The contribution of the large intestine to blood acetate in man.

1. To test the hypothesis that the colon contributes significantly to venous plasma acetate concentrations, experiments were carried out in healthy volunteers and ileostomy patients. 2. Fasting plasma acetate levels were measured in 10 ileostomy patients and compared with those in 21 control subjects. Values in ileostomy patients (21.3 +/- 0.8 mumol/l) were significantly lower than in control subjects (48.0 +/- 4.2 mumol/l). 3. Plasma acetate concentration was estimated in eight healthy volunteers during 108 h of continuous fasting. Acetate concentrations rose significantly from 12 h (43.9 +/- 4.4 mumol/l) to 108 h of starvation (114.0 +/- 15.6 mumol/l) and fell back to normal fasting values on refeeding and another 12 h fast (44.3 +/- 4.7 mumol/l). 4. When colonic fermentation was stimulated after oral ingestion of 10 g of lactulose, the plasma acetate concentration increased significantly (from 44.0 +/- 7.4 to 114.4 +/- 16.2 mumol/l) in seven healthy control subjects. This rise was not affected by concomitant dosage of metronidazole. 5. These data suggest that there are at least two major sources of acetate in man, an endogenous source and the colon which probably becomes more important when fermentation of carbohydrate is occurring.