Alterations in zinc absorption and salivary sediment zinc after a lacto-ovo-vegetarian diet
01 Aug 1980-The American Journal of Clinical Nutrition (American Society for Nutrition)-Vol. 33, Iss: 8, pp 1757-1766
TL;DR: The increased plasma response to a zinc load and decrease in salivary sediment zinc after a vegetarian diet indicate that this diet adversely affects zinc status.
Abstract: The effect of a lacto-ovo-vegetarian diet on plasma zinc tolerance tests and plasma and saliva zinc levels was measured in 12 nonvegetarian women. A diet meeting the Recommended Dietary Allowances for all nutrients, including zinc, was fed to the subjects for 22 days. Initial zinc status of subjects was determined by zinc analysis of their diet, hair, plasma, and saliva. Plasma response to an oral load of 50 mg Zn was determined in five subjects before and after the dietary period. Zinc levels of salivary sediment, which consisted primarily of epithelial cells, significantly decreased from initial values of 128 to final levels of 94 �tg/g. No significant differences were found in zinc levels of plasma or whole mixed saliva. Plasma response to initial zinc tolerance tests were inversely correlated (P < 0.05) to dietary protein levels. Significantly increased plasma zinc uptake and areas under zinc tolerance curves were found after consumption of vegetarian diets compared to diets containing meats. The increased plasma response to a zinc load and decrease in salivary sediment zinc after a vegetarian diet indicate that this diet adversely affects zinc status. Am. J. Clin. Nuir, 33: 1757-1766, 1980.
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TL;DR: Improved assessment methods are required to determine whether vegetarians are at risk of zinc deficiency, and elements such as copper appear to be adequately provided by vegetarian diets.
Abstract: Iron and zinc are currently the trace minerals of greatest concern when considering the nutritional value of vegetarian diets. With elimination of meat and increased intake of phytate-containing legumes and whole grains, the absorption of both iron and zinc is lower with vegetarian than with nonvegetarian, diets. The health consequences of lower iron and zinc bioavailability are not clear, especially in industrialized countries with abundant, varied food supplies, where nutrition and health research has generally supported recommendations to reduce meat and increase legume and whole-grain consumption. Although it is clear that vegetarians have lower iron stores, adverse health effects from lower iron and zinc absorption have not been demonstrated with varied vegetarian diets in developed countries, and moderately lower iron stores have even been hypothesized to reduce the risk of chronic diseases. Premenopausal women cannot easily achieve recommended iron intakes, as modified for vegetarians, with foods alone; however, the benefit of routine iron supplementation has not been demonstrated. It may be prudent to monitor the hemoglobin of vegetarian children and women of childbearing age. Improved assessment methods are required to determine whether vegetarians are at risk of zinc deficiency. In contrast with iron and zinc, elements such as copper appear to be adequately provided by vegetarian diets. Although the iron and zinc deficiencies commonly associated with plant-based diets in impoverished nations are not associated with vegetarian diets in wealthier countries, these nutrients warrant attention as nutritional assessment methods become more sensitive and plant-based diets receive greater emphasis.
545 citations
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TL;DR: The essentiality of zinc for humans was recognized in the early 1960s and it is believed that the growth effect of zinc is related to its effect on protein synthesis, and whether or not zinc is required for the metabolism of somatomedin needs to be investigated in the future.
Abstract: The essentiality of zinc for humans was recognized in the early 1960s. The causes of zinc deficiency include malnutrition, alcoholism, malabsorption, extensive burns, chronic debilitating disorders, chronic renal diseases, following uses of certain drugs such as penicillamine for Wilson's disease and diuretics in some cases, and genetic disorders such as acrodermatitis enteropathica and sickle cell disease. In pregnancy and during periods of growth the requirement of zinc is increased. The clinical manifestations in severe cases of zinc deficiency include bullous-pustular dermatitis, alopecia, diarrhea, emotional disorder, weight loss, intercurrent infections, hypogonadism in males; it is fatal if unrecognized and untreated. A moderate deficiency of zinc is characterized by growth retardation and delayed puberty in adolescents, hypogonadism in males, rough skin, poor appetite, mental lethargy, delayed wound healing, taste abnormalities, and abnormal dark adaptation. In mild cases of zinc deficiency in human subjects, we have observed oligospermia, slight weight loss, and hyperammonemia. Zinc is a growth factor. Its deficiency adversely affects growth in many animal species and humans. Inasmuch as zinc is needed for protein and DNA synthesis and for cell division, it is believed that the growth effect of zinc is related to its effect on protein synthesis. Whether or not zinc is required for the metabolism of somatomedin needs to be investigated in the future. Testicular functions are affected adversely as a result of zinc deficiency in both humans and experimental animals. This effect of zinc is at the end organ level; the hypothalamic-pituitary axis is intact in zinc-deficient subjects. Inasmuch as zinc is intimately involved in cell division, its deficiency may adversely affect testicular size and thus affect its functions. Zinc is required for the functions of several enzymes and whether or not it has an enzymatic role in steroidogenesis is not known at present. Thymopoeitin, a hormone needed for T-cell maturation, has also been shown to be zinc dependent. Zinc deficiency affects T-cell functions and chemotaxis adversely. Disorders of cell-mediated immune functions are commonly observed in patients with zinc deficiency. Zinc is beneficial for wound healing in zinc-deficient subjects. In certain zinc-deficient subjects, abnormal taste and abnormal dark adaptation have been noted to reverse with zinc supplementation.
