British Journal of Nutrition

Full Papers

Phytanic acid: measurement of plasma concentrations by gas–liquid chromatography–mass spectrometry analysis and associations with diet and other plasma fatty acids

Naomi E. Allena1, Philip B. Gracea2, Annette Ginna2, Ruth C. Travisa1, Andrew W. Roddama1, Paul N. Applebya1 and Timothy Keya1 c1

a1 Cancer Epidemiology Unit, University of Oxford, Richard Doll Building, Roosevelt Drive, Oxford OX3 7LF, UK

a2 HFL Limited, Newmarket Road, Fordham, Cambs CB7 5WW, UK


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 α-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 μmol/l; P < 0·0001) and a 47 % higher mean concentration than the vegetarians (5·77 v. 3·93 μmol/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.

(Received March 07 2007)

(Revised July 05 2007)

(Accepted July 20 2007)


c1 Corresponding author: Professor Timothy Key, fax +44 1865 289610, email


Abbreviations: AMACR, α-methylacyl-coenzyme A racemase; EPIC-Oxford, Oxford component of the European Prospective Investigation into Cancer and Nutrition; QC, quality control