system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: There have been many stories recently about multivitamins being ineffective. But I have a family member who had an iron deficiency, was prescribed an iron supplement, and it worked. What gives?
gpt
What gives is there is a difference between being prescribed medicine to combat a specific illness, disease or deficiency, and a person without such a condition taking a multivitamin for general health and well-being or as a preventative measure for diseases like cancer or heart disease.

That is, if you have a condition where you need iron or you'll die. Then yes, getting iron will help.

But if you don't, then taking iron isn't going to do anything for you.