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Melatonin |
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| Melatonin is a hormone (N-acetyl-5 methoxytryptamine) produced especially at night in the pineal gland. The pineal is a key element in the maintenance of the body’s endocrine regulation (hormone balance), immune system integrity, and circadian rhythm (daily
metabolic balance).The pineal gland functions as a biological clock by secreting melatonin (along with many other neuropeptides) at night. The pineal gland serves as the timekeeper of the brain, helping to govern the sleep-wake cycle and, in animals, seasonal rhythms of migration, mating, and hibernation. Secretion of melatonin is stimulated by the dark and inhibited by light. The secretion of melatonin follows a daily rhythm governed by the body's master clock. Melatonin levels are low during the day. At sunset, the cessation of light triggers neural signals which stimulate the pineal gland to begin releasing melatonin.
Melatonin is synthesized from the amino acid tryptophan. Tryptophan (l-tryptophan) is an essential amino acid formed from proteins during digestion by the action of proteolytic enzymes. Tryptophan is converted to serotonin and finally converted to melatonin which is an indole. The tryptophan during the day is converted into serotonin, a brain chemical involved with mood. Serotonin, in turn, is converted into melatonin. Synthetic melatonin and melatonin derived from bovine pineal glands are available as over-the-counter dietary supplements. Melatonin occurs naturally in some foods but in fairly small amounts. Of all the plant-based foods, oats, sweet corn and rice are richest in melatonin, containing between 1,000 and 1,800 picograms of melatonin per gram. Ginger, tomatoes, bananas and barley have about 500 picograms per gram. In the human population, melatonin levels are highest in children. Healthy young and middle-aged adults usually secrete about 5 to 25 micrograms of melatonin each night. The amount of melatonin the body secretes tends to decline with age, a possible link with an age-related rise in difficulty sleeping. |
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Functions and health benefits of melatonin |
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| Melatonin is involved in synchronizing the body's hormone secretions, setting the brain's internal clock and generating circadian rhythms (daily biorhythms). Melatonin helps regulate sleep-wake or circadian rhythms. Normally, production of melatonin by the pineal gland is stimulated by darkness and inhibited by light. Melatonin can suppress libido by inhibiting secretion of luteinizing
hormone (LH) and follicle stimulating hormone (FSH) from the anterior pituitary gland. Among its key roles, melatonin controls the body's circadian rhythm, an internal 24-hour time-keeping system that plays an important role in when we fall asleep and when we wake up. The melatonin pulse regulates many neuroendocrine functions. When the timing or intensity of the melatonin peak is disrupted (as in aging, stress, jet-lag, or artificial jet-lag syndromes), many physiological and mental functions are adversely affected. The ability to think clearly, remember key facts, and make sound decisions can be profoundly hampered by these upsets in the biological clock. Melatonin is also one of the hormones that controls the timing and release of female reproductive hormones. As a result, melatonin helps determine when menstruation begins, the frequency and duration of menstrual cycles, and when menstruation ends (menopause).
In addition to its hormone actions, melatonin also has strong antioxidant properties and preliminary evidence suggests that it may help strengthen the immune system. Free radicals are chemical constituents that have an unpaired electron. The free radicals normally responsible for more than half of all free radical damage in the body (causing lipid peroxidation, DNA damage and protein oxidation). As an antioxidant, it hunts down and eliminates cell-damaging free radicals, possibly helping to prevent or delay the development of heart disease, cancer and other conditions. When combined with certain cancer drugs, it may destroy malignant cells. Melatonin is twice as effective at protecting cell membranes from lipid peroxidation as vitamin E. Melatonin is five times more effective than glutathione for neutralizing hydroxyl radicals. Melatonin and adenosine may be particularly important in protecting brain cells because glutathione concentrations are not very high in the brain. In addition to the hydroxyl radical, melatonin neutralizes superoxide, singlet oxygen, hydrogen peroxide and hypochlorous acid. Melatonin inhibits peroxynitrite formation by inhibition of the enzyme nitric oxide synthetase in some brain tissues. Melatonin increases gene expression and activity of the anti-oxidant enzymes glutathione peroxidase, superoxide dismutase and catalase. |
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Melatonin and sleep disturbances |
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Insomnia is a sleep disorder characterised by an inability to sleep and/or to remain asleep for a reasonable period during the night. Sufferers typically complain of being unable to close their eyes for more than a few minutes at a time, or of 'tossing and turning' through the night. Melatonin supplements help induce sleep in people with disrupted circadian rhythms and those with low melatonin levels.
