"no medical studies"? That seems like a very interesting claim, but the article you linked doesn't support it much, instead just listing a few studies which found that specific vitamins failed to improve health in specific areas.
If taking vitamins regularly was something that improved our health, we should be able to measure that. But as far as I know, we haven't been able to.
"Usage patterns, health, and nutritional status of long-term multiple dietary supplement users: a cross-sectional study"
It was conducted by researchers from the University of California (Berkeley)
You could argue that breathing more air improves heath ... because it works for people who are underwater.