That's because it takes the body one to four hours to digest food. So foods eaten just before a competition are in your stomach when you compete. Most of the energy used in competition or practice comes from foods eaten days before and event that have been stored in your muscles. Vitamin supplements give you more energy. No vitamin provides energy.
Some vitamins help the body use energy.
Megadoses of vitamins won't give you extra energy or improve your performance. Extra vitamins that your body does not need are eliminated in your urine. Fat soluble vitamins, A, D, E, and K in excess are stored in your body. Too much of these vitamins can be poisonous. Athletic success is not a miracle.