AgingPhase 2NCT06519877
Fiber and Calcium Absorption in Older Men
A Phase 2 study testing Soluble corn fiber in people with Aging, run by VA Office of Research and Development at 1 site in United States.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 60 years and older, men onlyHealthy volunteers can take part
- Conditions the study is for
- Aging
- What is being tested?
- Soluble corn fiber
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 30 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Jan 2025to 1 Jan 2029
- Phase
- Phase 2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 60 years and older
- Men only
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Male Veterans 60 years of age
Who cannot join
- 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
Show all 9Show fewer
- 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.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
San Francisco VA Medical Center, San Francisco, CA
San Francisco, California, 94121-1563
Karin C Wu, MD, 415-221-4810, karin.Wu@va.gov
Karin C Wu, MD
About this study
Official title: Modulation of the Gut Microbiome by Dietary Fiber to Improve Calcium Absorption and Bone Health in Older Men
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.
Read the detailed description
Osteoporosis and associated fractures are a major problem in older men. One in four men over the age of 60 will sustain an osteoporotic fracture during his lifetime. Moreover, the mortality rate in men after fractures is nearly twice that in women. Despite the burden of fractures, little is understood about the pathogenesis of progressive bone loss in men. Studies point to dietary fiber as a potentially important mitigator of decline in bone mass, likely through increased intestinal calcium absorption and retention, as studied in adolescents, young men, and postmenopausal women. However, the effects of dietary fiber in older men have not been tested and the mechanism by which dietary fiber influences calcium absorption is unclear. The gut microbiome, which is crucial for host nutrient metabolism and hormone modulation, is a likely but underexplored mechanism.
The overall objective is to examine the effects of soluble corn fiber on intestinal calcium absorption with modulation of the gut microbiome in older men. The central hypothesis is that soluble corn fiber augments production of short-chain fatty acids by the gut microbiome, which modulates the production of systemic insulin-like growth factor 1 to increase calcium absorption and bone mass.
This study is a crossover intervention study on the effects of soluble corn fiber vs. placebo on intestinal calcium absorption and gut microbiome composition and function in 30 older male Veterans 60 years of age. Participants will be randomized 1:1 to sequential soluble corn fiber 20g/day vs. placebo for4 weeks each with a 4-week washout period. Individualized doses of calcium and vitamin D supplementation will also be provided through out the study period. Study measurements at the end of each intervention include intestinal calcium absorption via a dual stable isotope method, detailed gut microbiome characterization with metagenomics and metabolomics, dietary assessment, calciotropic hormones, and bone turnover marker levels. Baseline bone density and microstructure will also be obtained.
- Conditions
- Aging
- Being tested
- Soluble corn fiber
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Soluble corn fiberDietary supplement
Soluble corn fiber, also referred to resistant maltodextrin, is a type of dietary fiber made from corn starch. Soluble corn fiber is typically used to thicken processed foods and has been marketed as a prebiotic to improve digestive health.
| Study group | Role | What they receive |
|---|---|---|
| Group 1 | Experimental | Soluble corn fiber 20g/day x 4 weeks, washout period for 4 weeks, and placebo (maltodextrin) x 4 weeks. Receives: Dietary Supplement: Soluble corn fiber |
| Group 2 | Experimental | Placebo (maltodextrin) 20g/day x 4 weeks, washout period for 4 weeks, and soluble corn fiber x 4 weeks. Receives: Dietary Supplement: Soluble corn fiber |
What is being measured
The primary outcome is the main question the study is designed to answer.
Intestinal fractional calcium absorption
Dual stable calcium isotopic tracer method
Measured: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Secondary outcomes (4)
Biochemical markers of bone turnover
Blood draw
Measured: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Calciotropic hormones
Blood draw
Measured: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Gut microbial profiling
Stool collection
Measured: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Adherence, tolerability, and acceptability
Questionnaire
Measured: Throughout study period, an average of 12 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted25 Jul 2024
- Study start1 Jan 2025
- Primary completion1 Jan 2029 (estimated)
- Study completion1 Jan 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for AgingStudies of the same condition, open and under way.
- More trials run by VA Office of Research and DevelopmentThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- Participants will be randomized into one of two groups at a 1:1 ratio in random permutated blocks of size 6. Each group will undergo 2 phases of intervention with soluble corn fiber 20g/day for 4 weeks and placebo (maltodextrin) for 4 weeks, with 4-weeks of washout in between. Group 1 will receive soluble corn fiber first followed by placebo, whereas group 2 will receive placebo first followed by soluble corn fiber. Outcomes will be assessed at the end of each intervention phase.
