Nutrition and Human Space Flight: Evidence From 4–6 Month Missions to the International Space Station

Abstract

Objectives2020 marked the 20th anniversary of a continuous human presence off the planet. Space flight is challenging, with environmental stressors, a closed food system, and adaptations affecting virtually all body systems. Our objective was to evaluate the time course of biochemical changes during flight, the effects of countermeasures, and the relationship between diet and physiological outcomes. MethodsBlood and urine samples were collected before, during, and after flight from 65 astronauts. These were analyzed for a broad-based survey of physiological systems. Detailed diet records were available from 27 astronauts using an iPad App designed for use on ISS. ResultsThe average intake of fruits and vegetables was lower than recommended (2.6 ± 0.9 servings per day), but intakes correlated with outcomes at landing. Specifically, higher intakes were positively correlated with vitamin C status (R2 = 0.43, P < 0.05), and negatively correlated with inflammation (Interferon-γ, R2 = 0.76, P = 0.001) and oxidative stress (malondialdehyde, R2 = 0.51, P < 0.05). Despite limited dietary sources and no UV light exposure, 800 IU vitamin D/d supplements maintained vitamin D status (serum 25OH-vitamin D was 78 ± 4 nmol/L during flight). Cholesterol (298 ± 163 mg/d) and saturated fat (26.1 ± 11 g/d, 10.4 ± 3.1% of kcals) intakes were associated with a 10% and 14% increase in circulating total and LDL cholesterol, respectively (P < 0.001). Perhaps the most notable finding is that one-carbon biochemistry is altered in astronauts who experienced ophthalmic changes during and after flight, where circulating homocysteine concentrations were higher in affected astronauts compared to unaffected astronauts (P < 0.001), and these differences existed before flight. ConclusionsEvaluation of countermeasure effectiveness and individual and group responses to spaceflight will continue to be important on the ISS and will inform future space programs including Artemis and Gateway missions to the moon. Those efforts will require similar types of comprehensive assessments to allow the next steps in human exploration of space. By uniting nutrition with other disciplines, the importance of diet in heath can be further enlightened, with potential implications for both space explorers and for those remaining on Earth. Funding SourcesThis research was funded by the NASA Human Research Program and DLR.