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Zinc has been used since ancient Egyptian times to enhance wound healing, although the usefulness of this approach is only partially confirmed by the clinical data of today. Zinc is necessary for the functioning of more than 300 different enzymes and plays a vital role in an enormous number of biological processes. Zinc is a cofactor for the antioxidant enzyme superoxide dismutase (SOD) and is in a number of enzymatic reactions involved in carbohydrate and protein metabolism. Its immune-enhancing activities include regulation of T lymphocytes, CD4, natural killer cells, and interleukin II. In addition, zinc has been claimed to possess antiviral activity. It has been shown to play a role in wound healing, especially following burns or surgical incisions. Zinc is necessary for the maturation of sperm and normal fetal development. It is involved in sensory perception (taste, smell, and vision) and controls the release of stored vitamin A from the liver. Within the endocrine system, zinc has been shown to regulate insulin activity and promote the conversion thyroid hormones thyroxine to triiodothyronine. Based on available scientific evidence, zinc may be effective in the treatment of (childhood) malnutrition, acne vulgaris, peptic ulcers, leg ulcers, infertility, Wilson's disease, herpes, and taste or smell disorders. Zinc has also gained popularity for its use in the prevention of the common cold. The role for zinc is controversial in some cases, as the results of published studies provide either contradictory information and/or the methodological quality of the studies does not allow for a confident conclusion regarding the role of zinc in those diseases.
Melatonin is a hormone produced in the brain by the pineal gland from the amino acid tryptophan. The synthesis and release of melatonin are stimulated by darkness and suppressed by light, suggesting the involvement of melatonin in circadian rhythm and regulation of diverse body functions. Levels of melatonin in the blood are highest prior to bedtime. Synthetic melatonin supplements have been used for a variety of medical conditions, most notably for disorders related to sleep. Melatonin possesses antioxidant activity, and many of its proposed therapeutic or preventive uses are based on this property. New drugs that block the effects of melatonin are in development, such as BMS-214778 or luzindole, and may have uses in various disorders.
Ginkgo biloba has been used medicinally for thousands of years. Today, it is one of the top selling herbs in the United States. Ginkgo is used for the treatment of numerous conditions, many of which are under scientific investigation. Available evidence demonstrates ginkgo's efficacy in the management of intermittent claudication, Alzheimer's/multi-infarct dementia, and "cerebral insufficiency" (a syndrome thought to be secondary to atherosclerotic disease, characterized by impaired concentration, confusion, decreased physical performance, fatigue, headache, dizziness, depression, and anxiety). Although not definitive, there is promising early evidence favoring the use of ginkgo for memory enhancement in healthy subjects, altitude (mountain) sickness, symptoms of premenstrual syndrome (PMS), and reduction of chemotherapy-induced end-organ vascular damage. Although still controversial, a recent large trial has shifted the evidence against the use of ginkgo for tinnitus. The herb is generally well tolerated, but due to multiple case reports of bleeding, should be used cautiously in patients on anticoagulant therapy, with known coagulopathy, or prior to some surgical or dental procedures.