Completed

NCT Number: NCT02618005

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.

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Key information

Conditions

Immune Function and Intestinal Microbiota

Age range

25 year–80 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Japan Aerospace Exploration Agency

Ibaraki, Japan

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Probiotic capsule

Dietary Supplement

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)

Primary outcomes

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.
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.
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.

Sponsors and collaborators

Lead sponsor

Yakult Honsha Co., LTD

Industry

Collaborators

Japan Aerospace Exploration Agency

Registry information

Official study title

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

Important dates

Study start: 2015
Primary completion: 2022
Study completion: 2022
First posted: Dec 1, 2015
Registry last updated: Nov 25, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.