Melatonin

June 29, 2008

MelatoninMelatonin is a hormone produced and secreted by the pineal gland. The pineal gland is a small gland located in the center of the brain. The pineal gland is only active during darkness, through stimulation from the central nervous system. The central nervous system activates it in order to stimulate production of melatonin. Increased melatonin causes the body to feel less alert; essentially this means that the body becomes relaxed for sleep. During sleep, melatonin has additional roles in fighting the damage caused by reactive oxygen species, and other harmful free radicals produced from normal cell metabolism. This protection offered from a normal melatonin balance slows aging and boosts immunity to disease reducing the risk of infectious diseases and most cancers.

Many athletes may suffer from sleep disorders, since they have such a hectic schedule with exercising and keeping in shape. These types of activities and stressful days can upset the balance of melatonin, leading to insomnia. Two factors are needed for the pineal gland to produce melatonin. It must be between 9 pm and 9 am and it must also be dark. At night, even indoor lighting can have sufficient brightness to inhibit the production of melatonin by the pineal gland. In one research study, scientists show that melatonin supplementation to rats subjected to an acute swimming exercise can reduce lactate levels. Lactate is produced as lactic acid builds up from the working muscles. A reduction in lactate levels delay exhaustion, suggesting that the right balance of melatonin reduces the accumulation of toxic substances that would otherwise harm the body during physical activity.

In other studies with adult men, the immediate effects of ingesting melatonin in the daytime included decreased alertness and body temperature. These investigators found that the effects of 5 mg of melatonin seem more pronounced for mental rather than physical components of short-term athletic performance, although the cardiovascular responses to exercise were affected. Some effects of melatonin were apparent 5 hours after ingestion when the increase in body temperature subsided. These results suggest that the use of melatonin can be beneficial if used to regulate an athlete’s sleep cycle. A night with melatonin can improve the athletes’ performance, since they will be well rested. A good night’s rest will help the body repair some of the damage generated during the extensive physical training exerted on the body.

The reduced blood flow followed by restored blood flow as often experienced in situations of intense physical exercise results in severe oxidative injury to tissues and organs. It has been documented that during these situations, the activities of several antioxidants and levels of some small antioxidants become elevated. Melatonin has been identified as one of these potent small antioxidant molecules that is often especially high levels during these changes in blood flow, including during animals’ arousal from hibernation or in newborns during delivery. Because high melatonin production is short lived just for this period, it is thought that it is not related to the normal melatonin rhythm. Instead this short lived melatonin peak probably protects from the destructive oxidation that occurs during these periods. It has also been recognized that these high levels of melatonin seem to be derived from several organs not just the pineal gland that usually produces melatonin. The high melatonin production present at arousal from hibernation or in the newborns at birth does not appear to be controlled by light. It occurs both during the day and at night equally. Therefore, melatonin plays an important role as an antioxidant to protect against oxidative stress due to changes in blood flow during intense physical exercise.

Melatonin, plus L-tryptophan, which can be converted to melatonin, both effectively protect the pancreas from damage due to overstimulation or blood flow changes. It has been suggested that the positive effects of both melatonin and L-tryptophan on the pancreas may be due to the activity of melatonin as an antioxidant.

Currently there are two types of melatonin supplements available without prescription: natural and synthetic or man-made. A small amount of melatonin can postpone or speed up the normal cycle of sleeping at night and waking in the day by as much as six hours. Several people taking melatonin have reported feeling better in general. It appears to have the ability to strengthen the immune system, the gastrointestinal tract, and retina of the eye as well as reduce the amount of harmful free radicals in the body. There are no common side effects of taking melatonin, even at higher doses. Rare side effects from melatonin can include increased blood pressure, exhaustion, sadness and infertility. Anyone with heart problems, hypertension or previous strokes probably should avoid melatonin. Due to the rare side effect of infertility, it should be avoided by women planning on having children. The good news is that the risk of melatonin toxicity or an overdose seems non-existent.

References:
Atkinson G, J. H. (2005). Effects of daytime ingestion of melatonin on short-term athletic performance. Ergonomics. , 48 (11-14), 1512-22.

Jaworek J, N.-P. K.-S. (2007). Melatonin as modulator of pancreatic enzyme secretion and pancreatoprotector. J Physiol Pharmacol. , 58 (6), 65-80.

Kaya O, G. K. (2006). Melatonin supplementation to rats subjected to acute swimming exercise: Its effect on plasma lactate levels and relation with zinc. 27 (1-2), 263-6.

Tan DX, M. L. (2005). Physiological ischemia/reperfusion phenomena and their relation to endogenous melatonin production: a hypothesis. Endocrine., 27 (2), 149-58.

Szczepanik, M. (2007). Melatonin and its influence on immune system. J Physiol Pharmacol., 58 (6), 115-24.

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