The effect of different levels of wheat bran on iron absorption in rats from bread containing similar amounts of phytate

Abstract

1. Iron absorption was studied in weanling rats using balance techniques from semi-synthetic diets containing dried white bread (60·5 g dietary fibre/kg, White & Southgate, unpublished results), brown bread (130·2 g dietary fibre/kg) or wholemeal bread (221·2 g dietary fibre/kg) at a level of 300 g/kg and compared with a control group given a diet containing added FeSO4 at a similar Fe level to that for the bread groups. The dried bread contained 6·2–6·4 g phytate/kg.2. Absorption of Fe was significantly higher (P < 0·001) in the control group (0·45) than in the white (0·28), brown (0·31) or wholemeal (0·24) groups.3. A second experiment was carried out on 6-week-old rats in which the dried bread was extrinsically labelled with 59Fe and absorption from a single meal measured by both faecal excretion and incorporation of 59Fe into the blood. Control animals were given 59FeSO4 for comparison.4. The excretion of 59Fe (% of administered dose) was significantly lower (P < 0·001) in the control group (31) than in the white (48), brown (45) or wholemeal (47) groups. After 10 d the control group had significantly more 59Fe in the blood than the bread groups, but there were no differences between the bread groups.5. It appears that wheat bran fibre itself has no effect on the retention of Fe from the diet in the rat, when supplied in amounts similar to those found in commercially-available bread.