Phytanic acid arises through ruminant metabolism of chlorophyll and enters the human diet as a constituent of dairy products (Baxter 1968). It can act as an agonist for PPAR and other nuclear hormone receptors, but its normal role in human physiology, if any, is unclear. It is catabolized via a five-step alpha-oxidation reaction sequence that yields pristanoyl-CoA, which is turn is a substrate for beta-oxidation. These reactions take place in the peroxisomal matrix and their failure is associated with Refsum disease (Wanders et al. 2003).