Prebiotic Inulin for Late-Reproductive Individuals (PILI)

July 20, 2026 updated by: Carmen Ortega-Santos, George Washington University

A Placebo Randomized Cross-Over Controlled Trial of Inulin Supplementation to Improve Cardiometabolic, Gut, and Vaginal Microbiome in Perimenopausal Women

This study aims to evaluate the effects of 2 weeks of inulin supplementation in perimenopausal women with overweight or obesity. The primary questions this study seeks to answer are:

  1. Does 2 weeks of inulin supplementation alter the gut and vaginal estrobolome compared with placebo?
  2. Does 2 weeks of inulin supplementation affect cardiovascular health compared with placebo?
  3. Does 2 weeks of inulin supplementation affect skeletal muscle health compared with placebo?

Researchers will compare inulin with a placebo (a similar-looking supplement that does not contain inulin) to determine whether inulin influences gut and vaginal microbial function, cardiovascular health, and skeletal muscle health during the perimenopausal transition.

Participants will:

  • Take either inulin or a placebo for 2 weeks, followed by a 2- to 4-week washout period, and then switch to the other supplement for an additional 2 weeks.
  • Attend 8 study visits over approximately 12 to 16 weeks for assessments and sample collection.
  • Complete weekly phone calls to monitor symptoms, supplement adherence, and dietary intake.
  • Wear a Fitbit device throughout the study to monitor physical activity.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This proposal presents a proof-of-concept study of the Prebiotic Inulin for Late Reproductive Individuals (PILI) intervention, a prebiotic fiber supplementation among women with perimenopause and overweight or obesity.

More specifically, the PILI intervention integrates multi-omics, physiological, and cardiometabolic assessments to examine the effects of inulin supplementation on overall health during the menopausal transition. Outcomes include changes in the gut and vaginal microbiome and their functional activity, gut-derived metabolites, vascular health, metabolic flexibility, skeletal muscle oxidative capacity, body composition, physical activity, sleep, dietary intake, and other cardiometabolic health markers. The target age range for this intervention is 40-55 years, reflecting the perimenopausal stage of life. Participants must also have overweight or obesity.

Participants will be randomly assigned to receive both the study intervention, inulin, and placebo, in a blind crossover design. Each participant will complete two intervention periods, separated by a washout period, allowing every participant to serve as her own control. Throughout the study, participants will consume the assigned supplement daily and attend scheduled in-person research visits before and after each intervention period.

At these visits, the research team will collect biological samples, including blood, stool, and vaginal swabs, and perform a comprehensive series of clinical assessments. These assessments include body composition, vascular health, metabolic flexibility, skeletal muscle oxidative capacity using near-infrared spectroscopy, physical function, and cardiometabolic testing. Participants will also complete questionnaires related to dietary intake, physical activity, sleep, menopausal symptoms, and quality of life, while wearing a Fitbit device to objectively monitor physical activity and sleep throughout the study.

The PILI study team will evaluate the feasibility of the intervention by assessing recruitment, retention, adherence to supplement consumption and study procedures, participant acceptability and tolerability, and completion of biological sample collection and clinical assessments. Preliminary changes in microbiome composition and function, microbial metabolites, and cardiometabolic health outcomes will also be evaluated to generate data that will inform the design of a future larger clinical trial.

This research has the potential to advance understanding of how prebiotic supplementation influences the gut-muscle-metabolism axis during the menopausal transition and to identify a safe, low-cost nutritional strategy to improve cardiometabolic health among perimenopausal women.

Study Type

Interventional

Enrollment (Estimated)

27

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Carmen Ortega-Santos, PhD, RD
  • Phone Number: 202-994-2757
  • Email: fitgutlab@gwu.edu

Study Locations

  • United States
    • District of Columbia
      • Washington D.C., District of Columbia, United States, 20052
        • Recruiting
        • Milken Institute School of Public Health
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Body mass index: 25 - 40 kg/m2;
  • Menstrual cycle irregularity (cycle length outside 21 - 35 days or variation > 7 days) or/and ≥ 2 skipped cycles and interval of ≥ 60 days of amenorrhea; with or without hot flashes or/and night sweats;
  • Weight stable within the last 3 months (body weight fluctuations within the 5% of their habitual body weight);
  • Spending ≥ 6 hours sitting;
  • < 150 minutes per week (50 minutes per day, 3 days per week OR 30 minutes per day, 5 days per week) of moderate to vigorous structured physical activity (i.e., planned intentional physical activity, not incidental movement).

