Effects of dietary fibre extracts on calcium absorption in the rat

The effects on calcium absorption of several fibre extracts (which differed greatly in their chemical compositions, phytate concentrations, and proportions of soluble and insoluble fibre) and of phytate, as sodium phytate, were investigated in rats. Samples of fibre from apple, orange, pea, sugarbeet, barley and wheat were obtained from Sofalia (France). Calcium absorption (using a 47Ca tracer method) in 9-week-old rats from a purified diet, containing fibre at a level of 50 g/kg, was reduced by wheat and wheat-TDF fibre preparations and was unaffected by apple, orange, pea, sugarbeet, barley, pectin and guar gum, compared to the cellulose-containing diet. Calcium absorption was also reduced by increasing phytate concentration in the range 0 to 30 mmol/kg diet. Overall, the results suggest that calcium absorption is not affected by fibre components per se, (i.e. indigestible polysaccharides) and that the reduction in calcium absorption observed with wheat and wheat-TDF fibres is due to their phytate contents.