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 a-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 mmol/l; P, 0·0001) and a 47 % higher mean concentration than the vegetarians (5·77 v. 3·93 mmol/l; P¼ 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.

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Summary The purpose of the present report was to estimate the population parameters of cortisol concentrations in urine, an endogenous hormone used as a ‘doping’ agent and for which an international threshold (1.0 μg/ml) has been proposed. Two data bases (French and UK) corresponding to 112 and 142 samples, respectively were considered. Urine was collected under specific post competition conditions. Cortisol concentrations were obtained by validated methods (HPLC for the French samples, and GC‐MS for UK samples). No difference was observed between the 2 data sets and statistical analyses were carried out on the two merged flies. The overall geometric mean cortisol concentration was 48 ng/ml. Distribution was not Gaussian. A log‐normal distribution was not rejected (for P>0.05). Using the log‐normal distribution, it was calculated that the probability of exceeding a cortisol concentration in urine of 1.0 μg/ml was 1.1 times 10−4. It was concluded that the actual international threshold is specific i.e. robust with regard to the risk of erroneously declaring an unmedicated horse as positive.

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