Well, i dont think believe that you can really get sick taking to much vit C since its water based. The ones that can lead you to get sick are A,D,E,K. These are fat soluble and not water soulabel. Meaning you dont just piss them outta your system.
If your get sick all the time I reccomend that you use all Antioxidants, collectively these will help build up your immune system. Antioxidant vitamins E, C and beta carotene (a form of vitamin A), and i would also recommend zinc as well.
How Antioxidants Work
As cells function normally in the body, they produce damaged molecules — called free radicals. These free radicals are highly unstable and steal components from other cellular molecules, such as fat, protein, or DNA, thereby spreading the damage.
This damage continues in a chain reaction, and entire cells soon become damaged and die. This process is called peroxidation. Peroxidation is useful because it helps the body destroy cells that have outlived their usefulness and kills germs and parasites. However, peroxidation, when left unchecked, also destroys or damages healthy cells.
Antioxidants help prevent widespread cellular destruction by willingly donating components to stabilize free radicals. More importantly, antioxidants return to the surface of the cell to stabilize rather than damage other cellular components.
When there are not enough antioxidants to hold peroxidation in check, free radicals begin damaging healthy cells which, in turn, can lead to problems. For example, free radical damage to immune cells can lead to an increased risk of infections.
Antioxidants and Immune Response
Because antioxidants play a key role in minimizing damage to cells, such as those that make up the immune system, recent research examined the benefits of certain antioxidants on the immune response of dogs and cats. The results of these studies indicated that antioxidants are important in helping dogs and cats maintain a healthy immune system.
The research also showed each antioxidant benefits the immune system uniquely, so one antioxidant at high levels is not as effective as a group of antioxidants acting together.