Retinoids to protect from Cosmic Rays?

Scientific American, November 2007:

NASA has worried that cosmic rays could undermine a human voyage to Mars. New simulations and calculations, though, suggest that such lengthy exposure to space radiation may pose only half the health risk that NASA had expected.

...the lower a proton’s energy, the more damage it does. Apparently, lower-energy protons, which travel more slowly, have more time to interact with tissues. In lowering its assessment of risk, NASA also factored in astronauts’ better-than-average health and switched from “whole-body” radiosensitivity to organ-by-organ measurements, where new studies have found lower risks for lungs, breasts and the blood system.

...Possible drugs include retinoids — vitamins that work as antioxidants — and compounds that delay cell division long enough for damaged cells to repair themselves before they can propagate mutations.

Something to consider storing in your bunker, but it might take some finding.