Sunbathers may want to avoid midnight snacks before catching some rays.
A study in mice shows that eating at abnormal times disrupts the biological clock of the skin, including the daytime potency of an enzyme that protects against the sun's harmful ultraviolet radiation.
Although further research is needed, the finding indicates that people who eat late at night may be more vulnerable to sunburn and longer-term effects such as skin aging and skin cancer, said the senior author.
"This finding is surprising. I did not think the skin was paying attention to when we are eating," said the senior author.
The study showed that mice given food only during the day - an abnormal eating time for the otherwise nocturnal animals - sustained more skin damage when exposed to ultraviolet B (UVB) light during the day than during the night. This outcome occurred, at least in part, because an enzyme that repairs UV-damaged skin - xeroderma pigmentosum group A (XPA) - shifted its daily cycle to be less active in the day.
Mice that fed only during their usual evening times did not show altered XPA cycles and were less susceptible to daytime UV rays.
"It is likely that if you have a normal eating schedule, then you will be better protected from UV during the daytime," said the senior author. "If you have an abnormal eating schedule, that could cause a harmful shift in your skin clock, like it did in the mouse."
Previous studies have demonstrated strong roles for the body's circadian rhythms in skin biology. However, little had been understood about what controls the skin's daily clock.
The latest research published in Cell Reports documents the vital role of feeding times, a factor that scientists focused on because it had already been known to affect the daily cycles of metabolic organs such as the liver.
The study found that besides disrupting XPA cycles, changing eating schedules could affect the expression of about 10 percent of the skin's genes.
However, more research is needed to better understand the links between eating patterns and UV damage in people, particularly how XPA cycles are affected, said the co-lead.
"It's hard to translate these findings to humans at this point," said the co-lead. "But it's fascinating to me that the skin would be sensitive to the timing of food intake."
New research suggests that skin cancer cells are more likely to develop in mice with abnormal eating schedules, due to a disruption in the skin's biological clock.