Which vitamins are good for the male urethra?

None: That i know of. Most men of your age will benefit from vitamin d, specially if they live in northern places & use sun block. Not for urethra, but for general health. There is little scientific evidence of any other vitamins being good for anything. Healthy diet with lots of fresh fruit & vegetables, low in sugar & carbs & modest with red meat is better than all the vitamins in the world.