This question is about Nutrition and Cycling
Most cyclists do not need to take vitamins, however, some cyclists may benefit from vitamin and mineral supplements if they are deficient in a nutrient or fall short of the recommended daily intake.
For example, vitamin D
Eating a well-balanced diet with fruits, vegetables, whole grains, and protein, should largely provide the nutrients you need to support cycling performance and general health. If you think you may be deficient in a certain nutrient, talk to your doctor about checking your levels. More information on supplements for biomarkers can be found here