While this article seems to have a lot of factual errors, their core contention -- the root of the justification for the article's existence -- is that vegans have a lot of deficiencies. That is the point that needs to be questioned, and often seems like scaremongering more than reality.

And as always, it's pretty simple to take a multivitamin and call it a day, presuming one isn't so militant that an ingredient in that is objectionable.