Vitamin C (also known as ascorbic acid) is important in your diet. However, most doctors and scientists believe taking vitamin C won’t help you in preventing a cold. There’s no doubt that many people are convinced that taking large quantities of vitamin C can help ward off a cold; and the theory has been tested in several studies involving children and adults. However, no conclusive studies have shown that large doses of vitamin C can prevent colds. There is some evidence that it may help to shorten the length of time you are sick and reduce the severity of symptoms slightly. So, if you get a cold, feel free to drink all the orange juice you want. Fruits and vegetables such as raspberries, bell peppers, pineapple, broccoli, spinach and tomatoes are also great sources of vitamin C.