The elimination of meat from the diet selectively decreases pancreatic
Jaroslaw Walkowiak1*, Lidia Wadolowska2, Anna Szaflarska-Poplawska3, Aleksandra Lisowska1,
Alina Bugajewska1and Juliusz Przyslawski4
1Department of Gastroenterology & Metabolism, Poznan University of Medical Sciences, Poznan, Poland
2Institute of Human Nutrition, University of Warmia and Mazury, Olsztyn, Poland
3Collegium Medicum, Mikolaj Kopernik University, Torun, Poland
4Department of Human Nutrition, Poznan University of Medical Sciences, Poznan, Poland
(Received 6 June 2006 – Revised 4 December 2006 – Accepted 10 January 2007)
Since the vegetarian diet lacks the substrate for pancreatic elastase-1 as an enzyme, a decreased secretion of this enzyme could be expected. We
aimed therefore to assess the changes of exocrine pancreatic secretion in a prospective way in a group of healthy omnivores who modified their
diet by abstaining from meat for 1 month. Twenty healthy omnivores (fourteen females and six males) were used in the study. The nutrient intake
was assessed for 7d before commencing the study (omnivore diet) and after 1 month of dietary modification (modified diet; meat excluded). Simi-
larly, the faecal output of pancreatic enzymes (elastase-1, chymotrypsin and lipase) was assessed before and 1 month after the period of dietary
modification. Statistical differences between two points of the assessment (paired data) were calculated with the use of the Wilcoxon rank test. The
relationship between the changes of faecal enzyme output and the changes in nutrient intake was assessed using multiple regression analysis. The
dietary changes resulted in statistically significant decrease of faecal elastase-1 output (P,0·05), whereas for chymotrypsin and lipase no changes
were observed. No significant change in stool weight was recorded. No statistically significant correlation between changes in energy and nutrient
consumption and changes in faecal output of pancreatic enzymes has been found. It was concluded that the exclusion of meat from the diet for a
1-month period results in significant changes in pancreatic secretion with a selective decrease of elastase-1 output. However, the underlying factor
Exocrine pancreatic secretion: Faecal enzymes: Nutrition: Meat: Lactoovovegetarian diet
The effect of a vegetarian diet on exocrine pancreatic
secretion creates an interesting opportunity for the assessment
of pancreatic adaptation to human nutrition. In a group of
twenty lactoovovegetarians pancreatic exocrine secretion
was assessed and compared to that of thirty-two non-veg-
etarian subjects (Walkowiak et al. 2006). Daily faecal elas-
tase-1 (FE1) and chymotrypsin (FCht) outputs in vegetarians
and omnivores did not differ significantly. Since a vegetarian
diet lacks the substrate for pancreatic elastase-1 as an enzyme,
a decreased secretion of this enzyme could be expected. How-
ever, such a phenomenon was not reported in the study (Walk-
owiak et al. 2006). Neither was any correlation between
nutrient intake and pancreatic enzyme secretion stated. The
limitation of the study was related to a cross-sectional
model of the assessment (non-paired data). The significant
differences in the intake of several nutrients between lactoovo-
vegetarians and non-vegetarian subjects could also influence
The vegetarian diet is becoming increasingly popular, yet
there is no information on adaptation of pancreatic secretion
to this dietary modification. Therefore, its potential influence
should be elucidated. In the present study we aimed to
assess the changes of exocrine pancreatic secretion in a pro-
spective way in a group of healthy omnivores who modified
the diet by abstaining from meat for 1month.
Materials and methods
The study lasted for 5 weeks. Healthy omnivore volunteers
abstained from all products containing meat and replaced
them with lactoovovegetarian products for the period of the
study. The nutrient intake was assessed for 7d before entering
the study (omnivore diet) and after 1 month of dietary modi-
fication (modified diet; meat excluded). Similarly, the faecal
output of pancreatic enzymes (FE1, FCht and faecal lipase
(FLP)) was assessed before and 1 month after the period of
dietary modification. Inclusion criteria were being an omni-
vore, having good general and nutritional status, and a willing-
ness to participate in the study. Exclusion criteria were any
history of gastrointestinal or systemic disease, any acute
*Corresponding author: Professor Jaroslaw Walkowiak, fax 48 61 8483362, email firstname.lastname@example.org
Abbreviations: FE1, faecal elastase-1; FCht, faecal chymotrypsin; FLP, faecal lipase.
