Discontinuous distribution of N-oxidation of dietary-derived trimethylamine in a British population

Xenobiotica. 1996 Sep;26(9):957-61. doi: 10.3109/00498259609052497.


1. Whilst the majority of individuals within a British white population are able to convert > 90% of their dietary-derived trimethylamine to its N-oxide, outliers exist who show varying degrees of decreased metabolism. Such individuals, excrete unoxidized trimethylamine in their urine and, if N-oxidation is sufficiently low, may experience malodour problems (Fish-Odour syndrome). 2. Such observations have now been extended to a much larger group (n = 421; 221 males) of British white volunteers recruited from staff and students of Imperial College Medical School at St. Mary's, London. Each subject collected a 0-24-h urine sample, which was subsequently analysed for total trimethylamine and trimethylamine N-oxide content. 3. Sixteen subjects (3.8% population; seven male, nine female) excreted < 90% of their total trimethylamine output as N-oxide. All six subjects who excreted < 80% as N-oxide (indicative of potential heterozygous status for deficient N-oxidation-fish odour syndrome) were female.

MeSH terms

  • Adult
  • Diet*
  • Female
  • Humans
  • Male
  • Metabolism, Inborn Errors / urine
  • Methylamines / pharmacokinetics*
  • Methylamines / urine
  • Middle Aged
  • Odorants
  • Oxidation-Reduction
  • United Kingdom


  • Methylamines
  • trimethyloxamine
  • trimethylamine