A Swedish study found that women who regularly took multivitamins were 19% more likely to develop a breast cancer than those who did not take multivitamins1. 35,329 women aged 49 to 83 years old took part in that study and were followed up for 10 years. The research found that women who had taken multivitamins for three years or more and those who took seven or more multivitamins a week were at increased risk of breast cancer compared to non-users.
At present, the link between multivitamin use and breast cancer risk remains uncertain and further study is warranted to clarify that. If so, it is also important to identify which component(s) of the multivitamin supplements are responsible.
Most of us should be able to meet our recommended daily intake of vitamins and minerals from a balanced diet, rich in fruits, vegetables and other plant-based foods. The World Cancer Research Funds recommends not using supplements to protect cancers because scientists cannot be certain that we get the same benefit if we consume nutrients in this form2. Research also shows that taking high doses of some supplements could be harmful to our health. However, some groups of people may benefit from taking supplements. For instance, women who could become pregnant are advised to take a folic acid supplement from before conception until the 12th week of pregnancy in a view to preventing the risk of developing neural tube defects.
- Larsson SC, Åkesson A, Bergkvist L and Wolk A. Multivitamin use and breast cancer incidence in a prospective cohort of Swedish women. American Journal of Clinical Nutrition, 2010 May;91(5):1268-72