Another benefit of sunlight exposure is the regulation of melatonin.
Melatonin is responsible for a sleep-wake cycle or circadian rhythm (also known as natural body clock). The more melatonin you have, the better you sleep. Sunlight actually reduces melatonin, making you more awake. It is very good for the organism to wake up with the sunrise, a natural way to stay very active throughout the day as the circadian clock is reconciled with the sun cycle.