Serotonin is a neurotransmitter associated with many physiological functions in the central nervous system. It is synthesized from l–tryptophan, an essential amino acid found in many protein foods. Deficient levels of serotonin in the brain can cause various medical conditions affecting mood, sleep, aggression, eating disorders, appetite and obesity.
Mood Disorders
According to psychiatric research scientists at McGill University, low serotonin levels can predispose subjects to mood disorders. The National Institute of Mental Health estimates that each year approximately 21 million American adults have a mood disorder such as major depressive disorder, dysthymic disorder and/or bipolar disorder. Mood disorders can be treated with anti-depressive drugs such as tricyclics, monoamine oxidase inhibitors and selective serotonin reuptake inhibitors that work by increasing or sustaining serotonin levels in the brain synapse.
Sleep Disorders
Serotonin plays a major role in regulating the sleep/wake cycle and is needed in the brain to induce and maintain sleep. Serotonin is a precursor in the production of melatonin, a hormone made in the brain that regulates circadian rhythm, a biological process of responding to and balancing daylight and darkness over a 24-hour cycle. Research scientists in the Netherlands and France have demonstrated that insomnia can be caused by desensitization of serotonin receptors in the brain and low nocturnal production of melatonin from serotonin, respectively.
Aggression
Psychologists at the University of Cambridge reported that serotonin plays a key role in regulating aggression. Their study demonstrates that people with manipulated lower serotonin levels were more aggressive. This observation helps to explain why some people become aggressive when hungry since serotonin is made from dietary intake of l-tryptophan.
Eating Disorders
Psychiatry research scientists at Beth Israel Hospital in Boston studied evidence for alterations in serotonin in patients with anorexia nervosa, bulimia and depression. They concluded that impairment of serotonin can cause concurrent or sequential periods of binge eating, behavioral impulsivity and depression in patients with these eating disorders. Mental Health America estimates that 85 percent of people with eating disorders are female, and that up to 3.7 percent and 4.2 percent of women suffer from anorexia or bulimia, respectively, at some point during their lifetime.
Appetite and Obesity
Richard Wurtman, M.D., and Judith Wurtman, Ph.D., at Massachusetts Institute of Technology, have studied the relationship between serotonin, appetite and obesity. They concluded decreased brain serotonin appears to be involved with disturbances in mood and appetite that affect overweight individuals who have cravings and excessive intake of carbohydrate-rich foods. A carbohydrate-rich, protein-poor meal stimulates l-tryptophan’s transport across the blood-brain barrier into the brain for the synthesis of serotonin. The brain utilizes food-induced changes in serotonin to affect the choice of what to eat at the next meal. Many people learn to over-eat carbohydrates to enhance their mood. This food-induced stimulation of serotonin production in the brain often causes weight gain.
References
- "Pharmacol Biochem Behav"; The role of serotonin...; Young, S.N., M. Leyton; Apr 2002
- "Prog Neurobiol"; Serotonin and sleep/wake cycle...; Portas, C.M., B. Bjorvatn; Jan 2000
- "Sleep"; Too little sleep...; Roman, V., I. Walstra.; Dec 2005
- "Am J Med"; Nocturnal 6-sulfatoxymelatonin excretion...; Leger, D., M. Laudon; Jan 2004
- "Biol Psychiatry"; Eating disorders and depression; Jimerson, D.C., M.D. Lesem; Sep 1990
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