A good question but one that lacks a definitive answer. I take vitamin and mineral supplements. Can I say with certainty that they keep me healthy? I don’t know. I’m rarely sick. Maybe I’ll have a cold for a couple of days every few years. Is that because of the vitamins and supplements or is it genetic? My dad was rarely sick as well and I don’t think he took any supplements.
Also if you do a little research, there are conflicting studies on just about every supplement out there as to whether we need them or not. I found it hard to find a consensus except that unless your doctor prescribes something for you, you should try to get most of your vitamins and minerals from the food you eat.