What all the above posters have said is correct. However, when i went through chronic tiredness, lack of energy and no motivation, it was ALL due to the massive build up of candida in my stomach. I was eating right, but my body wasn't absorbing the vitamins from the food and my liver wasn't working properly. I had been to a series of doctors and had blood tests and took vitamins and nobody knew what was wrong with me. Then by chance a family friend mentioned that she had her son and herself tested for allergies by a doctor and he had found they both suffered from an overgrowth of candida.The candida in her son casued him to by very hyperactive in class and suffered from low grades. After treatment his teachers couldn't believe he was the same child, who now behaved and was getting top marks in class.
I went to see this doctor and was placed on a special diet for 3 weeks and told to take acidophillous, multivitamins and oral medication called nicostatin (sp?). After only two weeks i felt like superwoman and couldn't believe the energy i had and how alive i felt.