Hormesis and health: a little of what you fancy may be good for you.

The term hormesis refers to beneficial effects from low doses of potentially harmful substances. Although there are many laboratory examples of this phenomenon, it remains controversial and has never become widely accepted by the health community. This review goes beyond the laboratory and describes many clinical and common sense, real-world examples of hormesis that often go unrecognized. Many vitamins and minerals are essential for life at low doses but toxic at higher ones. Similarly, exercise, caloric restriction, and alcohol consumption are examples of processes that are harmful in the extreme but beneficial in moderation. This review also highlights possible reasons why acceptance of the hormetic paradigm has lagged. These include high-dose toxicologic testing that precludes the demonstration of low-level effects and the threat posed by hormesis to the currently accepted precautionary principle, which assumes that any dose of a chemical is potentially harmful.