218 citations
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TL;DR: Plasma and urinary zinc levels were highly correlated when urinary zinc was 150 micrograms/day or more, indicating that urinary zinc responds more rapidly than plasma zinc to dietary changes and may be useful for evaluating zinc nutriture.
Abstract: Six healthy young men participated in a confined zinc depletion-repletion study which lasted 10 to 11 wk. The depletion period varied from 4 to 9 wk during which the subjects consumed a semipurified formula diet supplying 0.28 mg zinc/day. During a 1-wk initial baseline period, 15.7 mg of zinc as ZnSO4 were fed; 6.0, 23.2, or 46.3 mg of zinc were given during a brief repletion period for three of the men. Plasma, whole blood, urinary, fecal, and seminal zinc decreased significantly by the end of the depletion period. Erythrocyte, saliva, and hair zinc did not change. Plasma and urinary zinc levels were highly correlated when urinary zinc was 150 micrograms/day or more. In five of six subjects a drop in urinary zinc to below 150 micrograms/day was noted before a decrease in plasma zinc to less than 70 micrograms/100 g, indicating that urinary zinc responds more rapidly than plasma zinc to dietary changes and may be useful for evaluating zinc nutriture. The endogenous zinc loss averaged 2.2 mg/day; addition of the loss occasioned by one seminal emission would bring the total to 2.8 mg/day.
183 citations
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TL;DR: The history and present situation of Iron and Copper, as well as other metals-related disorders, are reviewed in detail in a volume entitled “Installing and Explaining Iron Deficiency .”
Abstract: INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 VARIABLES INFLUENCIN G INTESTINAL SOLUBILITY OF TRACE ELEMENTS 175 Dietary Phytate, Calcium, and Trace Metals...... .. . . . . . . . . . . . .. . . . . . . .. . . . ... . . . . . . ..... . . 175 Absorption and Metabolism of Copper . . . .. . . . . . . . . . . . . . . ..... . . . . . . . . . . . . . . . . . . 177 IMBALANCES IN VOLVIN G IRON S UPPLY OR UTILI ZATION ... . . . . . . . . . . . . . . . . . . . . . 1 80 Zinc and the Metabolism of Iron and Copper ...... . . . . . . . . . . . . . . . . .... .. . . . . . . . . . . . . . . . . . . . 1 80 Effects of Iron Deficiency on Trace Metal Metabolism . . . . . . . . . . ...... . . ..... 1 8 1 Effects of a High Iron Status .. .. .. . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 83 Iron Metabolism in Deficiencies of Nickel and Lead . . . . . . . . . . . . . . ...... . . . . . . . . . . . . . . . . . . . 1 85 M ETAB OLIC RES PONSES TO M ULTIPLE DEFICIENCIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 85 Modified Responses to Zinc Deficiency 1 85 Interrelated Effects of Selenium, Copper, and Manganese Deficiencies . . . . . . .... . . . . . . 1 86 CONCLUSION . .. . . . . . . . . . ....... ... . . . . . . . . . . . .... ....... .. . . . . . . . . .. . . . . . . ... ...... . . . . . . . .. ..... . . . 187
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561 citations
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TL;DR: Dietary phytate significantly reduced the average daily accumulation and wholebody retention of iron, copper, manganese and Zn, whether or not the diet was supplemented with Zn and inhibited 65Zn absorption, possibly by inhibiting reabsorption of endogenous65Zn and thus promoting a more rapid loss from the body.
