THE EFFECT OF 6'-GALACTOOLIGOSACCHARIDES ON BONE MINERALIZATION OF RATS ADAPTED TO DIFFERENT LEVELS OF DIETARY CALCIUM

6'-galactooligosaccharides (6'-GOS), a mixture of galactosyl oligosacc harides formed from lactose by the trans galactosyl reaction with beta -D-galactosidase derived from Aspergillus oryzae and Streptococcus the rmophillus, are unhydrolyzed in the small intestine and are fermented by the intestinal bacteria. The effects of 6'-GOS on calcium (Ca) abso rption and bone mineralization were examined in male Wistar rats adapt ed to different levels of dietary Ca for 30 days. Dietary 6'-GOS (5 g/ 100 g of diet) were more potent control in stimulating Ca absorption i n rats fed the Normal-Ca diet (0.5 g of Ca/100 g of diet) after 8-10 d ays and 18-20 days, and the bone (femur and tibia) Ca content of rats fed the Normal-Ca diet with 6'-GOS were significantly higher than thos e of the control animals. However, in rats fed the Low-Ca diet (0.05 g of Ca/100 g of diet). 6'-GOS feeding did not affect both the absorpti on of Ca and the bone mineralization. Ca content in the liquid phase o f the cecal digesta was significantly elevated bo 6'-GOS feeding in th e rats fed the Normal-Ca diet, however, this was unchanged in the rats fed the Low-Ca diet. We conclude that the effect of 6'-GOS on the bon e mineralization is affected by dietary Ca concentration used in the e xperiment, and the stimulatory effect of 6'-GOS on Ca absorption may b e partly associated with increased solubility of Ca in the intestinal digesta.