AGEING

MITOCHONDRIAL DECLINE AND AGEING

The free radical theory of ageing is based on the idea that our cells and DNA (the latter containing the code for proper cell division and replication) eventually become irreversibly damaged by the onslaught of highly-reactive chemical species called ‘free radicals’. These transient species are generated unavoidably as a by-product of aerobic (oxygen) metabolism. In other words, while oxygen provides us with the energy for life, it’s also responsible for generating highly damaging chemical species that cause biochemical havoc within the cells of our bodies. The mitochondrial decline theory of ageing takes this process one step further. Mitochondria are the energy-producing furnaces in the body, whose job is to make adenosine triphosphate (ATP), the energy currency of life, by burning fuel in the presence of oxygen. But this process inevitably leaves the mitochondria themselves subject to very high levels of damaging free radical attack by reactive oxygen species. Mitochondria lack many of the defense systems found in other parts of the body, so they decline in number and efficiency with age, leading to a corresponding decline in ATP production. Reduced ATP means less energy to fuel the vital life-sustaining processes of the body, which can result in the onset of a number of disease states and processes.