A: Research on using moderate and megadoses of vitamin C has suggested this supplement can reduce the severity and duration of a cold but not the frequency. Vitamin C is a water-soluble vitamin. As such, excess quantities are not stored in the body but are instead excreted through the urine. Most people will not be harmed by taking large doses of vitamin C (more than 1,000 milligrams daily). However, once your body adjusts to megadoses of C, you will also excrete large amounts of it. It then takes time to readjust to lower doses of vitamin C.

There is a theoretical concern your unborn baby could develop the capacity to excrete the excess vitamin C it obtains through your large intake. After delivery, the baby would continue to excrete vitamin C, even though sources of vitamin C through breast milk or formula are now lower. Theoretically, it is possible for a baby to develop scurvy (a vitamin C deficiency disease) if his mom used high doses of C in late pregnancy. Another concern about taking megadoses of vitamin C is that some people respond with diarrhea and gastrointestinal distress. Be sure to talk to your doctor about your desire to continue using Vitamin C.