No, you do not need to take any supplements for cycling, but you may find some helpful for performance. Several supplements have been studied for their performance-enhancing abilities, including tart cherry juice, turmeric, caffeine, creatine, sodium bicarbonate, beta-alanine, and magnesium. More generic supplements such as protein powder, electrolyte mix-ins, and multi-vitamins can also be beneficial for cyclists in certain instances.
Supplements should be tailored to individual goals, needs, age, and activity level, and taking too much of a supplement, or the wrong supplement, can be detrimental to cycling performance as well as your health. Read more about supplements for cyclists here.