Nondigestible oligosaccharides do not interfere with calcium and nonheme-iron absorption in young, healthy men.

The effect of inulin, fructooligosaccharides, and galactooligosaccharides on true intestinal absorption of iron and calcium was measured in men by using double stable-isotope techniques (oral Fe-57 and Ca-44 and intravenous Fe-58 and Ca-48). The incorporation of iron isotopes into erythrocytes and the urinary excretion of calcium isotopes was measured with an inductively coupled plasma mass spectrometer. Twelve healthy, nonanemic, male subjects aged 20-30 y received four treatments consisting of a constant basal diet supplemented with 15 g/d inulin, fructooligosaccharide, or galactooligosaccharide, or not supplemented (control treatment). These four treatments were given for 21 d each according to a randomized, crossover design. Iron absorption was measured over the last 7 d of treatment (days 15-21) and calcium absorption was measured on day 21 of each treatment period. Mean (+/- SEM) iron absorption was 5.5 +/- 1.6%, 6.1 +/- 1.9%, 5.3 +/- 1.9%, and 5.1 +/- 1.5%, respectively, during treatment with inulin, fructooligosaccharide, galactooligosaccharide, or the control; mean (+/- SEM) calcium absorption was 25.8 +/- 2.3%, 26.3 +/- 1.9%, 26.3 +/- 2.6%, and 28.1 +/- 4.3%, respectively. None of the differences between treatments was significant. It is concluded that 15 g/d inulin, fructooligosaccharide, or galactooligosaccharide did not have a negative effect on iron and calcium absorption in young healthy men.