In a word: No. Researchers have yet to find a magic bullet that will protect you from the common cold, and there's no evidence that loading up on vitamin C—whether by drinking OJ or taking a supplement—will do the trick, says Dr. Christine Laine, senior editor of the Annals of Internal Medicine, a scientific journal.
The best way to avoid a case of the sniffles? Try to relax. In addition to the old stand-bys like eating a balanced diet, exercising and getting enough sleep, studies have shown that people who are stressed-out have a weakened immune system and might be more likely to catch a cold than those who feel calm and in control.