The free radical theory of aging argues that free radicals produced by the mitochondria are responsible for the damage that affects all biological tissues and leads to the aging phenotype. High olive oil intake is related to lower mitochondrial oxidative stress, including that which happens during aging. The degree of fatty acid unsaturation of mammalian tissues is also negatively correlated with greater longevity, and olive oil leads to less polyunsaturated biological membranes. Finally, monounsaturated fatty acids (such as those of olive oil) have been associated with greater longevity and a high degree of protection against age-related cognitive decline in humans