Copper zinc intake

Metallothioneins are a group of small proteins (about 6.5 kDa), found in the cytosol of cells, particularly of liver, kidney, and intestine. They have a high content of cysteine and can bind copper, zinc, cadmium, and mercury. The SH groups of cysteine are involved in binding the metals. Acute intake (eg, by injection) of copper and of certain other metals increases the amount (induction) of these proteins in tissues, as does administration of certain hormones or cytokines. These proteins may function to store the above metals in a nontoxic form and are involved in their overall metaboHsm in the body. Sequestration of copper also diminishes the amount of this metal available to generate free radicals. 

Mills, C.F. Zinc in Human Biology, Springer-Veriag, Inc., New York, NY, 1989, Milne, D.B., et al. Dietaiy Intakes of Copper, Zinc, and Manganese by Militaty Personnel, Fed. Proc., 37, 891 (Abstract) (1978). 

As with copper, zinc is an essential element for all plants and animals. It is necessary for the correct function of various enzyme systems. However, excessive intakes of zinc can have long-term effects as they can interfere with absorption of copper and iron in the diet, and may result in anaemia.39 JECFA has recommended a PTDI of 1 mg/kg bodyweight, equivalent to 60 mg/day for a 60 kg adult.38 In food, the major contributors to the diet are meat and its products, from which zinc is readily absorbed. Liver, with concentrations of around 62 mg/kg, contains the highest levels of any meat products, with other tissues having values of a half to a third of this figure. The second greatest source of zinc is cereals. Concentrations of zinc in whole cereal products are similar to those in meat. 

Taper et al. (13) investigated the effects of zinc intake on copper utilization in adult women. The experiment involved feeding three levels of zinc, ranging from 8.0 to 24.0 mg/day. Copper retention was not affected by zinc Intake. Urine losses of zinc were from 0.4 to 0.6 mg/day and fecal excretions paralleled the intake. Percent apparent absorptions of zinc were 7.75, 9.13, and 11.50 percent when intakes were 8.0, 16.0 and 24.0 mg/day. 

Three human metabolic studies have examined the effect of dietary zinc Intake on apparent copper absorption. Greger et al. (37) studied 11 adolescent girls, ranging in age from 12.5 to... 

The specific daily amounts of antioxidants and zinc used by the AREDS researchers were 500 mg vitamin C. 400 lU vitamin E, 15 mg beta-carotene (often labeled as equivalent to 25,000 lU vitamin A), 80 mg zinc as zinc oxide, and 2 mg copper as cupric oxide. Copper was added to thcAREDS formulations containing zinc to prevent copper deficiency anemia, a condition associated with high levels of zinc intake. (Retrieved March 28. 2007. from http //www.nei.nih.gOv/amd/summary.asp 2)... 

Oberlander, H.E. and K. Roth. 1978. The effect of heavy metal chromium, nickel, copper, zinc, cadmium, mercury and lead on the intake and deposition of calcium and phosphate in young barley plants. /. Plant Nutr. Manure, Soil Sci. 141 107-116. 

Goultate s sister volume to this book describes our intake of food in great detail and lists the bulk minerals such as sodium, potassium, magnesium, calcium, and phosphorus. The trace minerals are listed as iron, copper, zinc, selenium and iodine. Other trace minerals described as essential by inference from their occurrence in various enzymes in human and... 

One study showed that, in full-term infants, manganese is absorbed from breast milk and cow s milk formulas that were either unsupplemented or supplemented with iron, copper, zinc, and iodine (Domer et al. 1989). Manganese intake was greater in the formula-fed infants than in the breast-fed infants due to the higher manganese content of the formula. However, breast-fed infants retained more of their daily intake of... 

In contrast to its essentiality, every element of the periodic system may be toxic it is only a question of the intake quantities and the element specification. An intoxication can induce interactions with essential elements and induce deficiency symptoms well-known examples are the interactions of nickel with zinc, magnesium, and manganese (Anke etal. 19971), or cadmium with copper, zinc, and iron (Anke et al 1970). 

Animal foodstuffs supply two-thirds and more of the iodine, selenium, and zinc intakes (Table 4.14). Beverages contribute a relatively high share (10%) to iodine consumption, but only 5% to selenium and zinc intakes. The majority of the heavy metals (iron, nickel, molybdenum, copper, manganese) is provided by vegetable foodstuffs, and partly by beverages. Approxi-... 

