Do you start popping vitamin C supplements at the first sign of the sniffles? For years, conventional wisdom has prompted many people to take vitamin C for avoiding a cold. Unfortunately, the science on this subject is much less clear. In fact, most research does not support using vitamin C for cold prevention or for shortening the length of your cold. But some studies do reveal possible small benefits. Taking large doses of vitamin C could lower the number of days you have a cold by one. That's not much but when you feel lousy, even one day is worth a little pill popping.

Think foods first for vitamin C. Most adults need 75 to 90 mg of vitamin C a day to prevent a vitamin C deficiency. But you can get a lot more than that without any serious side effects. Some studies show that a diet high in vitamin C foods and drinks (around 500 mg a day) may be related to a lower risk of some cancers. Those studies are far from certain. But eating a lot of high vitamin C foods is a good idea. Here are the best sources of C:

  • 1/2 large yellow pepper: 170 mg
  • 1 cup orange juice: 95 mg
  • 1 cup whole strawberries: 84 mg
  • 1 orange: 75 mg
  • 1 medium kiwifruit: 74 mg
  • 1/2 large green pepper: 70 mg
  • ½ cup steamed broccoli: 58 mg
  • ½ cup cooked Brussels sprouts: 48 mg
  • 1 baked potato: 31 mg 
  • The few studies that have shown small benefits for vitamin C supplements and cold prevention used doses of around 1000 mg a day. Again, most studies do not show that vitamin C supplements are helpful in preventing colds. But it is safe to take supplements. Here are vitamin C supplement guidelines:

  • Don't go over 2000 mg of vitamin C a day
  • Cut back if you experience nausea or diarrhea
  •  High doses of vitamin C can also increase the risk of kidney stones
  • Remember, most research does not show that taking vitamin C supplements is helpful to your health. So, concentrate on a healthy diet with at least one or two high vitamin C foods a day. If you want to take supplements, follow the safety guidelines.

    Beth Kitchin MS RD
    Assistant Professor
    UAB Department of Nutrition Sciences