Scientists in Brazil have reported that supplementing the diet with the soluble dietary fibers - inulin and fructo-oligosaccharides (FOS), boosted calcium absorption in rats by about 40 percent, results that add to an ever growing body of science linking prebiotics with improved bone health.
The fibers - inulin and FOS - act as prebiotics to promote the growth of beneficial intestinal microflora. But an increasing body of science is emerging linking prebotics to help control blood sugar levels, reduce cholesterol, and boost bone strength.
The research, published in the September 2006 journal Nutrition Research, reports that rats supplemented with an enriched form of inulin containing a specific distribution of different chain lengths of inulin and oligofructose - boosted calcium absorption by about 40 percent, and led to greater bone strength.
“These results indicate an important role of fructo-oligosaccharides in the maintenance of healthy bones,” wrote lead researcher Alexandre Lobo from the University of Sao Paulo.
The researchers divided 16 male Wistar rats into two groups and fed all rats a control diet containing 7.5 grams of calcium per kilogram of diet for 23 days. One group of eight rats were supplemented with five percent inulin and fructo-oligosaccharides (FOS).
At the end of the study, the researchers reported that calcium absorption in the FOS supplemented group increased by 44 percent, compared to the control diet group. The bone mineral density in the middle of the thigh bone (midshaft femur) was 0.02 grams per sq. cm greater for the supplemented group, compared to the control diet group. The biomechanical properties, measures of the strength of the bones, also increased significantly for the inulin, FOS-supplemented groups, the scientists reported.
No adverse effects were observed for the inulin FOS-supplemented groups, but some increase in the moisture content of the animals' faeces was recorded.
The FOS is thought to work by changing the flora in the colon, with the more slowly fermented inulin acting as a selective 'fuel' for this modified flora, which is kept metabolically active further in the intestines. This selective fermentation pattern results in the production of short chain fatty acids, which increase the acidity in the colon, improving the solubility of the calcium present. The calcium is then better absorbed into the body.
Human studies are increasing, with a significant number of studies into the role of prebiotics on improving bone health of adolescent girls. One such study reported that girls and boys aged between 9 and 12 supplemented with a mixture of oligofructose and long-chain inulin had an additional net accretion of calcium of 30 milligrams per day, compared to the controls who received a placebo.
Lobo AR. Fructooligosaccharides improve bone mass and biomechanical properties in rats. Nutr Res 2006 Sep; 26(8): 413-420.
American Journal of Clinical Nutrition, 2005, Vol. 82, pp. 471-476