title: Phytanic acid: measurement of plasma concentrations by gas-liquid chromatography-mass spectrometry analysis and associations with diet and other plasma fatty acids.
abstract: Epidemiological data suggest that a diet rich in animal foods may be associated with an increased risk of several cancers, including cancers of the prostate, colorectum and breast, but the possible mechanism is unclear. It is hypothesised that phytanic acid, a C20 branched-chain fatty acid found predominantly in foods from ruminant animals, may be involved in early cancer development because it has been shown to up regulate activity of alpha-methylacyl-coenzyme A racemase, an enzyme commonly found to be over-expressed in tumour cells compared with normal tissue. However, little is known about the distribution of plasma phytanic acid concentrations or its dietary determinants in the general population. The primary aim of the present cross-sectional study was to determine circulating phytanic acid concentrations among ninety-six meat-eating, lacto-ovo-vegetarian and vegan women, aged 20-69 years, recruited into the Oxford component of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Meat-eaters had, on average, a 6.7-fold higher geometric mean plasma phytanic acid concentration than the vegans (5.77 v. 0.86 micromol/l; P < 0.0001) and a 47 % higher mean concentration than the vegetarians (5.77 v. 3.93 micromol/l; P = 0.016). The strongest determinant of plasma phytanic acid concentration appeared to be dairy fat intake (r 0.68; P < 0.0001); phytanic acid levels were not associated with age or other lifestyle factors. These data show that a diet high in fat from dairy products is associated with increased plasma phytanic acid concentration, which may play a role in cancer development.
authors.affiliation: Cancer Epidemiology Unit, University of Oxford, Richard Doll Building, Roosevelt Drive, Oxford OX3 7LF, UK.
authors.forename: Naomi E
authors.initials: NE
authors.lastname: Allen
authors.forename: Philip B
authors.initials: PB
authors.lastname: Grace
authors.forename: Annette
authors.initials: A
authors.lastname: Ginn
authors.forename: Ruth C
authors.initials: RC
authors.lastname: Travis
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Roddam
authors.forename: Paul N
authors.initials: PN
authors.lastname: Appleby
authors.forename: Timothy
authors.initials: T
authors.lastname: Key
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood; D000886:Anthropometry; D003430:Cross-Sectional Studies; D003611:Dairy Products / Q000706:statistics & numerical data; D004032:Diet / Q000706:statistics & numerical data*; D014676:Diet, Vegetarian / Q000706:statistics & numerical data; D005227:Fatty Acids / Q000097:blood*; D005247:Feeding Behavior; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D010831:Phytanic Acid / Q000097:blood*
chemical_list: D005227:Fatty Acids; D010831:Phytanic Acid; C117025:pentadecanoic acid; C013102:margaric acid