Interesting. Linus Pauling said the same thing in the '70s. He took megadoses of Vitamin C and then died of cancer. Aside from that, it can cause headaches, nausea, vomiting, kidney stones and other unpleasantness. And it can interfere with the metabolism of some medications.
That's exactly why I am doing my own research before writing my review of the movie. I have heard all of that as well. The differences that these doctors and scientists are maintaining are administering the vitamin C via IV. On doctor said he gave he wife 300 treatments and she felt very healthy...until she died of her breast cancer.