Abstract: 1. The inclusion of phytate (10 g/kg) in a purified diet containing zinc (15 mg/kg) fed to young male rats significantly reduced growth rate and food intake, and promoted a cyclic pattern of food intake characteristic of an uncomplicated Zn deficiency. The decreased growth rate could be accounted for by the reduced food consumption. 2. Rats maintained on a Zn-deficient diet (0.5 mg Zn/kg) were found to have a cyclic pattern of food intake and a very slight weight gain. The addition of phytate (10 g/kg) to the Zn-deficient diet promoted a net loss of mean body-weight. 3. Rats maintained on the Zn-supplemented diet containing phytate excreted significantly more Zn in their faeces than either pair-fed or ad lib.-fed control rats. Rats given the Zn-deficient diet supplemented with phytate excreted more Zn in their faeces than Zn-deficient control rats. 4. Dietary phytate significantly reduced the average daily accumulation (mug/d) and whole-body retention (relative to dietary intake) of iron, copper, manganese and Zn, whether or not the diet was supplemented with Zn. 5. The addition of phytate to the lumen fluid of ligated loops of rat duodenum maintained in situ significantly inhibited 65Zn absorption, compared with the control systems without added phytate. 6. Other studies using ligated duodenal and ileal loops indicated that Zn is secreted into the gut lumen and approximately one-third of this is normally reabsorbed. Recycling of endogenous Zn may be a significant process in the over-all body economy of this trace element. 7. The absorption of 65Zn added to the diet was significantly reduced by dietary phytate. Dietary phytate also reduced the biological half-life of body 65Zn from 61 to 211 h post-administration, possibly by inhibiting reabsorption of endogenous 65Zn and thus promoting a more rapid loss from the body.
304 citations
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TL;DR: An overall homeostatic mechanism is proposed where metallothionein synthesis is controlled at the transcriptional level by body zinc status and functions in uptake and storage of zinc in hepatocytes and in the intestinal mucosal cells.
Abstract: A parenterally administered zinc load was used as a model to investigate zinc homeostasis in rats. Serum zinc increased markedly then decreased following the zinc load. The decrease was concomitant with enhanced zinc uptake into hepatocyte cytosol and metallothionein synthesis. Actinomycin D administration inhibited zinc uptake into liver cytosol and metallothionein synthesis. Both mRNA and metallothionein synthesis appear to be necessary for hepatic zinc uptake. Intestinal 65 Zn absorption was decreased in zinc loaded rats but was near normal in rats treated with actinomycin D prior to the zinc load. Absorption was not correlated with the serum zinc content but was inversely related to mucosal metallothionein synthesis and directly related to a zinc chelate complex. An overall homeostatic mechanism is proposed where metallothionein synthesis is controlled at the transcriptional level by body zinc status. In the liver, metallothionein synthesis functions in uptake and storage of zinc in hepatocytes. In the intestinal mucosal cells this protein competes with the normal ligand involved in zinc absorption and thus regulates the amount of zinc available for transfer to the plasma.
276 citations
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TL;DR: During a 20 day period of high fiber consumption in the form of bread made partly from wheaten wholemeal, two men developed negative balances of calcium, magnesium, zinc and phosphorus due to increased fecal excretion of each element.
Abstract: During a 20 day period of high fiber consumption in the form of bread made partly from wheaten wholemeal, two men developed negative balances of calcium, magnesium, zinc and phosphorus due to increased fecal excretion of each element. The fecal losses correlated closely with fecal dry matter and phosphorus. Fecal dry matter, in turn, was directly proportional to fecal fiber excretion. Balances of nitrogen remained positive. Mineral elements were well-utilized by the same subjects during a 20-day period of white bread consumption.
263 citations
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TL;DR: Results indicated that MTN-Zn in both liver and intestinal mucosal cytosol responded rapidly to an altered dietary Zn level and that serum Zn was directly related to the appearance ofMTN, offering support for the involvement of MTN in zinc metabolism.
Abstract: Metallothionein (MTN), a low molecular weight cytoplasmic metalloprotein has previously been implicated in the metabolism of Zn. Experiments were conducted with rats to determine the effect of feeding varying levels of dietary Zn for short periods on the increase or decrease in MTN-bound Zn. The results indicated that MTN-Zn in both liver and intestinal mucosal cytosol responded rapidly to an altered dietary Zn level and that serum Zn was directly related to the appearance of MTN. 65Zn absorption also responded rapidly to a change in dietary Zn and was inversely correlated with intestinal mucosal MTN-Zn. Hepatic 65Zn uptake appeared to be directly correlated with liver MTN-Zn. A 24 hour fast increased MTN-Zn in rats fed two different levels of Zn except in those rats that were previously treated with actinomycin D. The antibiotic, which blocks DNA-dependent RNA synthesis, appeared to block Zn uptake from blood to the liver. These findings offer support for the involvement of MTN in zinc metabolism.
155 citations