The Russians were also interested in going to the moon. Their planned moon rocket, the N1, was a very explosive dud unfortunately, blowing up in the first stage in all four launch attempts, with one example falling back onto the pad right after launch, destroying the pad in what can be considered the largest non nuclear explosion ever in terms of energy release.
No moon rocket, no moon mission.
However, before they gave up the project, they sent unmanned versions of their equivalent of the Apollo 8 CSM to test several things, including re-entry.
Among other things they tested was living creatures reaction to the conditions, including human cell cultures, such as HeLa cells and fibroblasts. As well, they included an experiment to measure the radiation levels directly.
They
found that: "The comparison of the dosage evaluations with the permissible values allows the conclusion that, should no solar flare occur, seven-day flights along the trajectories of Zond-5 and 7 probes are safe from the radiation point of view."
So that's third party evidence that, if you follow the right trajectory, as everyone here has been saying, the Van Allen Belts are safe enough to traverse. Just who is this alleged "Everyone" you speak of, allancw?