A mitochondria is like a tiny furnace contained in each cell in the body. Mitochondria generate energy inside each cell by burning food in the presence of oxygen. This is why cells that are fully oxygenated have a higher level of energy. But again, oxygen can be both friend and foe. This firing process ends up subjecting the mitochondria themselves to high levels of free radical damage. As we age, mitochondria become so damaged by these free radicals that they lose their ability to function efficiently.