sunlight over the summer triggers men to eat more.
In new findings the researchers said their study of data obtained from an Israeli health survey was aimed at looking into the ways that sunlight can lead to skin cancer in mice when they noticed that the male mice seemed to grow hungrier when exposed to UV light.
After this caught their attention, they say they wondered if the same might be true with humans, which is why they obtained data from a governmental questionnaire sent to people all across Israel enquiring about a host of health and nutritional issues.
They analysed the data from Israel’s three-year National Health and Nutritional Survey, which included 3,000 participants between the ages of 25 to 65 and by looking at the season, food intake and self-reported sex, they found that men increased their consumption by 17 per cent during the warmer months of March through September relative to the rest of the year, while women’s caloric consumption remained the same.
They further explain that one possible explanation for that finding is that there are sex-based differences in how sun exposure affects appetite. To verify this, the researchers asked a group of 13 men and 14 women between the ages of 18 to 55 to spend 25 minutes in the sun.
The group was then asked questions about their appetites.
The men reported feeling hungrier while women experienced no significant differences in their hunger levels before and after sun exposure.
The researchers collected participants’ blood samples before and after the exposure and found that circulating levels of ghrelin, a hormone that stimulates appetite, were elevated in men after they spent time in the sun. The experts went ahead to examine the hormone ghrelin—commonly known as the hunger hormone.
“Prior research has shown it is produced by cells in the stomach, and sometimes in the pancreas, small intestine and brain. It is transported through the bloodstream, activating neurons in the hypothalamus, which reacts by creating the sensations of hunger,” they said.
“The hormone has also been found to impact other brain regions such as the amygdala, which can stimulate the production of dopamine. Ghrelin levels are known to rise both during periods of hunger and just before a meal is consumed.”
In the lab, testing on mice showed ghrelin levels rising in male mice exposed to UVB radiation while secretion of the hormone was also discovered in skin samples obtained by male human volunteers who were exposed to UV light. “In females, estrogen interferes with the p53–chromatin interaction on the ghrelin promoter, thus blocking ghrelin and food-seeking behaviour in response to UVB exposure.”
In the past, scientists have observed that exposure to sunlight provides humans with benefits such as instigating the production of vitamin D and disadvantages such as skin damage as well as a higher risk of skin cancer.
