Within the Medical Sciences exist many paradigms because scientific investigation characteristically changes the knowledge continuously. Since the early development and adaptation of eukaryotic cells to aerobic life a side effect of this kind of metabolism has been the production of reactive oxygen species. One of the most important and recognized scientific theories is the free radical theory of aging which sustain that aging is produced by oxidative stress caused by free radicals produced during the oxidative phosphorylation at the mitochondria. It is proposed that a metabolic state in which the fuel is not enough for energy production could cause a lower free radical production and a stop the aging. It has been demonstrated that calorie restriction in invertebrates and small species halt the aging process. Considering this concept one of the most important paradox is proposed, the oxygen paradox: we need the oxygen to turn the glucose into energy, but a side effect of this oxygen metabolism is the normal aging. In this manuscript we describe and analyze important concepts about the evolutive adaptation to the aerobic environment in our planet and one of the most important consequences for the humans: the aging process and the possibility of dietary and pharmacologically manipulation.

Free radicals; mitochondria; aging; calorie restriction