In my experience doctors or nurses rarely talk to their patients about the importance of taking nutritional supplements. But the majority of them take supplements themselves. Here is a study that reports as many as 79% of doctors and 82% of nurses take supplements.
Why do I take them? I believe that our fruits and vege's simply don't have in them what they used to have in terms of minerals and vitamins. I also admit I don't eat as many fruits and vege's as I should. Most people don't. So I think it is good insurance to add supplements when I eat.
