This is one of those facts that sounds scary but it's really hard to interpret. Prostate cancer is extremely common; I've heard that upwards of half of men that die of old age have developed prostate cancer, though not all have gotten to the point where it's been noticed and diagnosed. A quick google says that 1 in 7 men will be diagnosed with it.

So on the surface it sounds like the vitamin will kill you, but in reality what if it's helping enough that you're now living long enough for the prostate cancer to actually become a problem? What if people that take vitamins are more health-aware and more apt to get regular physicals, increasing their "occurrence" of cancer?

There's a lot of variables that the article doesn't discuss and I'm not confident they have been controlled for.

B is divided into different forms. Some of them you can take a lot of (e.g. B12), while others you should be careful with (e.g. B6). I suggest you do some research.

Is that sort of thing an indefinite prescription, or for like a month?