The average adult gets between two and four colds a year. That's a lot of coughing, congestion, headaches, and runny noses. Some of this suffering is unavoidable — there's no cure for a cold — but that doesn't stop everyone from swearing by one remedy or another: loads of vitamin C, hot tea, a hard run and a long sauna, zinc, a hefty pour of whiskey, a bowl of chicken soup. But what actually stops, prevents, or shortens colds? We talked to a number of experts and pored over the hard science (there are 65 serious studies on vitamin C alone) to get to the bottom of what really works.