B Faraji | PubMed Health

PubMed1977

Binding of zinc and iron to wheat bread, wheat bran, and their components.

Wholemeal wheat bread decreases the availability and intestinal absorption of divalent metals. To define this action further, binding of zinc in vitro to a wheat wholemeal bread (Tanok), dephytinized Tanok, and cellulose was determined at pH 5.0 to 7.5. Zinc binding by each was highly pH-dependent and reached a maximum at pH 6.5 to 7.5. Removal of phytate from Tanok did not reduce its binding capability. Wheat bran at pH 6.5 and 6.8 bound 72% of iron (0.5 microgram/ml of solution) and 82.5% of zinc (1.43 microgram/ml solution), respectively. Lignin and two of the hemicellulose fractions of wheat bran and high binding capabilities for zinc (85.6, 87.1, and 82.1%, respectively) whereas a third had a lower zinc-binding capability (38.7%). Binding of zinc to various celluloses and dextrans is also demonstrated. Formation of complexes of these metals with wheat fiber can explain, at least in part, the decreased availability of dietary iron and zinc in wholemeal wheat bread.

Bread↗

PubMed1977

Effects of cellulose added to diets of low and high fiber content upon the metabolism of calcium, magnesium, zinc and phosphorus by man.

Addition of 10 g of cellulose dispersed in 150 g of apple compote to the daily diet with a low fiber content for a 20-day period caused the fecal excretion of calcium and zinc of three men to increase significantly. Balances of both metals became negative and their concentrations in plasma decreased. Magnesium balances became negative in two subjects while phosphorus balance changed to negative in one. In a similar experiment in which the cellulose was added to a fiber-rich diet, fecal excretions of calcium and zinc increased significantly in each of two men and excretion of magnesium in one. Previously negative balances became more negative, and calcium and zinc concentrations decreased in plasma. The dependence of fecal dry weight upon fecal fiber content measured by the acid-detergent method was confirmed. However, increments of dry matter per g of fiber were less fecal fiber concentrations were high. Fecal calcium content correlated significantly with fecal fiber in two subjects, and fecal fiber and zinc in one. No correlations were demonstrated in the subject who apparently digested fiber most effectively. Our findings indicate that high intakes of fiber can explain to a considerable extent the impaired utilization of zinc, calcium, and magnesium among villagers in rural Iran.

Adult↗