Bilirubin is the major catabolic product of heme degradation. It has long been regarded as an unimportant waste product.
However, within the last twenty-five years, it has been demonstrated to play a very important role in maintaining the body's redox equilibrium. Disturbances of this equilibrium - increased oxidative stress - are currently considered one of the major risk factors for the development of non-communicable diseases.
Although the exact mechanism is not known, a number of human studies have proved a reduced incidence of a number of (especially cardiovascular but also cancer) diseases in individuals with mildly elevated bilirubin concentrations.