British Journal of Nutrition (2007), 98, 154–158
q The Authors 2007
disease within 1 month prior to or during the study, and dis-
continuation of dietary modification during the study.
The sample size was established according to Altman’s nor-
mogram (Petrie & Sabin, 2005). There were no drop-outs
during the study. The volunteers were selected from students
and young workers of the University of Warmia and
Mazury. Exclusively highly motivated and enthusiastic sub-
jects were entered in the study. Volunteers received detailed
information on meat-containing and meat-free products, as
well as several examples of different meals. The diet compli-
ance was checked three times per week.
Twenty healthy omnivores (fourteen females and six males)
aged 22 to 26 years (mean age 24·1(SD 0·8) years) were
included into the study. Their BMI values were in the range
of 18·0 to 29·3kg/m2(mean 21·6 (SD 2·9) kg/m2).
The assessment of nutrient intake (all available macro- and
micronutrients) was based on the records of 7-d weighed
rations. The records (with use of scales with an approximation
of 0·1g) were collected at home. Subjects were given both oral
and written instructions. The diet records were reviewed and
clarified (JP). The obtained data were analysed using our
own, previously created, computer database (Microsoft
Access 7.0; J.P.) prepared on the basis of tables for the com-
position and nutritional value of food products (Kunachowicz
et al. 2005). The degree to which the recommended intake was
met was considered in relation to values given by the National
Institute of Food and Nutrition in Warsaw (Ziemlan ´ski et al.
1994). Physical activity was assessed by a 7-d recall (Ziem-
lan ´ski & Bułak-Jachymczyk, 2001). All subjects were found
to have moderate activity which did not differ between the
two periods of the study.
Faecal enzymes were determined in three independent
samples of every stool. For further analysis the mean value
was taken. FE1 concentration (the test based on monoclonal
antibodies) and FLP activity were measured by use of an
immunoenzymatic method (ELISA) (Scheefers-Borchel et al.
1992, Walkowiak et al. 2004a), whereas FChT activity
was measured using a colorimetric method (Brown et al.
1988). Faecal enzyme output was calculated according to
the following formula:
FEO ¼FE1£ SW1þ ··· þ FEn£ SWn
where FEO is faecal enzyme output, FEnis faecal enzyme
concentration/activity in subsequent (n) stool and SWn is
stool weight of subsequent (n) stool.
The protocol of the investigation was approved by the Ethi-
cal Committee of the Poznan University of Medical Sciences,
Statistical differences in nutrient intake, stool weight and
faecal enzyme output between two points of the assessment
(paired data) were calculated with the use of the Wilcoxon
rank test. The relationship between the changes of faecal
enzyme output and the changes in nutrient intake (all available
macro- and micronutrients) was assessed using multiple
If not stated otherwise, values are expressed as means with
their standard deviation. The level of significance was set at
The daily output of FE1, FCht and FLP on an omnivore diet
and on the modified diet are given in Table 1. Dietary changes
resulted in a statistically significant decrease of FE1 output
(P,0·05), whereas for FCht and FLP no changes were
observed. In addition, no significant changes in stool weight
were recorded (100·9 (SD 53·1) v. 102·2 (SD 63·4) g/day).
The comprehensive nutritional data are presented in Table 2.
No significant changes in the consumption of energy, total
protein, fibre or SFA were found. However, a significant
increase of plant protein (P,0·003) and carbohydrate
(P,0·006), fat (P,0·006), Se (P,0·003), MUFA (P,0·01)
and PUFA (P,0·02) were found.
No statistically significant correlation between relative and
non-relative changes in energy and nutrient consumption and
changes in faecal output of pancreatic enzymes was found.
