Sorry. I've updated the comment and added the link. As far as I understand taking 10x the RDA won't have side effects because that's not an overdose, that's the correct dose and the RDA is a mistake.

I haven't tried this myself yet though. I am taking 1000 IU now (and it makes a difference I can feel already as compared to taking nothing or 1 RDA) while waiting for the 10'000 IU pills to get delivered from eBay. I didn't knew I actually need this much before reading the paper by the link.