One small supplement for man, one giant leap for mankind

Spending long periods of time in space can wreak havoc on an astronaut's health, including their gut health. The health dangers are so wide ranging that they could prevent long-distance missions, such as a Mars landing.

However, a new review published in Frontiers in Physiology,​ highlights suggests that the utilisation of a gut healthy diet, with supplementary pre- and probiotics could protect astronauts from the rigours of space travel. In fact, they suggest that finding out which microbes provide the most benefit and the best way to use them could be key to reaching the red planet in one piece.

Authored by Professor Silvia Turroni, of the University of Bologna, Italy, and Professor Martina Heer of the University of Bonn, Germany, the report notes that among the medical events that occurred from 1981 to 1998 on space shuttle flights, gastrointestinal problems accounted for 8%​ and rank third after space adaptation syndrome (42%) and neurosensory alterations (17%).

Turroni et al review literature surrounding the disruptions in the gut microbiome​ that occur during space travel and the use of pro or prebiotic supplements for some of the key health issues experienced by astronauts, including undernutrition, cognitive decline, muscle/bone atrophy and loss of immune function.

The international team of researchers conclude that the right supplements couldcontribute to the success of long-term missions.

Their report states: "In light of the crucial role of intestinal microbes in maintaining metabolic, immunological and neurological health, as well as of muscles and bones, strategies aimed at recovering and preserving a eubiotic microbiota profile might help mitigate the unwanted effects on the space traveler’s body, thus contributing to the success of long-term missions. ​

"This could be achieved by optimizing diets to ensure adequate energy and fiber supply for SCFA production, while avoiding nutritional imbalances, as well as by integrating them with prebiotics, bioactive compounds and probiotics for potentially synergistic effects. ​

"Aside from prebiotics and bioactive compounds, probiotics, both traditional and next-generation ones, during spaceflights can be postulated as a non-invasive alternative –given that safety is assured- to protect space travelers against altered metabolism, satiety impairment, immune dysregulation, circadian rhythm changes, bone and muscle loss, as well as neurobehavioral disorders. ​

"Additional mechanistic studies under microgravity and simulated space environment, but also intervention studies and clinical trials directly in space travelers are needed to support current evidence on pre-, probiotics or combined strategies on Earth, before these microbiota manipulation tools can be integrated into spaceflight clinical practice."​

Undernutrition

One very common risk with space travel, is undernutrition, which can then lead to cognitive ability, muscle atrophy, immune function and more. 

The review points out that appetite and food intake is intrinsically linked to the composition and function of the gut microbiome perhaps due to the fact that most of the microbes that inhabit the body provide benefits to the entire host-microbe system​, including production of important resources, bioconversion of nutrients, and protection against pathogenic microbes. 

Muscle/bone atrophy

The review notes that it has been demonstrated​ that activation of inflammation and innate immunity by gut microbiota components increases the production of TNFα and the osteoclastogenic factor RANKL (receptor activator of nuclear factor kappa-B ligand) in bone, and as a consequence, promotes bone loss. This mechanism is said to be dependent on bacterial peptidoglycan sensing by the NOD receptors NOD1 and NOD2.

A study in mice​ showed that gut colonisation of germ-free infant mice with a specific strain of Lactobacillus plantarum​ (L. plantarum​ WJL) was able to recapitulate juvenile growth, including radial and longitudinal bone growth. The proposed mechanism for this effect is a strain-dependent stimulation of the somatotrophic axis and the production of IGF-1. The potential effects of these bacterial strains on osteoporosis have not been reported so far.

Considering these relationships between the gut microbiome and bone homeostasis, probiotics are now suggested​ as an attractive strategy to protect against bone loss. 

Probiotics, for instance, can modulate the synthesis of vitamins and co-enzymes that are required for matrix formation and bone growth including vitamin D, K, C and folate. Furthermore, by producing SCFAs, they reduce intestinal tract pH and consequently increase mineral absorption​. 

Mental health

The gut microbiome has been reported to influence stress physiology and psychology, mood, cognition, and behaviour, leading to the terms 'gut-brain axis' and 'psychobiotics'. 

The current review suggests strategies aimed at maintaining a healthy microbiome might therefore be helpful in mitigating unwanted neurobehavioral effects of space travel.

Although most of the research concerning intestinal microbiome and mental health is based on rodent studies, human studies​ have provided preliminary evidence that orally administered probiotics may support mental health. 

Source: Frontiers in Physiology​ 
Silvia Turroni et al
"Gut Microbiome and Space Travelers' Health: State of the Art and Possible Pro/Prebiotic Strategies for Long-Term Space Missions" ​
DOI: 10.3389/fphys.2020.553929​