Lipid oxidation is one of the main chemical degradations occurring in biological systems and leads to the
formation of compounds that are related to aging and various chronic and degenerative diseases. The
extent of oxidation will depend on the presence of antioxidants/pro-oxidants, the unsaturation degree of
fatty acids, and environmental conditions. Lipid oxidation can also affect other molecules that have double
bonds in their chemical structures, such as cholesterol. Cholesterol oxidation products (COPs) have been
studied in depth, because of their negative and controversial biological effects. The formation of COPs can
be particularly favored in the presence of light and photosensitizers, since they generate excited singlet
oxygen that rapidly reacts with the double bond by a non radical mechanism and without any induction
period. The present review intends to provide an overall and critical picture of cholesterol photosensitized
oxidation in food and biological systems, and its possible impact on human health and well-being.