Exercise as prevention: do the health benefits derive in part from lower iron levels?

The mechanism by which exercise, a key component of modern preventative medicine, protects man from strikingly different diseases such as heart disease and cancer, is largely a mystery. It is proposed that exercise-induced reductions in iron levels, either through iron loss or enhanced iron storage, could be responsible for some of the beneficial effects. Possible roles for iron in coronary artery disease and cancer have recently emerged, particularly as a catalyst for oxygen free radical-induced tissue damage. The iron hypothesis is consistent with the graded reductions in mortality observed as a function of fitness level, and it is the first unified mechanism which can explain the reductions in both heart disease and cancer. If confirmed, preventative medicine in the future will need to include close monitoring of iron levels and, possibly, occasional blood donation for those with moderately high iron stores.