I am a night owl — meaning midnight snack is a must. Various surveys showed that about 20-30% of the US population operates on a night owl schedule. If you are a night owl who plans to sunbath the next day, you might want to think again before reaching for that midnight snack bowl. A resent study by researchers from the UC Irvine suggest that eating at abnormal times disrupts the biological clock of the skin, which leads to the reduced ability of certain skin enzyme to protect us against the sun’s harmful UV radiation.
In the study, the mice were fed only during the day — an abnormal eating time for the otherwise nocturnal animals. The animals were exposed to UV radiation day and night. The result showed that the group sustained more UV-caused skin damage during the day than during the night. This means that the animals’ skin is more UV sensitive during the day, which should not be the case naturally.
Further investigation showed that this outcome occurred because an enzyme that repairs UV-damaged skin — xeroderma pigmentosum group A (XPA) — shifted its daily cycle to be less active in the day. The shift was caused by the abnormal feeding time. In comparison, mice that fed only during their usual evening times did not show altered XPA cycles and were better protected against daytime UV rays.
Although further research is needed, the finding suggests that eating late at night could cause a harmful shift in your skin clock and reduce skin’s ability to protect against UV radiation.
Human circadian rhythm (also known as sleep/wake cycle or body clock) is a natural, internal system that’s designed to regulate feelings of sleepiness and wakefulness over a 24-hour period. Previous researches have shown that eating schedules affect the circadian rhythm, which in turn affects liver functions and energy metabolism. For example, it is observed that the time of day food is eaten is more critical to weight loss than the amount of calories ingested. This study by UV Irvine researchers is the first one affirmatively linking the eating time, circadian rhythm and skin functions.
What’s the take home message? Eating late at night may make you more vulnerable to sunburn and consequently other detrimental longer-term effects such as skin aging and skin cancer. I know that I am going to skip that midnight ice cream today.
Thanks for reading.
Dr. Connie Wan
Journal Reference: Hong Wang, Elyse van Spyk, Qiang Liu, Mikhail Geyfman, Michael L. Salmans, Vivek Kumar, Alexander Ihler, Ning Li, Joseph S. Takahashi, Bogi Andersen. Time-Restricted Feeding Shifts the Skin Circadian Clock and Alters UVB-Induced DNA Damage. Cell Reports, 2017; 20 (5): 1061 DOI: 10.1016/j.celrep.2017.07.022