Prebiotic effects on calcium absorption and bone metabolism
Abstract
Adolescence is a critical time for reaching peak bone mass to prevent the risk of osteoporosis later in life. Dietary fibers and non-digestible oligosaccharides (NDO) are being investigated as a means to improve mineral metabolism and bone health through their unique interactions with colonic microflora. Bacteria residing in the colon are able to ferment ingested NDO thereby altering the luminal environment of the colon, which has been associated with increased absorption of calcium. The purpose of this body of work was to determine the effects of galactooligosaccharide (GOS) and soluble corn fiber (SCF) on calcium absorption and retention in adolescent children. To study the effects of GOS, a randomized, double-blind, placebo-controlled cross-over design was used to assess the effects of daily consumption of 0, 5, and 10 g GOS on calcium absorption in 10–12 year old, premenarcheal girls. GOS was provided in milk-based smoothies twice daily and consumed for 3 weeks. Calcium absorption tests were performed at the end of each 3-week period during a 2-day clinical visit. During this time, the girls consumed controlled diets with 1300 mg calcium per day, and all urine and fecal samples were collected for 48 hours after dual stable-isotope administration. Fractional calcium absorption was calculated based on urinary calcium isotope excretion and expressed as a ratio of excess 44Ca and 43Ca. GOS had a moderately positive effect on fractional calcium absorption (p=0.0132) with the 5 g treatment having the greatest impact on calcium absorption (Control=0.39 ± 0.10, 5 g GOS=0.43 ± 0.10, 10 g GOS=0.40 ± 0.13). Bifidobacteria composition was also significantly increased with GOS consumption when compared to baseline measurements before intervention. Overall, results from this investigation suggest that a modest intake of GOS is effective at increasing fractional calcium absorption in young girls. Soluble corn fiber effects on calcium absorption were evaluated during two, 3-week metabolic balance sessions of a randomized, placebo-controlled, crossover study in adolescent girls and boys, aged 12–15 years. The effects of 0 and 12 g/d SCF on calcium absorption and balance were studied under the condition of a controlled diet containing 600 mg daily calcium. Diet composites, fecal and urine samples were collected daily and analyzed for calcium content. Fractional calcium absorption was calculated as the ratio of excess 44Ca and 43Ca in the urine after accounting for natural abundance and administered doses. Pairwise comparisons revealed a significant difference in fractional calcium absorption at 48 h with SCF treatment increasing absorption by 12% compared to control (0.664 ± 0.129 and 0.595 ± 0.142, respectively; p=0.0239). SCF treatment had no effect on calcium balance. In summary, results from this study suggest that the addition of 12 g/d SCF has positive effects on calcium absorption in adolescent children with calcium intakes below daily recommended levels. Overall, results from these investigations support that prebiotics have a broad application in adolescent children. Using a variety of NDO products it may be possible to influence calcium absorption in both boys and girls on a range of calcium intakes. The moderate levels of prebiotics used in these studies increased calcium absorption in children ranging from 10 to 15 years of age indicating that if consumed at such achievable levels, they may positively impact the development of peak bone mass.
Degree
Ph.D.
Advisors
Weaver, Purdue University.
Subject Area
Nutrition
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