Jet lag is a physical condition caused by crossing time zones during flight. The condition is generally believed to be the result of disruption to the circadian rhythms of the body. Shift workers and long distance travellers often find their circadian rhythm greatly disrupted. Recent research shows that melatonin is potentially effective in prevention and treatment of jet-lag. Melatonin taken in the evening will rapidly reset the biological clock and almost totally alleviate (or prevent) the symptoms of jet-lag. |
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Anti-aging, cancer, immunity and reproduction |
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Melatonin has the ability to enhance or augment the function of the immune system. It seems to be capable of neutralizing the negative effects that stress, drugs and infections have on the function of the immune system. Melatonin secretion naturally drops off with age. This decrease is so reliable that blood melatonin levels have been proposed as a measurement of biological age. Melatonin, along with vitamin C and E, is an antioxidant and prevents oxidative damage. Melatonin also appears to inhibit tumor growth. Melatonin may be of value in untreatable metastatic cancer patients, particularly in improving their quality of life. Several studies indicate that melatonin levels may be linked with breast cancer risk. Melatonin may enhance the effects of some chemotherapy drugs used to treat breast cancer. Administration of melatonin inhibits ovulation in humans by reducing luteinizing hormone concentrations. Melatonin supplements may benefit menopausal women by promoting and sustaining sleep. Melatonin levels may play a role in the symptoms of anorexia. Some interest has been shown in using melatonin in seasonal affective disorder (SAD), because the disorder is believed to be caused by the release of melatonin at an inappropriate time. |
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Dopamine and psychosis |
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| Disruption to the dopamine system has also been strongly linked to psychosis and schizophrenia. Dopamine moves into frontal lobe regulating flow of information coming in from other areas of the brain. Compromise in the flow of dopamine may cause disrupted or incoherent thought as in schizophrenia. Schizophrenia is most commonly characterized by both 'positive symptoms' (those additional to normal experience and behaviour) and 'negative symptoms' (the lack or decline in normal experience or behaviour). Positive symptoms are grouped under the umbrella term psychosis and typically include delusions, hallucinations, and thought disorder. Negative symptoms may include inappropriate emotional displays or flat emotional affect, poverty of speech, and lack of motivation. Certain drugs, such as cocaine, block the return of dopamine into the brain, resulting in a build up of dopamine in the synapse, leading to drug-induced psychosis or schizophrenia. |
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Contraindications, interactions, precautions, side effects |
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| Some people may experience vivid dreams or nightmares when they take melatonin. Melatonin can cause drowsiness if taken during the day. Individuals experiencing morning drowsiness after taking melatonin at night should take less of the supplement. Additional side effects that have been reported from melatonin include stomach cramps, dizziness, headache, irritability, decreased libido, breast enlargement in men (called gynecomastia), and decreased sperm count.
People should not drive or operate machinery when taking melatonin. Melatonin could interfere with fertility and also should not be taken by pregnant or nursing women. Use of melatonin by persons who already have an abundant supply of melatonin from their bodies, such as children, teenagers, and pregnant and lactating women can lead to overdose of melatonin. Melatonin taken with MAOI drugs can also lead to overdose because MAOIs inhibit the breakdown of melatonin by the body.
Melatonin should not be taken by people using certain antidepressants, such as Prozac (a serotonin inhibitor) or Nardil (a monoamine oxidase inhibitor). Interaction between melatonin and these types of antidepressants can cause a stroke or heart attack. Preliminary symptoms include confusion, sweating, shaking, fever, lack of coordination, elevated blood pressure, diarrhea, and convulsions. |
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Melatonin is a natural hormone produced in the pineal gland at the base of the brain. It plays a key role in the regulation of sleep and is believed to be important in maintaining the body��s normal circadian rhythm. Melatonin has been used for two primary reasons: sleep-related problems and jet lag. Click here for more information.