There is no way that's what they meant. 50k is an absurdly large dose that's way outside the safe intake range. 10k is used sometimes under medical supervision and even then it's a very short term measure. For long term intake, 4000IU is a widely accepted safe upper limit. 50k is an order of magnitude more than that.
There's plenty of documentation of people taking 50k for a period of time and having no side effects. There's been something like a dozen trials using high doses like this to treat TB, and they're usually successful, with no significant negative symptoms.
Conversely, some studies have shown that 4k IU does contribute to hypercalcemia in a small number of cases (4 per 1000). So actually 4k is deemed "not completely safe" as a limit.
The point is, the amount you take needs to be adjusted by a clinician, as the safe range for you is unknowable otherwise.
