The amount of zinc needed to meet normal daily recommended intakes will be different for different individuals. The latest recommendations for zinc intake are given in the new Dietary Reference Intakes developed by the Institute of Medicine. Dietary Reference Intakes (DRIs) is the umbrella term for a group of reference values used for planning and assessing nutrient intake for healthy people. The Recommended Dietary Allowance (RDA), one of the DRIs, is the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals. For infants 0 to 6 months, the DRI is in the form of an Adequate Intake, which is the mean intake of zinc in healthy, breastfed infants. The AI for zinc for infants from 0 through 6 months is 2.0 milligrams (mg) per day.
For oral dosage form (capsules, lozenges, tablets, extended-release tablets)
To prevent deficiency, the amount taken by mouth is based on normal daily recommended intakes (Note that the normal daily recommended intakes are expressed as an actual amount of zinc. The dosage form [e.g., zinc gluconate, zinc sulfate] has a different strength). Zinc gluconate is a popular form for the delivery of zinc as a dietary supplement.Zinc supplements are most effective if they are taken at least 1 hour before or 2 hours after meals. However, if zinc supplements cause stomach upset, they may be taken with a meal.
Because zinc is an essential part of nearly 300 different biochemical pathways, structure/function claims can be made for the nutrient’s role in a wide variety of processes including digestion, wound healing, energy production, growth, cellular repair, collagen synthesis, bone strength, cognitive function, carbohydrate metabolism (glucose utilization and insulin production), and reproductive function. Even mild zinc deficiency has been associated with depressed immunity, decreased sperm count and impaired memory. Perhaps the most popular claim for zinc lately is for its role in immunity, where zinc may interfere with the replication of the cold virus (rhinovirus).
Many researchers working in different areas of the world have found that zinc supplementation increases growth among stunted children and reduces the prevalence of common childhood infections, such as diarrhea and pneumonia.It was a sick child's refusal to swallow a pill that led to the discovery of one of zinc's most interesting applications as a cure for the common cold.The cold-fighting reputation of zinc has had its ups and downs. That's because many zinc studies — both those that find the mineral beneficial and those that do not — are flawed. In studies with positive results, zinc seemed most effective taken as a lozenge or nasal spray within 24 hours of the onset of symptoms. Taking zinc with food reduced side effects, including a bad taste and nausea.
Zinc deficiencies are associated with many serious health conditions such as prostate problems, diabetes, infertility (zinc is present at very high levels in seminal fluid), fatigue and poor wound healing. Also poor appetite ( a deficiency affects the sense of taste and smell), anorexia and bulimia, and high cholesterol.Mild to moderate zinc deficiency can lead to significant reductions in ability to take up and use oxygen, remove carbon dioxide and generate energy during high intensity exercise. Zinc has also been linked to enhanced bone formation and reduction of bone loss – both alone and in combination with plant isoflavones such as genistein. When used together with isoflavones, it appears that the isoflavonoid effect on bone is enhanced by zinc and may have a potent role in prevention of bone loss.
Occasionally, high dose zinc supplements are recommended to diabetic patients. Such patients commonly suffer from increased loss of zinc and reduced body stores of zinc. High doses of zinc have been shown to mimic the effects of insulin in reducing blood sugar and promoting wound healing. These effects, however, should be considered preliminary and high dose zinc supplements are not recommended for diabetics except on the advice of their personal physician. Exercise performance has also been associated with adequate zinc status – especially in athletes who avoid red meat, concentrate their diets too.
But,too much zinc supplementation may not be a good thing for the urinary system of older adults, according to a new report.
The finding comes from a secondary analysis of a trial involving 3,640 adults between age 55 and 80 years of age with the retinal disease, macular degeneration. As treatment for their eye condition, the subjects were assigned to various treatments: daily antioxidant therapy with vitamin C, vitamin E and beta-carotene; zinc, 80 milligrams daily; antioxidants and zinc in combination; or inactive 'placebo' supplements.
In the Journal of Urology, Dr. Aaron R. Johnson and colleagues from the University of Wisconsin, Madison, report that there was a "significant increase in hospital admissions due to genitourinary causes in patients on zinc vs. non-zinc formulations (11.1 percent vs. 7.6 percent)" during the 6 years of the study.
These increased admissions were largely due to an increased number of urinary tract infections and urinary stones.
Zinc had no effect on the likelihood of developing a cancer of the urinary system. In fact, "a protective effect for high dose zinc was not demonstrated for any aspect of the genitourinary system," Johnson and colleagues say.
These results, they conclude, "suggest that patients receiving high dose zinc supplementation without a clear health indication should use caution until further trials are performed."
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