jsc2024e050837 (7/26/2024) --- Frozen blood samples collected aboard the International Space Station after return to Earth are part of the B Complex: A Nutraceutical SANS Countermeasure (B Complex) investigation. This study tests whether a daily B vitamin supplement can prevent or mitigate SANS and also assesses how an individual’s genetics may influence the response. The results could help maintain astronaut vision and health on future long-duration missions, including those to Mars.