system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can medicine or multivitamins target a specific part of the body when it's all consumed the same way?
gpt
They cannot target a specific part of the body. However, if you have some sort of deficiency that shows up most prominently in a specific part of the body, then taking the multivitamin or supplement can reduce the deficiency and "heal" the affected part simply because that's the part that hurts. Same for painkillers; they dull the pain everywhere, but you only notice the effect where you were feeling pain.