EFFECT OF DIETARY FIBER LEVELS ON BIOAVAILABILITY OF SOME TRACE ELEMENTS (IRON AND ZINC) IN RATS
A.A. Afify1, F.A. El-Wakeil2, E.M. Hegazy1 and S.H. Abou Raya2
1National Research Center
2Faculty of Agriculture, Cairo University
The specific effects of different dietary fiber sources and raw potato starch (Resistant starch RS) on mineral utilization (Fe and Zn) were investigated in albino rats adapted to ad libitum semipurified diet for 4 weeks. Nine dietary diets including a control group, a broad bean group (10% total dietary fiber (TDF)), a soybean group (10% TDF), a potato starch group (8%TDF) as well as pan bread series of (five groups) with increasing amounts of dietary fiber (2, 4, 6, 8 and 10%TDF) by substituting wheat flour with 5, 10, 15 and 20% wheat bran were studied. Zinc and iron concentrations of the diets were adjusted to the level provided by the diet with the highest wheat bran content (pan bread diet containing 20% wheat bran (diet No. 8). Absorption and retention of Fe, Zn and plasma concentration of each of Fe and Zn were measured. Body weight gain and feed efficiency ratio (FER) for rats fed the on tested diets were followed up to the end of the experiment. Significant decreases in body weight gain and FER were noticed for rat groups fed on broad bean (10% TDF) and pan bread (10%TDF) diets, compared with the control group [(29.5, 28.0, 68.8 g/rat/28day) - (0.099, 0.095, 0.224)], respectively. The apparent absorption and retention of Fe and Zn were significantly reduced (P < 0.05) in the rats fed on the highest level of dietary fiber. Absorption rate was accompanied by increased fecal Fe and zinc contents and reduced the urinary Fe and Zinc levels. The results suggest that high levels of dietary fiber might inhibit iron and zinc absorption and retention and could result in iron, zinc deficiency in rats.