People need exposure to light because sunlight provides ultraviolet B (UBV) rays that help the body produce vitamin D. Vitamin D helps balance the calcium that the body needs in order to maintain healthy bones and teeth. The amount of sun exposure a person needs depends on the climate.
Sunlight and light generally also help prevent and treat depression and sadness in people of all ages. The brain begins producing the mood-influencing chemical called serotonin upon first exposure to light in the morning. To treat or prevent sadness or depression, increase the amount of light a person is exposed to during daytime hours.