The science of nutritional supplements is constantly evolving. Clinicians, researchers, industry and the government are trying to understand whether or not supplements have any clinical benefit or can play a role in everyday health. For now, use of these supplements must be based on existing data, which varies from substance to substance. Products such as creatine, melatonin, glucosamine, chondroitin sulfate, vitamins E and C, and chromium are among the most popular nutritional supplements, but despite their widespread use, questions over their safety and effectiveness remain.
Safety is also an issue.
Very little long-term safety data exist and there is some concern regarding its effects on the kidneys, particularly among those with compromised renal function. No drug, nutritional supplement or herb interactions have been noted thus far. Melatonin apparently can help one get a good night's sleep. In addition, there are promising findings that melatonin can be helpful in ameliorating sleep disturbances in totally blind people with free-running circadian rhythms. Claims have also been made that melatonin can favorably influence lipids, lower blood pressure, help prevent heart attacks, correct sexual dysfunction and enhance sexual performance.