Yes they work but only on a placebo level. There are two ways to view placebo, the negative view as in gimmick or the positive way as in the science behind the placebo effect.
Everyone harps on the gimmick and NOT one research organization studies the science behind the placebo effect. The science behind the placebo in regards to vitamin and mineral supplements is the science of the human immune system which cannot be patented or sold therefore is completely disregarded by the whole medical industry including the alternative medicine industry.
When natural medicine works it is pure placebo which means it is the person's own immune system doing the work. However because there is no one trained in the art of placebo anymore alternative medicine as become as useless as western medicine when it comes to cures. There was a time not so long ago when natural practitioners were capable of curing through the science of placebo but now they are all taught to rely on the products not the science. Granted the best practitioners had no idea their cures where part of the science of placebo which is why they have all become virtually ineffective offering only temporary relief at best. This is because all natural medicine has become product gadget oriented instead of passion oriented. At least with passion a person has a better chance of delivering a placebo effect, even one that cures.
I could make a hub about it and it would leave no room for dispute because I know the science behind the actual immune system but the hub would be a flop because no one wants to see immune science made available because it would destroy the complete medical industry with the exception of trauma. It would also cause a population explosion.
Actual healing requires no technology or products.
The vitamins and minerals we need comes from our food and they are helpful but they do not cure or boost immunity without generating a placebo effect. A sugar pill with a great label will work equally well.
Those blaming food for our weakened health do so at the destruction of the truth. I will say this, the most harmful foods today are any foods containing carbs or sugars and that includes blueberries. Carbs and sugars feed fungus and fungus kills more people than any other pathogen and I am not speaking of candida, I'm speaking of all the fungus that each and everyone of you is saturated with.