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 30 participants (estimated)
Sponsor and investigators
- Lead sponsor
- VA Office of Research and Development
- Sponsor type
- US federal agency
- Collaborators
- San Francisco VA Health Care System
- Responsible party
- Sponsor
- Investigators
- Karin C Wu, MD, Principal investigator, San Francisco VA Medical Center, San Francisco, CA
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06519877
- Sponsor's protocol ID
- ENDB-009-23F
- Other IDs
- 24-41270
- Status last verified
- Feb 2026
- First submitted
- 20 Jun 2024
- Last updated
- 17 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 17 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Modulation of the Gut Microbiome by Dietary Fiber to Improve Calcium Absorption and Bone Health in Older Men
- ClinicalTrials.gov ID
- NCT06519877
- Acronym / sponsor ID
- ENDB-009-23F
- Conditions
- Aging
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 30 participants (estimated)
- Lead sponsor
- VA Office of Research and DevelopmentUS federal agency
- Collaborators
- San Francisco VA Health Care System
- Study start
- 1 Jan 2025 (actual)
- Primary completion
- 1 Jan 2029 (estimated)
- Study completion
- 1 Jan 2029 (estimated)
- First posted
- 25 Jul 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
Osteoporosis and associated fractures are a major problem in older men. One in four men over the age of 60 will sustain an osteoporotic fracture during his lifetime. Moreover, the mortality rate in men after fractures is nearly twice that in women. Despite the burden of fractures, little is understood about the pathogenesis of progressive bone loss in men. Studies point to dietary fiber as a potentially important mitigator of decline in bone mass, likely through increased intestinal calcium absorption and retention, as studied in adolescents, young men, and postmenopausal women. However, the effects of dietary fiber in older men have not been tested and the mechanism by which dietary fiber influences calcium absorption is unclear. The gut microbiome, which is crucial for host nutrient metabolism and hormone modulation, is a likely but underexplored mechanism.
The overall objective is to examine the effects of soluble corn fiber on intestinal calcium absorption with modulation of the gut microbiome in older men. The central hypothesis is that soluble corn fiber augments production of short-chain fatty acids by the gut microbiome, which modulates the production of systemic insulin-like growth factor 1 to increase calcium absorption and bone mass.
This study is a crossover intervention study on the effects of soluble corn fiber vs. placebo on intestinal calcium absorption and gut microbiome composition and function in 30 older male Veterans 60 years of age. Participants will be randomized 1:1 to sequential soluble corn fiber 20g/day vs. placebo for4 weeks each with a 4-week washout period. Individualized doses of calcium and vitamin D supplementation will also be provided through out the study period. Study measurements at the end of each intervention include intestinal calcium absorption via a dual stable isotope method, detailed gut microbiome characterization with metagenomics and metabolomics, dietary assessment, calciotropic hormones, and bone turnover marker levels. Baseline bone density and microstructure will also be obtained.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- Participants will be randomized into one of two groups at a 1:1 ratio in random permutated blocks of size 6. Each group will undergo 2 phases of intervention with soluble corn fiber 20g/day for 4 weeks and placebo (maltodextrin) for 4 weeks, with 4-weeks of washout in between. Group 1 will receive soluble corn fiber first followed by placebo, whereas group 2 will receive placebo first followed by soluble corn fiber. Outcomes will be assessed at the end of each intervention phase.
| Arm | Type | Receives |
|---|---|---|
| Group 1 | Experimental | Dietary Supplement: Soluble corn fiberSoluble corn fiber 20g/day x 4 weeks, washout period for 4 weeks, and placebo (maltodextrin) x 4 weeks. |
| Group 2 | Experimental | Dietary Supplement: Soluble corn fiberPlacebo (maltodextrin) 20g/day x 4 weeks, washout period for 4 weeks, and soluble corn fiber x 4 weeks. |
Who may qualify
- Ages
- 60 years and older
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Male Veterans 60 years of age
Key exclusion criteria (9 listed)
- 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)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Soluble corn fiberSoluble corn fiber, also referred to resistant maltodextrin, is a type of dietary fiber made from corn starch. Soluble corn fiber is typically used to thicken processed foods and has been marketed as a prebiotic to improve digestive health. | Dietary supplement | Group 1, Group 2 |
Primary outcome
Intestinal fractional calcium absorption
Time frame: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Dual stable calcium isotopic tracer method
4 secondary outcomes
Biochemical markers of bone turnover
Time frame: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Calciotropic hormones
Time frame: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Gut microbial profiling
Time frame: At week 4 and week 12 of study participation (at the end of each treatment phase x2)
Adherence, tolerability, and acceptability
Time frame: Throughout study period, an average of 12 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 17 Feb 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Karin C Wu, MD principal investigator
San Francisco VA Medical Center, San Francisco, CA
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Soluble corn fiber in people with Aging, run by VA Office of Research and Development at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 17 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Karin C Wu, MD ((415) 221-4810, karin.Wu@va.gov), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Intestinal fractional calcium absorption (time frame: At week 4 and week 12 of study participation (at the end of each treatment phase x2)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 17 Feb 2026.