I followed my doctor's advice and took some extra vitamin C after breaking my wrist this winter. Not only did my wrist heal in record time (I was out of the cast in a month), but I never got a single cold or the flu. How does that work? Was it just because I thought I was doing myself some good taking it?
Your question of how does vitamin C work to prevent colds and flu as well as speed up bone healing is one that many scientists are studying to solve. Experts in this area aren't entirely sure the exact mechanism by which vitamin C accomplishes both things. We do know that it is an antioxidant that can boost the immune system to help fight bacteria and viruses associated with upper respiratory infections and the flu.
What is an antioxidant? To understand antioxidants, we have to look at oxidation and free radicals. Oxidation is the process by which an oxygen atom loses an electron forming an unstable molecule called a free radical. Electrons like to be paired and the loss of one in the pair making the oxygen atom unstable must be repaired before further harm is done.
Vitamin C comes in and gives up an electron without becoming unstable itself. That's what makes vitamin C an antioxidant. Without antioxidants to quench the free radical's need for an electron, the free radical goes around stealing an electron from other oxygen atoms making yet another free radical. A destructive chain of reactions occurs as more free radicals are formed. Apples and bananas that turn brown when left unprotected is a visible example of oxidation. So is rust on the body and fenders of a car exposed to salt used on the roads during the winter.
Just the act of breathing and daily cellular functions create free radicals. Any type of stress can result in extra free radicals that the immune system must deal with as well. With enough stress and the formation of enough free radicals, the immune system can get overwhelmed by microbes that cause cold and flu symptoms.
Vitamin C is also important in the formation of collagen, the basic building block of soft tissue and bone. When a fracture occurs, the body mounts an immediate inflammatory response to start the healing process. Inflammation results in the free oxygen radicals we just talked about -- often, more than the body can handle effectively. Vitamin C may reduce the number of free radicals that form as a result of the fracture and subsequent inflammatory healing process. The final outcome is a faster healing response like what you evidently experienced.
Vitamin C is a safe, effective, and relatively inexpensive way to speed up healing and recovery when there aren't complicating factors. It's not a magic cure -- patients must still wear a splint or cast and receive follow-up hand therapy when needed.