Many people have to take supplements like Iron supplements for a long period of time, and if that is the kind of supplement you are referring to you cannot get addicted to them.
So, it's pretty much safe to take multivitamins/minerals once a day for a longer period of time? A friend of mine said it would be smart to switch from one brand to another from time to time.
Nutritional supplements aren't addictive, unless you start getting into really esoteric herbals, perhaps. I don't supplement for nutrition, but I do take glucosamine as I've got a lot of joint deterioration and it helps.
I used to take that Glucosamine/Chondroitine/MSM combo and it really works good. It works good for joint strengthening and for fixing problems as well.
