The Microbiome: The Forgotten Organ of the Astronaut's Body — Probiotics Beyond Terrestrial Limits

Amir Ata Saei; Abolfazl Barzegari


Future Microbiol. 2012;7(9):1037-1046. 

In This Article

The Human Intestine & the Microbiome

Today 'gut health' is a term increasingly used in the medical literature to describe effective digestion and absorption, the absence of gastrointestinal lesions, presence of normal intestinal microflora and proper immune function.[5] However, from a scientific point of view, it is still extremely unclear what gut health is or how it can be defined and/or measured. The interactions between the gastrointestinal barrier and the microbiome appear to be a complex mechanism that assists in maintaining gut health. The gastrointestinal tract contributes to digestion and absorption of nutrients, minerals and fluids, osmoregulation, endocrine regulation and host metabolism, mucosal and systemic tolerance, immunoenhancement, defense against potential pathogens and harmful substances, signaling from the periphery to the brain, and detoxification of toxic molecules originating from the environment or the host.[6] Recognition of the importance of gastrointestinal health and microflora can be an important asset to astronauts' health.

Across the large surface of the digestive tract, healthy and pathogenic bacteria compete for dominance. With such a huge exposure area, the immune system has a hard task of hindering pathogens from entering the blood and lymph. The presence of a balance between beneficial and potentially harmful bacteria is considered normal and contributes to a dynamic and healthy human gut. One way to maintain this homeostasis is to introduce helpful bacteria or probiotics. After the first suggestion of the health benefits of probiotics in the early 20th century by Nobel Laureate Metchnikoff, many bacterial strains have been clinically tested as potential probiotics.[7] Probiotics are thought to play a health-promoting role by improving intestinal microbial infections.[8–10] The surface area, apparent balance of microflora and health impact of the human gut reminds us that this complex organ must not be forgotten as one factor in long-duration spaceflight health.