Probiotics on Immune Function and Intestinal Microbiota in Astronauts Under Closed Microgravity Environment

November 19, 2025 updated by: Yakult Honsha Co., LTD

Study for Evaluating the Impact of Continuous Consumption of Probiotics on Immune Function and Intestinal Microbiota in Astronauts Under Closed Microgravity Environment

Human immune function and intestinal microbiota are suggested to be altered within long-duration stay in space. Accumulated evidences on earth support that Lacticaseibacillus paracasei strain Shirota (LcS) is a promising probiotic strain on improvement of immune function and intestinal microbiota. This study aims to investigate the impact of long-duration spaceflight as well as intake of LcS on the international space station (ISS), on immune system and intestinal microbiota in astronauts.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

10

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 Locations

  • Japan
      • Ibaraki, Japan
        • Japan Aerospace Exploration Agency

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

25 years to 80 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Individuals who are scheduled to stay on the ISS for at least 3 months
  • Individuals who fully understand the study protocol and provide written informed consent for the study participation

Exclusion Criteria:

  • Individuals who routinely use antibiotic, laxative, and/or bowel regulating medicine
  • Individuals who participate in other research that competes with this study in terms of the purpose and field, e.g., study with dietary management or intake of bifidobacteria/lactic acid bacteria, oligosaccharides, antibiotic, laxative, and/or bowel regulating medicine

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: Basic Science
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
No Intervention: Control group
Experimental: LcS group
Consuming probiotic capsule
Dietary supplement: Probiotic capsule
Continuously take five capsules containing freeze-dried LcS on ISS for four weeks, from four weeks before the return (R-4W) to one day before the return (R-1d)

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Longitudinal changes in the number of LcS in feces
Time Frame: 9-18 months
Number of LcS in feces will be assessed by PMA-qPCR, during pre-flight, in-flight and post-flight.
9-18 months
Longitudinal changes in the level of immune markers
Time Frame: 9-18 months
Levels of immune markers in blood/saliva will be assessed by ELISA and bioassay, during pre-flight, in-flight and post-flight.
9-18 months
Longitudinal changes in numbers and composition of intestinal microbiota
Time Frame: 9-18 months
Numbers and composition of bacteria in feces will be assessed by RT-qPCR/qPCR and next generation sequencer analysis, during pre-flight, in-flight and post-flight.
9-18 months

Collaborators and Investigators

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

Sponsor

Yakult Honsha Co., LTD

Collaborators

Japan Aerospace Exploration Agency

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 (Actual)

October 1, 2015

Primary Completion (Actual)

April 1, 2022

Study Completion (Actual)

April 1, 2022

Study Registration Dates

First Submitted

November 1, 2015

First Submitted That Met QC Criteria

November 25, 2015

First Posted (Estimated)

December 1, 2015

Study Record Updates

Last Update Posted (Estimated)

November 25, 2025

Last Update Submitted That Met QC Criteria

November 19, 2025

Last Verified

November 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Probiotics

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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