β-Carotene: Radical Reactions and Cancer Associations-Leading Down a Rabbit Hole?

Approximately 600 carotenoids have been identified with about 100 finding their way into foodstuffs consumed by humans [1]. These pigments are widely distributed as naturally occurring constituents of fruits and vegetables. They are often added to human foodstuffs in order to achieve acceptable food coloration as they strongly absorb light in the region of 400-500 nm and are colored red, orange, and yellow. Chemically these pigments are tetraterpenoids consisting of eight isoprenoid residues. Carotenoids serve in a protective role to photosensitization by endogenous photosensitizers such as the porphyrin-containing photosynthetic pigments and in the human genetic disorder Erythropoietic protoporphyria. β-carotene is an important micronutrient for human health as it is a non-toxic precursor for the synthesis of vitamin A. Its role in affecting a reduction in cancer incidence is in question.