Absorption of zinc

Chisolm JJ Jr, Brown DH. 1979. Micromethod for zinc protoporphyrin in erythrocytes Including new data on the absorptivity of zinc protoporphyrin and new observation in neonates and sickle cell disease. Biochem Med 22 214-237. 

Renal tubular absorption of zinc in mice was impaired by certain diuretics and was further influenced by dietary proteins (Goyer 1986). Zinc absorption in rats was depressed after consumption of high levels of inorganic iron absorption was normal with organoirons (Greger 1989). 

No effect on apparent absorption of iron, manganese or copper although not statistically significant, absorption of zinc tended to decrease with increased phytic acid intake (44)... 

Dursun, N., and Aydogan, S. (1994). Comparative effects of calcium deficiency and supplements on the intestinal absorption of zinc in rats. Jpn. J. Physiol. 44,157-166. 

The Effect of Browned and Unbrowned Corn Products on Absorption of Zinc, Iron, and Copper in Humans... 

There are few data in the literature concerning zinc absorption from meals. However, King, et al. (18), also using stable tracers, reported 46% absorption of zinc from a formula meal by adult women who did not use oral contraceptives. Using 65Zn tracers, Sandstrom, et al. (19) reported 15.7% absorption from a meal containing white bread, milk, and cheese. 

Absorption of 65Zn Absorption of zinc from a 65Zn-labeled meal is given in Table IV and compared to measurements of zinc... 

Recently, it was shown using FT-IR that the decrease of vulcanisation rate and final crosslink density of sulfur vulcanised NR upon increasing silica content may be related to increased absorption of zinc stearate onto the silica surface [69]. 

Agren MS. Percutaneous absorption of zinc from zinc oxide applied topically to intact skin in man. Dermatologica 1990 180 36-9. 

The chemical balance technique is inadequate for the accurate assessment of dietary zinc availability and it does not permit, in any case, an evaluation of zinc availability from the separate components of a composite meal. Furthermore, although measurement of changes in the concentration of plasma zinc (3) following ingestion of pharmacological doses of the metal, has been used in studies of dietary zinc availability, this approach has not been validated with regard to its reliability and it cannot provide absolute data on the absorption of zinc. Indeed the only viable approach that can be followed is one Involving use of a suitable isotopic zinc tracer. 

Measurement of fecal zinc does not yield the value 0, but rather the total zinc excreted (of dietary and endogenous origin). Thus, determination of total zinc in the diet and the fecal pool will not provide an estimate of the absorption of zinc. However, if the isotopic makeup of the dietary zinc is suitably altered, via administration of a labeled diet, then isotopic analysis of the diet and of the corresponding fecal pool will satisfy the requirements of the above definition. For the simplest case where the natural isotopic composition of a single component of the diet has been altered (single-labeling) an estimate of the fractional absorption (F] ) of the mineral from the labeled diet component, can be made from two simultaneous equations, as follows (See Table I for definitions) ... 

Equation (4) above is the generally applicable expression for a singly labeled diet component when this component also contains a measurable level of isotope 2. For the case where the labeled component has been arranged so that its content of isotope 2 is negligible, as in the case of giving an oral dose of a highly enriched solution, as in the extrinsic tag approach, then Equation (5) is applicable. For situations where more than one component of the diet has been labeled by appropriate use of a selection of different stable isotopes, a more complex set of multiple simultaneous equations can be described (6) for determination of the absorption of zinc from the various labeled diet components. 

Comparative Data on Absorption of Zinc Measured with 65gn and Stable Isotope Methodology ... 

To explore the quantitative effect of various diet factors on the absorption of zinc from foods and diets, we have generally used an extrinsic tag of a stable isotope of zinc ( Zn). It is assumed that this tag mixes completely with the food Zn prior to its absorption and, thus, its absorption reflects the availability of zinc in the total diet (11, 16). The validity of this assumption needs to be further explored (O. Furthermore, we have been concerned with the question of the dietary availability of zinc when plant foods, such as various soybean preparations, serve as the major or sole source of protein Intake. For example, the results summarized in Table VI indicate that the absorption of an... 

A. E. Staley Manufacturing Co.). These results are given in Table VIII and they reveal that the level of absorption of zinc during the initial two weeks was maintained throughout a 3-month period with the constant diet. 

Finally, we have completed a study designed to evaluate and compare absorption of zinc from an "extrinsic tag" of ZnCl2 with that from an "intrinsic tag" given in the form of 68zn-labeled chicken meat ( ). These tracers were given simultaneously to young men studied during each of three experimental diet... 

Absorption of Zinc (/ Zn) from Diets Based on a Soy Isolate (Supro-620) or a Soy Concentrate (Stapro 3200) Given to Young Men (16)... 

These are the first studies of zinc absorption reported In a large group of normal subjects. Results of these studies are Important as a basis for comparison with data from patients with various diseases who may exhibit abnormalities of zinc absorption. Zinc absorption has been shown to decrease with age In normal humans, but whether this Is related to decreased anabolism with reduced demand for zinc or to some physiological or pathological process associated with aging Is unclear. The decreased absorption of zinc taken with food Is Important with respect to the design of studies of zinc metabolism. In the determination of zinc bloavallablllty and nutritional requirements of the trace metal and In treatment of subjects who may require zinc replacement. 

In order to deal with these complex problems all data from the oral Zn studies obtained in patients with taste and smell dysfunction were organized and submitted to compartmental analysis (68,69) with the subsequent development of a model (Figure 1) which accounted for all the data obtained over the entire period of these studies, both prior to and after treatment with exogenous zinc (69). These results, compared in normal volunteers, demonstrated that not only was absorption of zinc significantly impaired in the patients compared with the normal volunteers (Table IV) but also that the rate at which zinc was absorbed was significantly lower in the patients than in the normals (3j5 6 and that their total body level of zinc was lower than in the normals (6 6. By the use of this model it was also possible to specify those conditions which were both necessary and sufficient to identify patients with zinc deficiency (60.69). With these techniques it was possible to identify, by objective criteria, laboratory tests by which patients with subacute zinc deficiency could be defined quantitatively. It was also possible to measure various tissue and total body zinc levels and to compare patients with normals so that patients with zinc deficiency could be identified. The major problems presented with these techniques are that they are time consuming, cumbersome, expensive and are presently unavailable in many areas of the U.S. 

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. 

The molar ratio of phytate/zlnc of some mid-eastern diets was estimated to be 20 ( ), but only small amounts of meat were generally available. Sandstrom et al. obtained results that indicate absorption of zinc from a meal may be appreciably Influenced by the type of protein in the meal (, ). Our menus provided protein from meat in most of the meals which may have affected bioutilization of the dietary zinc. In one comparison Sandstrom et al. found that whole wheat bread decreased percentage absorption, but the absolute amount of zinc absorbed was greater because total zinc in the whole wheat bread meal was greater. 

Table VI. Tissue concentration and absorption of zinc in rats fed cookies ... 

Relative (zinc in cookie A=100%) biological value based on femur zinc content. Table VII. Tissue concentration and absorption of zinc in rats fed bread > ... 

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