INVIRO STUDY OF SOME FACTORS AFFECTING ZINC BIOAVAILABILITY

Document Type : Original Article

Authors

1 Faculty of Science, Ain Shams University, Cairo, Egypt

2 Institute of Environmental Studies and Researches, Ain Shams University, Cairo, Egypt

3 Central Lab. For Food and Feed, Agricultural Research Center, Giza, Egypt

Abstract

Five subjected groups of 5-weeks-old Swiss Webster out bred male mice were caged individually in stainless steel cages and maintained at 22-24° C and 45-55% relative humidity. The analysis of the previously prepared 5- different diets were done after complete homogenization of their ingredients. Mice group (A) were fed zinc deficiency diet adlibitum of "9.6 mg Zn / kg diet, mice group (8) were fed zinc controlled adlibitum diet "31.3 mg Zn / kg diet", mice group (C) were fed zinc supplemented adlibitum diet "60mg Zn /kg diet", zinc source of last groups is ZnS04.7H20. On the other hand, mice groups (D) and (E) were fed zinc supplemented adlibitum diet included phytic acid in concentration of 1497.0 and 1505.4 mg / kg diet respectively, as well as, their zinc sources are ZnS04.7H20 in concentration of 58 mg / kg diet in diet of mice group (D) and ZnNa2EDTA in concentration of "58.4 mg / kg diet" in diet of mice group (E). Experiments were initially designed to examine the simultaneous interaction between both zinc and other nutrient metals as calcium, iron and copper and the effect of dietary fiber of phytic acid on zinc absorption and study the impact of zinc absorption enhancement by using a chelating source of zinc as EDTA on the utilization of these nutrients. The duration of the experiment was 4- weeks divided into 2- intervals, 2- weeks for each interval. Serum calcium and iron were not affected by neither zinc deficiency nor zinc supplementation. Due to the aggressive competition between zinc and copper absorptions on the same cites of small intestine, copper absorption was positively highly affected by zinc deficient diet and recorded highly increasing in HDL- C "good cholesterol" and was negatively highly affected by zinc supplementation as hydrated zinc sulfate "ZnS04 .7H20" recorded high value of LDL- C "bad cholesterol". Zinc supplementation as "ZnNa2EDTA" recorded highly increasing in absorption levels of zinc and copper in blood. To the degree that affected the functions of kidney {urea and creatinine}. The majority of liver cells completely lost their cytoplasmic structure in mice of zinc deficient diet, either due to low intake of zinc or presence of dietary fiber of phytate. Phytate is known to form a complex with nutritional metals" Ca, Fe, Zn and Cu". Thus, the unavailable phytate and metallic nutrients complexed with it can not be utilized and were excreted. Hair analysis for minerals, gives a good and sensitive indication of actual metal levels while blood levels may still be in the normal range. Fortification the floor of the balady bread with zinc in EDTA form is a good intervention for the governorates which their villages suffere from signs and symptoms of zinc deficiency.

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