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.
Max "official" safe daily limit is 4000 IU currently, but the only studies I'm aware of where actual toxicity was reported started at something like 40,000 IU daily for months. Vitamin D is likely pretty safe.
No, the estimated RDA based on EPIC series of studies is 3000 IU daily and it's suspected to be on the lower side due to old people being bit overrepresented. This based on all cause mortality, various European subjects. Intake estimated by direct multiple blood levels.
Vitamin D intake vs mortality followed a very shallow U curve (almost J) and minimum was between 2000 and 4000 IU.
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.