Vitamin C: megadose dangers

All it takes is a glass of orange juice, an apple or one serving of broccoli to meet the recommended daily allowance (RDA) for vitamin C. Taking "megadoses," or more than 10 times the RDA, of vitamin C supplements may cause nausea, diarrhea and, as new research suggests, be harmful to people who have cancer.

A study in the journal of Cancer Research suggests that vitamin C has the potential to interfere with chemotherapy treatments. While vitamin C generally boosts the immune system and protects healthy cells from illness, researchers found that large doses of vitamin C in tablet form also protected cancer cells.

It's rare that people consume too much vitamin C from their diets. If you do consume too much, your body flushes it out through your urine. People who are healthy and eat a well-balanced diet typically do not need vitamin supplements.