Q. I take a multivitamin after breakfast. I notice that my urine turns bright yellow for several hours afterwards. What causes this change in color and is it dangerous?
A. Riboflavin (vitamin B2) can color urine an almost fluorescent yellow. It is not dangerous.
The bigger question is whether you need to take a multivitamin. This has become quite controversial, with several studies suggesting that vitamin supplements are not associated with a reduced risk of heart disease over the long term (Journal of the American Medical Association, Nov. 7, 2012). It appears, however, that a multivitamin may modestly lower the risk of cancer in men (Journal of the American Medical Association, online Oct. 17, 2012).
If you’d like to learn more about the arguments for and against vitamin supplements, you may want to listen to our radio show #876, The Great Vitamin Debate.