Date of Award

Spring 2015

Degree Type


Degree Name

Master of Science (MS)


Food Science

First Advisor

Connie Weaver

Committee Chair

Connie Weaver

Committee Member 1

Cindy H Nakatsu

Committee Member 2

Bruce R Hamaker


Postmenopausal women are at greatest risk among healthy individuals of developing osteoporosis and associated fractures. Nondigestible, fermentable dietary carbohydrates have been shown to improve calcium absorption in adolescents and bone-strength parameters in the rat model. Of particular interest is soluble corn fiber (SCF), which improved rat bone strength the most in a survey of novel fibers, and improved calcium absorption by up to 13% in teen girls. Hypotheses about the mechanism behind this effect revolve around the production of short-chain fatty acids (SCFAs) in the large intestine during fermentation. The purpose of this work was to determine if SCF would also benefit postmenopausal women and to assess the effect on calcium absorption of a chronic increase in cecal concentrations of SCFAs in rats.^ To study the effect of SCF, a randomized, double-blind, placebo-controlled crossover design was used to assess the effects of daily consumption of 0, 10, and 20 g SCF on bone calcium retention in postmenopausal women. SCF was provided as PROMITOR® 85 SCF, which provides 85% fiber, and was consumed as a constituent of one muffin and one fruit-flavored drink daily for 50 days. To measure net bone calcium loss, participants' bones were labeled with 41Ca by administration of ≥50 nCi of 41Ca intravenously at least 100 d prior to the start of the study. Every 10 days, 24 h urine was collected, and 41Ca appearance was measured sensitively by Accelerator Mass Spectrometry, while total Ca was measured by ICP-MS. Urinary 41Ca:Ca from nonintervention periods was used to determine an expected rate of bone loss. A decrease in urinary41Ca:Ca from the expected amount during intervention periods reflected increased bone retention. A dose-response effect was demonstrated, with 10 g/d SCF and 20 g/d SCF improving bone calcium retention by 4.8% (P = 0.013) and 7% (0.007) respectively. Bone formation marker bone-specific alkaline phosphatase (BAP), and bone turnover markers osteocalcin (OC) and N-terminal telopeptide (NTx), were measured at the ends of the baseline period and each washout and intervention period. Of the biomarkers measured, the only statistically significant difference detected was measured in BAP, between placebo and 20 g/d SCF (8%, P = 0.035). Daily SCF consumption significantly increased bone retention in postmenopausal women. It is estimated that 20 g/d SCF would improve bone balance by 50 mg/d, or 2.5% total body BMC per year if the effect persists.^ To assess the effectiveness of SCFAs to increase calcium absorption, rats were chronically dosed in a randomized, placebo-controlled trial with SCFAs. Twice daily, the rats received 0, 300, or 600 umol SCFA conjugate base directly to their ceca through a cecal catheter. At the end of 11 days, 45Ca was administered to their ceca, and 45Ca appearance was measured in their plasma. No statistically significant difference was observed between treatments.^ These studies indicate that SCF, in achievable dietary intakes, is effective in supporting bone health in postmenopausal women, but also that increasing SCFA concentration in the large intestine may not be the only mechanism causing this benefit. It is possible that the protocol used to assess the effect of chronic SCFA dosing on calcium absorption is inadequate. New protocols should be considered, and other mechanisms, such as a shift in gut pH or microbial populations, should be assessed for their effects on calcium absorption.