The pineal gland secretes melatonin. It is a circadian rhythm hormone – thereby affecting the patterns of sleep. Research has shown that the cells of the body rejuvenate and repair during the deeper stages of sleep. It is during the deeper stages of sleep that the body produces natural killer cells or CD4 cells. It also increases the deep stage of sleep and stage IV sleep, thereby increasing and enhancing immunity. Improved sleep patterns serve to energize the body and improve mood. Melatonin has powerful antioxidant effects which account for disease prevention qualities as well as having tremendous cancer prevention effects due to its enhancement of the immune system. A deficiency of this hormone results in poor sleep quality, jet lag, irritability, hypersensitivity and premature aging.