Vegetarian diets are becoming increasingly popular, yet the assessment of pancreatic function tests in vegetarians is sparse. Chronic pancreatitis and exocrine pancreatic insufficiency are more common than previously thought. Therefore, a means of accurately measuring pancreatic function in vegetarian subjects is needed. Direct pancreatic function tests, such as the secretin-cholecystokinin-test (SCT), have the highest sensitivity and specificity. However, they have some major disadvantages, including invasiveness and availability, which make them unsuited for routine use (1). Among the indirect tests, the measurement of fecal enzyme concentrations/activities is the easiest. Fecal elastase-1 is probably the most sensitive and specific of the indirect tests (2). However, there are no data regarding the specificity of these tests in vegetarians. In the current study we investigated the impact of vegetarian diet on the specificity of fecal tests of pancreatic function.
MATERIALS AND METHODS
Ninety-six healthy vegetarian (V) and 105 healthy nonegetarian (NV) subjects aged 5 to 45 years were included in the study. Vegetarians were divided into two subgroups: vegans (diet based exclusively on fruits and vegetables) and others (lactovegetarians and lactoovovegetarians). The duration of the diet ranged from 1 to 12 years.
In all subjects, fecal elastase-1 (E1) concentration and fecal chymotrypsin (ChT) activity were measured. E1 was measured by an enzyme-linked immunosorbent assay (ScheBo·Biotech, Giessen, Germany), and ChT was measured by colorimetric method (Roche Diagnostics GmbH, Mannheim, Germany) (2). For further analysis, the mean value from three nonrelated measurements was taken. In addition, in 20 vegetarians, daily output of fecal enzymes was assessed and compared to that in 20 healthy subjects. All stools were weighed and the fecal elastase-1 activity/fecal chymotrypsin concentration was analyzed in three unrelated samples from every stool. Fecal enzyme output was defined as a mean of a 72-hour collection period.
The statistical differences between nonpaired data of vegetarian and nonvegetarian subjects were calculated with the use of the Whitney-Mann test. The levels of significance was set at P < 0.05.
E1 concentrations ranged from 65 to 1,568 μg/g in vegetarians and from 238 to 1,614 μg/g in healthy nonvegetarians. ChT activities ranged from 2.6 to 52.4 U/g in vegetarians and from 6.4 to 50.1 U/g in nonvegetarians. Both E1 concentrations and ChT activities were significantly lower in vegetarians than in nonvegetarian subjects (P < 0.001). A decreased specificity for both tests was found in vegetarians (Table 1). E1 concentrations and ChT activities were lower in vegans than in the other vegetarians, but the difference was not statistically significant. No correlation between fecal enzyme concentrations and duration of the diet in vegetarians was found.
Daily fecal output of elastase-1 ranged from 7,411 to 189,933 μg/d in vegetarians and from 8,080 to 194,800 μg/d healthy nonvegetarians. Daily fecal output of chymotrypsin ranged from 222.0 to 3,677.3 U/g in vegetarians and from 331.0 to 3,876.8 U/g in nonvegetarians. Fecal enzyme output in vegetarians, although lower, was not statistically different from that observed in nonvegetarians. However, stool weight was significantly higher (P < 0.015) in vegetarians (range, 40.2–232.0 g/d) than in nonvegetarians (range, 20.0–223.3 g/d) (Table 1).
In this study, we have shown that a vegetarian diet can alter the assessment of exocrine pancreatic function. In animal models, adaptation of pancreatic exocrine function to different diets (low- and high-fat, low- and high-protein, etc.) has been described (3). However, there are few consistent data in humans on this question (4–6). Boivin et al. (5) reported that diets with a high proportion of calories as carbohydrate for 2 weeks are associated with lower interdigestive and postprandial pancreatic secretion than are diets with high fat content. In contrast, Liehr et al. (7) showed that an increase in dietary carbohydrate does not provoke an adaptative response in stimulated secretion rates of amylase, trypsin, and chymotrypsin in humans. No studies have been conducted on the effect of the vegetarian diet on pancreatic function measured by direct or by indirect tests. Because a vegetarian diet lacks the substrate for pancreatic elastase-1 as an enzyme, one might expect a reduced secretion and therefore a limited value of this test in vegetarians. However, combined measurements of E1 concentrations and ChT activities provided information that the influence of vegetarian diets on exocrine pancreatic function in healthy subjects is not limited to E1. The reduction of ChT activity may be related to the reduction in the activity of pancreatic enzymes by dietary fiber (colorimetric method). Another possible explanation is that decreased protein intake, often characteristic of vegetarian diets, may reduce pancreatic enzyme secretion. However, the increased fiber intake might produce the increased amount of stool. The same amount of enzymes in a larger volume of stool might lead to the “dilution effect,” which has been shown by the results of this study. In conclusion, the specificity of fecal tests in the assessment of exocrine pancreatic function in vegetarians is reduced.
1. Walkowiak J, Cichy W, Herzig KH. Comparison of fecal elastase-1 determination with the secretin-cholecystokinin test in patients with cystic fibrosis. Scand J Gastroenterol 1999; 34:202–7.
2. Walkowiak J, Herzig KH, Strzykala K, et al. Fecal elastase-1 is superior to fecal chymotrypsin in the assessment of pancreatic involvement in cystic fibrosis. Pediatrics 2002; 110:E1–7.
3. Chowdhurry P, Nishikawa M, Blevins Jr, GW et al. Response of rat exocrine pancreas to high-fat and high-carbohydrate diets. Proc Soc Exp Biol Med 2000; 223:310–5.
4. Emde C, Liehr RM, Gregor M, et al. Lack of adaptive changes in human pancreatic amylase and lipase secretion in response to high-carbohydrate, low-fat diet applied by a 10-day continuous intraduodenal infusion. Dig Dis Sci 1985; 30:204–10.
5. Boivin M, Lanspa SJ, Zinsmeister AR, et al. Are diets associated with different rates of human interdigestive and postprandial pancreatic enzyme secretion? Gastroenterology 1990; 99:1763–71.
6. Pitchumoni CS, Scheele GA. Interdependence of nutrition and exocrine pancreatic function. In: Go VLW, et al., eds. The Pancreas; Biology, Pathobiology and Diseases.
2nd ed. New York: Raven Press; 1993:449–73.
7. Liehr RM, Herrmann ME, Emde C, et al. High amount of dietary carbohydrate does not cause an adaptational increase of stimulated human pancreatic amylase secretion. Int J Pancreatol 1989; 4: 419–30.