Despite the popular belief that vitamin C can cure the common cold, the scientific evidence for this is limited. A few studies suggest that taking vitamin C supplements at the beginning of cold symptoms, or just after possible exposure, can shorten a cold or ward it off altogether.

However, most studies conclude that vitamin C does not prevent or treat the common cold. Vitamin C may only be useful in case of a cold if you have low levels of this nutrient to begin with. The likelihood of success may be very individual -- some people improve, while others do not.

People with kidney disease should avoid vitamin C supplements. Most experts advise that you meet your daily vitamin and mineral requirements by eating a balanced diet.