There is some evidence that foods with high levels of antioxidants, such as fruit and vegetables, offer a protective effect against certain cancers. People who eat recommended levels of fruit and vegetables have been shown to be at lower risk of cancers of the mouth, pharynx, larynx, oesophagus, stomach and bowel. Fruit may also help protect against lung cancer. However, this has not been shown with antioxidants in concentrated forms (i.e. supplements). And for people undergoing chemotherapy or radiotherapy treatments, such supplements may be harmful. Many people assume taking micronutrients or multivitamins high in antioxidants will act in the same way as antioxidants in foods and help prevent cancer. But research has shown that taking supplements to reduce the risk of cancer may not be effective. This is because the specific components that provide the protective effect are not clearly known, so can’t be replicated as supplements. That’s why Cancer Council recommends people eat a nutritious diet, including a variety of whole, fresh vegetables and fruits. And while antioxidants may be beneficial in healthy people because they attack active chemicals called free radicals which can damage DNA, cancer treatments such as chemotherapy and radiotherapy actually use free radicals to kill tumour cells. Scientific studies have suggested antioxidants may have the opposite effect in people undergoing cancer treatment. Some people having cancer treatment may be advised to take supplements because of the side-effects of their treatment or other health issues or confirmed nutritional deficiency. But for others, certain supplements are unlikely to be helpful and may be harmful. If you are having cancer treatment, talk to your doctor about any supplements or other medications you are taking or thinking about taking.