Human biology is under enormous oxidative stress.
We have polluted this world with chemicals and heavy metals and damaged the ozone protective layer of our atmosphere. Thus, free radicals leading to oxidative stress cause human illness. One hundred years ago, the major threats to the survival of our ancestors were caused by infectious agents. Today, the major threats to our survival are imposed upon us by synthetic chemicals, toxic heavy metals, and the stress of modern living. The medical thought of the 19th century was dominated by the microbial threat.