Exclusion Criteria:

  • Recent antibiotic use oral or vaginal (≥ 6months);
  • Diagnosed with any chronic disease (e.g., any gastrointestinal condition like IBD, type 2 diabetes, or cancer);
  • Prescription of hormone replacement therapy, hormonal contraceptives, probiotics, GLP-1 medications, or weight loss medications
  • Smoking;
  • Recent blood donation (within the past 8-12 weeks);
  • Significant weight changes (≥5%) in the last 4 weeks;
  • Use of dietary supplements (unless discontinued 4 weeks prior);
  • Participants taking long-term, stable medications for chronic conditions such as hypertension or hyperlipidemia will not be excluded if their medication regimen has been unchanged for at least 2 years, as these treatments are part of their usual health status. Recent medication changes (within the past 6 months), initiation of new prescriptions, or use of medications known to affect metabolic, vascular, vaginal, hormonal, or gastrointestinal function will result in exclusion.
  • Fructose intolerance.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Sequence A (Inulin → Placebo)
Participants receive inulin daily for 2 weeks, followed by a 2-4 week washout period, then placebo for 2 weeks.
Dietary supplement: Inulin
10g per day for 2 weeks
Dietary supplement: Maltodextrin (Placebo)
10g per day for 2 weeks
Experimental: Arm 2: Sequence B (Placebo → Inulin)
Participants receive a placebo daily for 2 weeks, followed by a 2-4-week washout period, then inulin for 2 weeks.
Dietary supplement: Inulin
10g per day for 2 weeks
Dietary supplement: Maltodextrin (Placebo)
10g per day for 2 weeks

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in Gut Microbiome Composition
Time Frame: Baseline, end of each 2-week intervention period (inulin and placebo), and after washout period (2-4 weeks).
Change in gut microbiome composition, assessed by shotgun metagenomic sequencing, comparing inulin versus placebo in a randomized crossover design.
Baseline, end of each 2-week intervention period (inulin and placebo), and after washout period (2-4 weeks).
Change in Gut Microbiome Functional Capacity
Time Frame: Baseline, end of each 2-week intervention period (inulin and placebo), and after washout period (2-4 weeks).
Change in gut microbiome functional capacity, including biosynthetic gene clusters (BGCs) and estrobolome-related microbial pathways, assessed by shotgun metagenomic sequencing, comparing inulin versus placebo in a randomized crossover design.
Baseline, end of each 2-week intervention period (inulin and placebo), and after washout period (2-4 weeks).
Change in Vaginal Microbiome Composition
Time Frame: Baseline, end of each 2-week intervention period (inulin and placebo), and after washout period (2-4 weeks).
Change in vaginal microbiome composition, assessed by shotgun metagenomic sequencing, comparing inulin versus placebo in a randomized crossover design.
Baseline, end of each 2-week intervention period (inulin and placebo), and after washout period (2-4 weeks).

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Vascular Function
Time Frame: Baseline and end of each 2-week intervention period (inulin and placebo), with assessments conducted during each intervention period following the washout phase (2-4 weeks).
Change in vascular function, assessed by pulse-wave velocity (PWV), comparing inulin versus placebo in a randomized crossover design.
Baseline and end of each 2-week intervention period (inulin and placebo), with assessments conducted during each intervention period following the washout phase (2-4 weeks).
Metabolic Flexibility
Time Frame: Baseline and end of each 2-week intervention period (inulin and placebo), with assessments conducted during each intervention period following the washout phase (2-4 weeks).
Change in metabolic flexibility, assessed as the change in respiratory exchange ratio (RER) from the fasted resting state to the postprandial period following a standardized high-fat mixed meal, measured continuously via indirect calorimetry, comparing inulin versus placebo in a randomized crossover design.
Baseline and end of each 2-week intervention period (inulin and placebo), with assessments conducted during each intervention period following the washout phase (2-4 weeks).
Skeletal muscle mitochondrial oxidative capacity
Time Frame: Baseline and end of each 2-week intervention period (inulin and placebo), with assessments conducted during each intervention period following the washout phase (2-4 weeks)
Change in skeletal muscle mitochondrial oxidative capacity in the gastrocnemius muscle, comparing inulin versus placebo in a randomized crossover design. Muscle oxidative capacity will be assessed using near-infrared spectroscopy (NIRS).
Baseline and end of each 2-week intervention period (inulin and placebo), with assessments conducted during each intervention period following the washout phase (2-4 weeks)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

George Washington University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

July 1, 2026

Primary Completion (Estimated)

February 1, 2028

Study Completion (Estimated)

February 1, 2028

Study Registration Dates

First Submitted

July 15, 2026

First Submitted That Met QC Criteria

July 20, 2026

First Posted (Actual)

July 24, 2026

Study Record Updates

Last Update Posted (Actual)

July 24, 2026

Last Update Submitted That Met QC Criteria

July 20, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • NCR267325
  • 05RIA112025 (Other Grant/Funding Number: Milken Institute School of Public Health Research Innovation Award)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) will not be shared because the dataset contains sensitive health and behavioral information, and full de-identification and public release are not planned within the scope of this study.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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