I used to get every flu and cold going around, too, right through summer. Then I moved and got a new chiropractor who said that because of the stress on my adrenal glands from the scar tissue in my back, I need to be taking large doses of vitamin C -- as in, 3 grams or more per day, every day. He said that when a body is under stress, the adrenals can consume all the available vitamin C very quicky in the production of adrenaline and cortisol, leaving nothing for the immune system to use. Then the body gets sick, which puts more stress on the body, and it becomes a vicious cycle.

Since taking at least 3 grams of vitamin C per day, though, I've rarely gotten a cold in the past two years, and when I do, I just increase my vitamin C intake to about 6+ grams or what my bowels can handle (tmi: the only side effect of taking "too much" vitamin C is that you'll get, er, "soft stool" /tmi) and it clears up fairly quickly instead of hanging on for a month like before.