I always have some Vitamin C with me.
Whenever I stat feeling under the weather I take extra and I rarely get sick.
When you chose your Vitamin C be sure to get one with a natural source and not only ascorbic acid as it's only one of 12 compounds that make up Vitamin C complex.
A very good source is rose hips powder. I use it in my morning smoothie.
Camu camu contain even more Vitamin C but it's abit to expensive for me.
It's almost impossible to take to much of Vitamin C. The only thing that can happen is that you will get an upset stomach and then you have to go to the bathroom if you know what I mean ☺