Obesity
Conditions
Keywords
gastric bypass, calcium absorption, postmenopausal women
Brief summary
Gastric bypass surgery is a highly effective treatment for obesity, but it has negative effects on skeletal health, due in part to a dramatic decline in intestinal calcium absorption capacity. Animal and human studies suggest that non-digestible fibers termed prebiotics, such as soluble corn fiber (SCF), augment calcium absorption in the lower intestine as they act as substrates for beneficial gut microbiota. This is a pilot randomized controlled trial of the effects of SCF vs. placebo on intestinal calcium absorption, bone turnover marker levels, and the gut microbiome in postmenopausal women who have previously undergone gastric bypass surgery.
Detailed description
The study is a pilot randomized control trial (RCT) of the effects of the prebiotic SCF vs. placebo in 20 postmenopausal women who underwent Roux-en-Y gastric bypass surgery 2-6 years previously and thus have completed the postoperative period of rapid weight loss and metabolic and dietary change. A 24 g/day dose of SCF85 (which is approximately 20 g/day fiber) will be tested, as that dose was proven effective for calcium absorption/retention in healthy postmenopausal women and adolescents. The SCF and the maltodextrin placebo will be mixed in water and consumed in divided doses twice daily for 2 months, a duration exceeding other SCF trials but remaining feasible for a pilot. The primary outcome will be change in intestinal calcium absorption, which is the efficacy outcome about which the study must collect preliminary data and from which the investigators must refine power calculations for the anticipated future trial. Because the investigators hypothesize that an increase in calcium absorption will decrease bone turnover and ultimately increase bone mineral density (BMD), the study will measure biochemical markers of bone turnover in this pilot. Secondary outcomes will be gastrointestinal tolerability and acceptability. On an exploratory basis, the study will determine effects of the prebiotic on the gut microbiome. This pilot will yield critical experience about feasibility of recruitment and adherence to the intervention and measurements.
Interventions
DIETARY_SUPPLEMENTPrebiotic: soluble corn fiber
prebiotic
DIETARY_SUPPLEMENTPlacebo: maltodextrin
placebo
Sponsors
University of California, San Francisco
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
San Francisco Veterans Affairs Medical Center
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
OTHER
Masking
QUADRUPLE (Subject, Caregiver, Investigator, Outcomes Assessor)
Intervention model description
Randomized, placebo-controlled pilot trial with a parallel-arm design
Eligibility
Sex/Gender
FEMALE
Age
18 Years to 75 Years
Healthy volunteers
No
Inclusion criteria
1. Postmenopausal women (no menses for ≥4 yrs) 2. ≤ 75 yrs old, 3. Underwent Roux-en-Y gastric bypass surgery for weight loss 2-6 years prior
Exclusion criteria
1. Serum 25(OH)vitamin D level \<30 ng/mL (to remove the effect of vitamin D insufficiency/deficiency)\* 2. History of \>1 bariatric surgical procedure 3. Antibiotic therapy in the last 3 months 4. Regular pre- or probiotic use in the last 3 months 5. Regain of \>50% of weight loss post-bypass 6. Calculated creatinine clearance \<30 mL/min 7. Serum calcium \>10.2 mg/dL 8. Use of hormone therapy, osteoporosis pharmacotherapy, glucocorticoids, or other medications impacting calcium metabolism 9. Thyroid stimulating hormone (TSH) \<0.01 milli-international units per liter (mIU/L) A potential participant may be excluded if she has a condition or abnormality that in the opinion of the Investigator would compromise the safety of the participant or the quality of the data. \*Women excluded due to 25(OH)D level will be offered re-screening after vitamin D supplementation.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in fractional intestinal calcium absorption | 2 months | Fractional calcium absorption to be determined using dual stable isotopic tracers |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Gastrointestinal tolerability | 2 months | Self-reported flatulence, bloating, abdominal pain, stomach noises |
| Change in bone turnover markers | 2 months | Serum biochemical markers of bone turnover C-telopeptide (CTX) and procollagen type 1 N-terminal propeptide (P1NP) |
| Acceptability | 2 months | Self-reported satisfaction, likelihood that one would be willing to consume the beverage for 12 months |
| Change in gut microbiome composition | 2 months | Stool bacterial and fungal composition to be analyzed, including alpha diversity and beta diversity metrics as well as taxon relative abundance, with subsequent in silico metagenomic predictions of enrichment of bacterial functional gene pathways |
Countries
United States
Outcome results
None listed