Q: Dear Dr. Mao,
How does Vitamin C factor into immunity and preventing colds?
A: Vitamin C is the most famous of all natural treatments for colds. Numerous studies have found that vitamin C supplements taken at a dose of 1,000 mg daily or more can significantly reduce symptoms of colds and help you get over a cold faster. Benefits appear to be greater for children than for adults, and the exact amount of the benefit varies widely between studies.
There is no real evidence that vitamin C can prevent colds in general. However, there are two exceptions to this. One is the “post-marathon sniffle.” Heavy endurance exercise temporarily weakens the immune system, leading to a high incidence of infection following marathons and triathlons. There is some evidence that vitamin C can prevent such colds.
The other situation in which vitamin C might help prevent colds is when you are deficient in the vitamin. In such cases, making sure to get your dietary allowance might help keep you healthier.