The neurotransmitter serotonin, also known by its chemical name 5-hydoxytryptamine, is released by neurons in the pineal gland of the brain but can affect structures all over the body. Some of the effects of serotonin seem unrelated, making this compound one of the most diverse in the body. The amino acid tryptophan, found in foods such as turkey, milk and bananas, is the building block of serotonin. Exercise, adequate sleep and certain medications can all raise serotonin levels in the body.
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Mood and Mental Effects
Sometimes referred to as the happiness molecule, serotonin has a profound effect on mood. High levels of serotonin lead to a cheerful disposition and the ability to withstand everyday stress. Depression can result from chronically low serotonin levels. Other mental disorders linked to low serotonin include social anxiety, obsessive-compulsive disorder, anorexia, bulimia, phobias, bipolar disorder and body dysmorphic disorder.
According to the University of Bristol, 90 percent of serotonin travels to the gastrointestinal system of the body to affect the organs there. Held in the enterochromaffin cells lining the intestines and stomach, serotonin is released in response to food ingestion and works to control the contractions that push food through the digestive tract. Changes in serotonin levels may contribute to irritable bowel syndrome, or IBS. High serotonin levels in the gastrointestinal tract may cause diarrhea, while constipation is linked to low serotonin levels.
Sleep Cycle Control
Serotonin is important in regulating the sleep cycle, and levels of the compound rise and fall as the body shifts between sleep and wakefulness. Along with melatonin, serotonin controls circadian rhythms and is affected by sunlight. Serotonin is at its lowest levels during deep sleep and highest when fully awake during the daytime. It is also linked to dreaming and the ability to go back to sleep upon awakening in the night. This regulation of sleep and wakefulness by serotonin has been implicated as a potential factor in sudden infant death syndrome, or SIDS, which typically occurs in babies with low levels of the neurotransmitter.
Other Body Processes
Serotonin affects many other bodily processes, too. Breathing and heart rate can both be affected by serotonin. Serotonin is released during blood clotting and may help regulate the activity of clotting factors. The effect of serotonin on libido has also been studied and high levels may cause a decrease in sexual desire, a common side effect of antidepressant medications that raise levels of the neurotransmitter in the body. Serotonin also plays a role in regulating body temperature, maintaining proper pH levels of the blood and controlling the appetite.