Vitamin supplements can increase risk of cancer and heart disease. Dietary supplements, such as over-the-counter multivitamins, do “more harm than good” and can increase the risk of developing cancer and heart disease, according to research in the US.

Which vitamins can cause cancer?

Evidence indicates that deficiencies of iron and zinc, and the vitamins folate, B12, B6 and C, can cause DNA damage and lead to cancer. New animal bioassays of nutritional deficiencies are needed, particularly for studying cancer.

What are the risks of taking supplements?

Taking more than you need costs more and might also raise your risk of side effects. For example, too much vitamin A can cause headaches and liver damage, reduce bone strength, and cause birth defects. Excess iron causes nausea and vomiting and may damage the liver and other organs.