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Zinc is one of the 24 classical micronutrients needed for survival. It can be found in various meat, egg, and legume products and is especially high in oysters. Zinc is known as an aphrodisiac and Testosterone Booster, although the former is anecdotal and the latter only applies to the deficient (directly).
Zinc is highly involved in many enzyme systems in the body. Keeping normal zinc levels helps with the maintenance of these enzyme systems and acts as a hormonal and immune system aid. In very high doses, zinc can act as an aromatase inhibitor and lower estrogen levels but is a potent oxidant; especially in the male prostate. It is also implicated in repair of the intestinal mucosa at similarily high levels.
Zinc is also lost in sweat, as are many minerals, making mineral supplementation almost a necessity for athletes underconsuming the nutrient through food.
Zinc has it's intestinal uptake hindered by the other divalent minerals calcium, Magnesium, and iron when all four together exceed their transporter's uptake limit (around 800mg or so). Consuming these minerals alongside each other below this threshold is fine.
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(Note: Divalent Mineral (Z.I.M.C) competition only occurs at high acute doses exceeding 800mg, combinations below this dose do not exhibit much competitive inhibition)
Caution should be taken when using zinc supplementation surpassing the Tolerable Upper Limit of Intake (TUL) of 40mg, and if possible alternate supplements with better toxicology profiles should be used for those purposes desired.Examine.com Medical Disclaimer
15mg is the dose used for sedentary populations who may be deficient in zinc (vegetarians/vegans, caloric restriction) and 30mg the more common dose catered to athletes who lose zinc in sweat.
Doses up to 100-150mg are used as a cheap and potent aromatase inhibitor and doses around 300mg have shown efficacy in treatment of some gut dysfunction. Doses at this level, however, are probably not safe for chronic health given the Tolerable Upper Limit of Intake (TUL) is 40mg.
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One of the more common micronutrient deficiencies in athletes, vegetarians/vegans, and those who sweat a ton. Not really a common deficiency otherwise.
Although theoretically it competes for absorption with Magnesium (which would be problematic given the ZMA formulation) if taken on an empty stomach there should be enough transporters for both minerals. Just don't take with calcium (as that micronutrient is much more abundant and, thus, can use up said transporters)
Zinc is one of the 24 essential vitamins and minerals, specifically a mineral. It is found in high levels in animal tissues and eggs, legumes, and fish; it is exceptionally high in shellfish such as oyster. It may also be fortified into cereal grains in developed countries.
Zinc's main role in the body is as a prosthetic group for several enzymes called metalloproteins, one of which is the Superoxide Dismustase enzyme; an endogenous anti-oxidant involving both zinc and copper. Zinc is also involved in regulating the immune system. A deficiency in zinc is related to delayed growth in youth and hypogonadism in adult males as well as general mental lethargy and skin abnormalities.
The RDA values for zinc are an Estimated Average Requirement (EAR) of 6.5mg for females, 8.5-10mg for pregnant or lactating females, and 12mg a day for men. The Recommended Daily Intake (RDI) values are 8mg for females, 10-12mg for pregnant or lactating females, and 14-15mg for males, and the Tolerable Upper intake Limit (TUL) is in the range of 35-40mg for adults of both genders (all numbers daily requirements).
Zinc is known as a mineral regulatory of testosterone levels, and body stores are positively correlated with testosterone levels.
Supplementation is not generally needed if one has a good zinc intake through the diet. Thus practises to increase zinc absorption or to decrease zinc excretion could be potentially useful.
At least one animal study has suggested that dysregulation occurs with intestinal zinc absorption during aging, and adequate dietary intake may in turn be metabolically insufficient due to poorer absorption.
A meta-analysis (Cochrane) of 15 trials including 1360 persons overall noted that zinc, in the form of lozenges (gluconate) or syrup (sulfate), was associated with less duration and severity of the common cold when taken within 24 hours of onset that, after a week, had an odds ratio of 0.45 (less than half the risk) and noted that prolonged (5 month) usage was assocaited with less occurrence of the common cold with an incidence rate ratio of 0.64; this study could not make conclusions on persons with worse baseline health (immunosuppression, chronic illness) and did note wide variability in the study populations assessed. In this study, side effects were only noted with zinc lozenges rather than syrup and were limited to nausea and altered perception of taste, which is similar to results seen with past reviews on the subject matter. The dose range of the studies used was variable, ranging from 30-160mg daily.
Supra-physiological levels of zinc have been noted to influence steroid metabolism. Zinc has been used as an aromatase inhibitor in doses of 100-150mg. It has been noted to reduce aromatization of testosterone (via aromatase) in the rat liver. In addition to aromatase, Zinc has also been noted as an inhibitor of 5-alpha reductase, which converts testosterone into dihydrotestosterone (DHT).
As stated earlier, zinc is a regulator of testosterone levels. Supplementation of zinc increases testosterone if one was deficient in zinc before yet does not necessarily increase testosterone above baseline levels. That being said, it can reduce the exercise-induced depression of testosterone and exert a protective effect during periods of intense exercise. This one study using Zinc supplementation in road cyclists with 2-3 hours of training daily for 5 days a week noted that 30mg Zinc Sulfate daily for 4 weeks on top of a Zinc sufficient (15mg) diet failed to be significantly better than placebo or Selenium at increasing total testosterone levels, although there was a small but significant increase in free testosterone levels relative to placebo but only when measured after exhaustive exercise; testosterone levels tended to increase after exhaustive exercise.
Zinc Citrate, at 50mg elemental Zinc (146mg) daily for 4 weeks is associated with a maintenance of Zinc status while placebo declines over time (told to maintain a low Zinc diet, estimated between 10-12mg).
Zinc Gluconate, at 50mg elemental Zinc (385mg), appears to be slightly more effective than Zinc Citrate (nonsignificant) and can increase serum and erythrocytic stores of Zinc in apparently healthy persons over a period of 4 weeks.
Zinc Picolinate (bound to picolinic acid, a metabolite of tryptophan), at 50mg elemental Zinc (144mg) in healthy persons appears to increase urinary and serum levels greater than placebo and the other two forms tested (Citrate, Gluconate).
Very high levels of zinc intake (330mg daily) has been implicated in alleviating leaky gut syndrome in those with Crohn's Disease. It can also prevent or alleviate damage to the intestinal mucosa and some to the liver done by alcohol and due to alcohol causing zinc depletion, can also provide therapeutic-like benefit in treating alcohol-induced damage to the gut and liver. Many of these effects were noted as dose dependent, but were seen at 3-5mg/kg bodyweight (an incredibly high dose).
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