Effect of an acute protein load on the creatinine clearance in healthy vegetarians

In normal man an acute protein load increases the glomerular filtration rate (GFR) significantly, which seems to represent a renal functional reserve. Healthy vegetarians are known to have a statistically reduced baseline GFR. We performed three creatinine clearance studies (24-h study design) on each of nine healthy vegetarian subjects. The first clearance was measured as baseline, the second one was done on day 2 after an oral protein load of 100 g vegetarian protein (1.2-2.0 g/kg body wt.), respectively, ingested within half an hour. The third clearance, serving as a control, was done on day 14. All subjects had their normal vegetarian meals during the study. All vegetarians had at all times a normal serum creatinine level. The mean baseline creatinine clearance was 65.4 +/- 33.3 ml/min. 1.73 m2. In five of nine vegetarians we found a significant increase of the creatinine clearance after the protein load of 66.0% (mean) and a decrease to the baseline values, respectively, when the control clearance was measured. The remaining four vegetarians did not increase their creatinine clearance immediately after the protein challenge and their control clearances were found to be significantly reduced (-40.2%) compared to the individual baseline.