Impact of diet on human nutrition, immune response, gut microbiome, and cognition in an isolated and confined mission environment.

Long-duration spaceflight impacts human physiology, including well documented immune system dysregulation. The space food system has the potential to serve as a countermeasure to maladaptive physiological changes during spaceflight. However, the relationship between dietary requirements, the food system, and spaceflight adaptation requires further investigation to adequately define countermeasures and prioritize resources on future spaceflight missions. We evaluated the impact of an enhanced spaceflight diet, with increased quantity and variety of fruits, vegetables, fish, and other foods rich in flavonoids and omega-3 fatty acids, compared to a standard spaceflight diet on multiple health and performance outcomes in 16 subjects over four 45-day closed chamber missions in the NASA Human Exploration Research Analog (HERA). Subjects consuming the enhanced spaceflight diet had lower cholesterol levels, lower stress (i.e. cortisol levels), better cognitive speed, accuracy, and attention, and a more stable microbiome and metatranscriptome than subjects consuming the standard diet. Although no substantial changes were observed in the immune response, there were also no immune challenges, such as illness or infection, so the full benefits of the diet may not have been apparent in these analog missions. These results indicate that a spaceflight diet rich in fruits, vegetables, and omega-3 fatty acids produces significant health and performance benefits even over short durations. Further investigation is required to fully develop dietary countermeasures to physiological decrements observed during spaceflight. These results will have implications for food resource prioritization on spaceflight missions.

Assessment of urinary N-telopeptide: point-of-care testing, sample types, and relationship to urinary helical peptide excretion.

BACKGROUND: A point-of-care (POC) device would be useful in the space program for measuring N-telopeptide (NTX), a marker of bone resorption. This study was done to establish whether NTX measurements from a POC device compare favorably with standard (ELISA) techniques. We also compared results from fresh and frozen urine samples, samples collected on consecutive days, and second voids (of the day) and 24-h urine pools. Helical peptide (HP), another crosslink, was compared in second voids and 24-h urine pools. METHODS: Ten subjects collected urine for 96 h. NTX was measured with the POC device and by ELISA, and HP measured by ELISA. Seven subjects collected 24-h urine pools, and samples were analyzed fresh and after 27 days of freezing. RESULTS: Excretion of NTX was greater (P<0.05) when measured by the POC device than when measured by ELISA, but was not different between second voids and 24-h urine pools, or among days. HP was similar in second voids and 24-h pools. Less NTX (P<0.05) was found in fresh 24-h pools [mean (S.D.) values, 38.4 (11.6) and 33.6 (9.2) nmol/mmol creatinine for the POC device and ELISA] than in previously frozen 24-h pools [42.7 (17.4) and 41.5 (12.5) nmol/mmol creatinine for the POC device and ELISA]. CONCLUSIONS: Comparisons between NTX measurements from frozen and fresh samples and those analyzed by POC and ELISA techniques should be made with caution.