Vitamin and mineral supplements can be used to reduce the risk of certain diseases. For example, women who take moderate supplements of folic acid prior to and during pregnancy help to decrease the risk of their infant being born with neural tube defects. Folic acid may also help reduce the risk of colon cancer and heart disease. Vitamin C is another important supplement, which plays a role in controlling infections and helps the body make collagen, a tissue needed for healthy bones, teeth, gums and blood vessels. The established recommended daily allowance (RDA) provides the recommended daily intake of vitamins and minerals for proper nutrition. It is important to establish the relationship between supplements, the disease and its symptoms. Vitamin toxicity can happen when a person develops symptoms and side effects from taking high doses of vitamins. Mega doses of vitamin d, A and B6 can be very harmful, or even fatal. It is important to speak with your physician or pharmacist before taking any supplement, specially if you are currently taking any prescription or over-the-counter medicines. Some supplements may interacts with medications and cause potentially serious side effects.