Vitamin C, or ascorbic acid, is a water-soluble vitamin well known for its role in supporting a healthy immune system. Because your body cannot make vitamin C, it must come from the foods you eat every day or through supplementation. Though it may not keep you from catching a cold, there is some evidence that high doses of vitamin C may decrease the length of cold symptoms by as much as one to one-and-a-half days for some people. However, other studies did not result in the s