8 Top-Rated Vitamins That Will Give You a Boost — All From Amazon

The vitamin: Nature's Way Vitamin C ($14)

Why people take vitamin C: Helps support immune system health and promote iron absorption.

What reviewers are saying: One reviewer liked how it also helped them digest food. "This is a fantastic vitamin C. I use it to help absorb nutrients from my meals, as directed by my doctor. I also use it when I have a cold to bolster my immune system and it works like a charm."