Magnesium Alterations in Human Spaceflight.

Introduction: Magnesium is essential for numerous physiological processes. Changes in magnesium homeostasis during spaceflight could impact astronaut health, particularly as mission durations increase. This review examines trends in serum, urine, and intake-based magnesium data from published human spaceflight studies.

Methods: A systematic search was conducted using scientific and government agency databases. Inclusion criteria were English studies of adult astronauts in spaceflight reporting magnesium measurements (serum, urine, or intake). Magnesium data were extracted across in-flight, landing day, and postflight time points. Percent change from baseline was calculated and regression analyses evaluated trends over time.

Results: A total of 20 studies were included. In-flight data showed an early increase in urine magnesium (+19.3% ± 3.6%) without significant trends over time, while serum magnesium remained stable initially but increased with longer flight duration (β = 0.03). On landing day, serum magnesium was similar (-3.92% ± 0.94%) with a nonsignificant trend toward baseline thereafter (β = 0.15), whereas urine magnesium decreased significantly (-30.01 ± 6.74%), followed by a significant trend toward baseline over time (β = 1.16).

Discussion: Microgravity may be associated with early renal magnesium losses and a progressive increase in serum magnesium. This could be a result of initial fluid shifts and neurohormonal changes, followed by progressive loss from bone and muscle, potentially exacerbated by insufficient dietary intake. Data are limited to missions less than 6 mo, leaving long duration consequences unknown. Further research is needed to confirm trends and explore underlying mechanisms. Diaz TE, Sullivan RD, Ashworth ET, Buesking SC, Haggarty AM, Carmichael BDM, Singh G. Magnesium alterations in human spaceflight. Aerosp Med Hum Perform. 2025; 96(10):919-930.