Your body requires all different kinds of vitamins to function properly and to have adequate energy. One of the most important vitamins for energy are the B vitamins. B vitamins help metabolize carbohydrates into energy, which is the main source of fuel for your body and your brain. A lack of B vitamins can lead to low energy, depression, irritability, mood imbalances, and poor memory. A few good natural sources of vitamin B are liver, organic chicken and beef, whole grains, bananas, avocados, walnuts, and sunflower seeds. If you have a hard time getting your B vitamins from natural food sources, you may want to consider a B vitamin supplement. That way you can help ensure your body is getting the energy it needs.