Overexposure to zinc by food, water, and air commonly poses no risk to the general population. Long-term administration of zinc (100-150 mg per day) to patients to promote wound healing is usually well tolerated, but anemia may be induced in case of low copper status. This effect is readily reversible, however. Using a safety factor of 10 this means that an additional zinc intake of 10-15 mg per day does not constitute a health hazard (US ERA 1980). The provisional maximum tolerable daily intake for man has been estimated at 0.3 to 1.0 mg Znkg body weight (WHO 1983). 

No specific data regarding human subpopulations that are unusually susceptible to the toxic effects of zinc were iocated. Healthy elderly people have been shown to have greater daily zinc intake than housebound eiderly people (Bunker et al. 1987 Prasad 1988). Data from animal studies indicate that certain human subpopulations may be more susceptible to excess zinc because of zinc s depleting effect on copper (Underwood 1977). People who are malnourished or have a marginal copper status may be more susceptible to the effects of excessive zinc than people who are adequately nourished (Underwood 1977). 

Anemia has been observed in humans and animals after oral exposure to zinc. It has been postulated that excess zinc intake may result in copper deficiency (mechanisms of action are discussed in Section 2.3.5). The anemia observed following zinc intake is believed to be caused by the copper deficiency. Administration of copper has been shown to be effective in increasing the hemoglobin levels (Porter et al. 1977 Smith and Larson 1946). 

Festa MD, Anderson HL, Dowdy RP, et al. 1985. Effect of zinc intake on copper excretion and retention in men. Am J Clin Nutr 41 285-292. 

Fischer PWF, Campbell JS, Giroux A. 1991. Effects of low copper and high zinc intakes and related changes in Cu,Zn-superoxide dismutase activity on DMBA-induced mammary tumorigenesis. Biological Trace Element Research 30(1) 65-79. 

Sutomo FX, Woutersen RA, Vandenhamer CJA. 1992. Effects of elevated zinc intake on the copper metabolism and the pancreas of the mouse. Journal of Trace Elements and Electrolytes in Health and Disease 6(2) 75-80. 

Taper LJ, Hinners ML, Ritchey SJ. 1980. Effects of zinc intake on copper balance in adult females. Am J Clin Nutr 33 1077-1082. 

High levels of administered zinc limits copper uptake in humans and certain animals, and provides protection against toxicosis produced by copper in pigs and sheep. Excessive zinc in humans interferes with copper absorption from the intestine, resulting in copper deficiency, and eventually to cardiovascular diseases hi zinc intakes also decrease iron bioavailability, leading to a reduction of erythrocyte life span by 67%. Copper deficiency induced by excess dietary zinc is associated with lameness in horses, donkeys, and mules. 

Risk assessments are conducted under a far different set of guidelines. One of the first efforts to establish an upper limit for zinc intake was proposed by the Environmental Protection Agency (EPA) in the United States during their development of a reference dose for zinc. The reference dose, or RfD, is the level of substance intake that can be sustained for a lifetime without ill-effect. In setting an RfD the toxicologist tends to take a cautious approach. Copper and iron deficiency are known to be induced by high levels of zinc administration for example, a daily intake of 50 mg/day of supplemental zinc has been reported to produce modest inhibition of a red blood cell enzyme called superoxide dismutase. Whether or not this is a toxic effect remains a matter of conjecture to this day (8, 9). However, toxicologists, in the interest of public health, have tended to interpret this as a potentially adverse effect and 50 mg per day of supplemental zinc intake has become a point of reference for toxicity . 

Extrinsic labeling has been used in several studies to assess apparent copper absorption inhumans. This includes studies to evaluate apparent copper absorption from plant- and animal-based diets [263, 264], and also the effect of ascorbic acid [265], age [146, 266, 267], copper intake [267-271], zinc intake [146], and iron supplementation [272] on copper absorption. By measuring urinary excretion of the tracer, copper retention has also been assessed from vitamin B6-defident diets [271], in pregnant women [263], in young men consuming a low copper diet [268], and for high copper intakes [270]. 

The use of different sorbents for the removal of mycotoxins has been the subject of intense studies. Aflatoxins may be removed from milk, cream or peanut oil using hydrated calcium aluminosilicate clay or bentonite. These mineral materials are sometimes added directly to feed to immobilise mycotoxins in the digestive tract of livestock (reducing the transfer into the blood stream). For example, the addition of hydrated calcium aluminosilicate to the feed of dairy cows decreases excretion of aflatoxin Mj to milk by 24-44%. Experiments with the immobilisation of zearalenone have been promising. However, the question remains as to whether the use of these chemisorbents does not reduce the intake of some essential minerals (such as copper, zinc and iron) and water-soluble vitamins. 

Recent animal experiments have shown that a mild copper deficiency can result in elevated serum cholesterol levels, particularly in the presence of high zinc intakes, and... 

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