Human urine was collected over a 24 h period after the consumption of 250 mL of (i) water, (ii) orange juice, and (iii) orange juice plus 150 mL of full fat natural yoghurt. The orange juice contained 168 micromol of hesperetin-7-O-rutinoside and 18 micromol of naringenin-7-O-rutinoside. GC-MS analysis of the urine identified nine phenolic acids, five of which, 3-hydroxyphenylacetic acid, 3-hydroxyphenylhydracrylic acid, dihydroferulic acid, 3-methoxy-4-hydroxyphenylhydracrylic acid and 3-hydroxyhippuric acid, were associated with orange juice consumption indicating that they were derived from colonic catabolism of hesperetin-7-O-rutinoside. The overall 0-24 h excretion of the five phenolic acids was 6.7 +/- 1.8 micromol after drinking water and this increased significantly (p < 0.05) to 62 +/- 18 micromol, equivalent to 37% of the ingested flavanones, following orange juice consumption. When the orange juice was ingested with yoghurt excretion fell back markedly to 9.3 +/- 4.4 micromol. This was not due to a difference in mouth to caecum transit time, as measured with breath hydrogen production, though possibly there may have been a slowing of the bulk of the meal reaching the large intestine which may then have altered the catabolism of the flavanones to phenolic acids by the colonic microbiota.