"I take vitamin C every day 1000mg especially when I can remember it, even more when I have a cold and that seems to help a lot."

Lots of people swear that vitamin C can keep colds at bay. They're in good company. Nobel prize-winning scientist Linus Pauling believed it too. So the idea would seem to be nothing to sneeze at. But the cold, hard facts suggest otherwise.

A review of 30 studies involving more than 11 thousand subjects found that daily vitamin c generally did not ward off colds.

But there were some exceptions: for marathon runners, skiers, and soldiers in frigid conditions, the vitamin appeared to cut their risk of colds by half.

As for the effect on symptoms, it's slight. In studies regular vitamin c users had colds that were shorter, on average, by one day or less.

Those who started vitamin c once they felt sick did not seem to benefit at all-unless they took a massive dose of 8000 mg.

That's far more than the 2000 mg a day upper limit considered safe for adults. Above that, vitamin c can cause stomach upset and kidney stones.

Also, it's best not to take more than 500 mg at a time, since that's about all the body can absorb.

As long as you don't overdo it, there's probably no harm in popping vitamin c as a defense against colds. But the best way to get the vitamin is through foods like oranges. That way, even if you aren't preventing colds, you'll still be doing a favor for your health and your tastebuds.