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Fiber and Calcium Absorption in Older Men

Modulation of the Gut Microbiome by Dietary Fiber to Improve Calcium Absorption and Bone Health in Older Men

Who can join

Ages 60 and older · Men · Healthy volunteers welcome

Inclusion Criteria:

* Male Veterans 60 years of age

Exclusion Criteria:

* History of malabsorption
* Hypercalcemia (corrected Ca \> 10.2 mg/dL)
* Vitamin D insufficiency (25OHD \< 30 ng/mL)
* Chronic kidney disease stage 3B or worse (CrCl \< 45 mL/min)
* Severe hypogonadism (AM fasting serum total testosterone \< 150 ng/dL)
* Daily use of proton pump inhibitor
* Use of medication(s) known to affect calcium metabolism
* Use of medications or supplements that could impact gut microbiota in the previous 3 months (antibiotics or commercially available probiotics or prebiotics.
* Presence of a condition or abnormality that in the opinion of the Investigator that would compromise the safety of the patient or the quality of the data.

About the study

Osteoporotic fractures are a major but underrecognized problem in men. There is growing evidence that low dietary fiber intake is a modifiable risk factor for age-related bone loss in men. Preclinical and human studies in adolescents and postmenopausal women suggest that dietary fiber intake influences bone metabolism by modulating the gut microbiome to augment intestinal calcium absorption, but it is unclear through what molecular mechanism and whether dietary fiber has the same effects in older men. In this crossover intervention study, the investigators will enroll and follow 30 older male Veterans to evaluate the effects of soluble corn fiber on intestinal calcium absorption and explore the contribution of the gut microbiome.

What is being tested

• Soluble corn fiber (dietary supplement)

Sponsor: VA Office of Research and Development · Participants: 30 · Started: Jan 1, 2025

Contact the study team

• Karin C Wu, MD · Phone: (415) 221-4810

Official record on ClinicalTrials.gov — NCT06519877

Locations in the U.S.

From ClinicalTrials.gov, data retrieved Oct 1, 2026. Each study sets its own eligibility; the study team decides who can join.