[Excretion of Phenol and P-Cresol in the Urine in Fasting Obese Individuals and in Persons Treated with Total Enteral Nutrition].

In the literature it is maintained that phenol and p-cresol are produced in humans in the gut by bacteria from dietary protein. Both substances are absorbed from the small intestine and excreted in the urine. If the urinary output of phenol and p-cresol depends really on the dietary protein intake it should decline to zero values during fasting and correlate with the protein supply into the gut. The objective of the present work was therefore to investigate the urinary phenol and p-cresol excretion in fasting obese subjects (21 fasting subjects, 7 subjects with modified fasts--Nutramine R-350) and in subjects treated by complete enteral nutrition by a nasojejunal tube (8 patients with Crohn's disease, 8 with another disease of the gastrointestinal tract). Phenol and p-cresol in 24-hour urine specimens were assessed by gas chromatography in all four groups always on the 1st, 7th and 14th day. In fasting obese subjects the phenol and p-cresol values did not decline (the difference of values from the assumed zero value is significant z = 0.000055). There was no difference between patients with a complete and modified fast. The phenol and p-cresol values did not correlate mutually, nor with the protein intake, nitrogen balance and cumulated nitrogen balance. There are great individual differences in the urinary phenol and p-cresol excretion and it does not depend on the oral dietary protein intake, as hitherto assumed. It has most probably more complex causes and the decisive factor seems to be the metabolic activity of the intestinal bacterial microflora.