Your body oscillates between an awake state and a sleeping state. The oscillation coincides with day and night. Oscillations of this type are also known as circadian rhythms.

The pineal gland is a light sensitive gland in the brain. The most important hormone secreted by the pineal gland is melatonin. Melatonin secretions play a key role in the human circadian rhythm, which, among many other things, regulates sleep.

Modern life in industrialized nations is moving more and more indoors. There is less exposure to daylight, and much less exposure to the brightest daylight. An indoor life leaves the body unadapted to bright sunlight, and prone to sunburns. This leads to a further increase in sun avoidance.

Unintended consequences of these behavioral changes are large decreases in vitamin D produced from sunshine, and unusual signals from the pineal gland. Pineal gland secretions are known to be involved in signaling mammals to changes in the season. Pineal gland secretions are likely to respond to the size of the difference between maximum daytime light intensity and darkness. This difference is maximized in the summer and minimized in the winter. Even though it may be a bit painful, exposing the eyes to the full force of summer daylight by looking up at clouds in the middle of the day, might produce signals for the pineal gland that are important for healthy sleep. Looking into the sky was a natural, unavoidable behavior for most human beings up until modern times. Sunglasses and light sensitive lenses are very recent inventions.

Sleep disorders have reached epidemic proportions. Both melatonin and vitamin D are known to play important roles in the sleep cycle. If you are having trouble sleeping, there’s much to gain and little to lose by dramatically increasing sun exposure.