Pancreatic adaptation occurs in response to different dietary
nutrients. The assessment of the effect of a vegetarian diet
on exocrine pancreatic secretion therefore creates an interest-
ing opportunity for the evaluation of this adaptive process.
Faecal tests are the most sensitive and specific indirect tests
for the assessment of pancreatic function and secretion (Walk-
owiak et al. 2005). As reported for healthy subjects (Stein et al.
1996) and patients with severe exocrine pancreatic deficiency
(Walkowiak et al. 1999), FE1 concentrations correlate signifi-
cantly with parameters of direct tests that are the gold standard
in the assessment of pancreatic function. Also, the vegetarian
diet lacks the substrate for pancreatic elastase-1 as an enzyme
and decreased secretion of elastase-1 in vegetarians could be
expected (Walkowiak et al. 2004b). Therefore, we used an
FE1 test for the assessment of changes in exocrine pancreatic
secretion. On the other hand, a vegetarian diet potentially
gives the stimulation for chymotrypsin secretion. Therefore
Table 1. Daily faecal elastase-1 (FE1), chymotrypsin (FCht) and lipase
(FLP) output on omnivore (OV) and on modified (MD) diet
1st – 3rd
1st – 3rd
Enzyme secretion and diet155
the measurement of FCht activity served as a control
Exocrine pancreatic secretion could be assessed in different
ways. In short-term dietary modification the steady collection
of pancreatic juice could be applied (Boivin et al. 1990). How-
ever, it limits the period of observation. The effects of long-
term dietary changes could be assessed by the repeated per-
formance of direct pancreatic function tests (Zoppi et al.
1972). The maximal hormonal stimulation may not reflect
the real interdigestive and postprandial changes in pancreatic
secretion due to dietary stimulation. The disadvantage of
both methods is related to their being invasive. In the present
study, we assessed faecal output of pancreatic enzymes. Paral-
lel assessment of dietary intake and pancreatic secretion as
well as physiological way of pancreatic stimulation (diet) is
the advantage of such an attitude. Considering the limitation
of indirect pancreatic function tests we assessed daily faecal
output for 3d instead of concentration/activity in a single
stool sample. Since FE1 concentrations in healthy subjects
correlate significantly with the parameters of direct test
(Stein et al. 1996), the observed decrease of elastase-1
secretion seems to be highly reliable.
In the present study, we assessed the changes of exocrine
pancreatic secretion in a group of healthy omnivores who
modified the diet by abstaining from meat for 1 month. In
contrary to the previously assessed cross-sectional model com-
prising vegetarian and omnivore subjects (Walkowiak et al.
2006), the use of a prospective model revealed the selective
adaptation of pancreatic secretion. The dietary changes
resulted in a statistically significant decrease of pancreatic
secretion as measured by FE1 output. On the other hand,
Fcht and FLP excretions remained unchanged. Since the veg-
etarian diet is becoming increasingly popular this information
is of potential significance.
The ability of the pancreas to adapt to changes in dietary
intake was initially noted by Pavlov. Subsequent animal studies
clearly demonstrated that proteolytic, amylolytic and lipolytic
synthesis changes proportionately in response to the amount
of their respective dietary substrates: proteins, carbohydrates
and fat (Pitchumoni & Scheele, 1993). The data available for
human subjects are sparse. Zoppi et al. (1972) reported that
in premature infants a starch-enriched diet stimulated amylase
secretion, whereas a high-protein diet led to the increase of
trypsin and lipase levels. The increase of fat intake did not
result in any changes. In another study of premature infants
(Lebenthal et al. 1981), a significant increase of secretin- and
cholecystokinin-stimulated trypsin and lipase output in a sub-
group fed soya-based formula containing increased protein
was reported. In adult volunteers, low-fat and high-carbo-
hydrate diets resulted in a higher output of trypsin and chymo-
trypsin as measured by a secretin–cholecystokinin test (Emde
et al. 1985). In contrast to animal models, no adaptation of
amylase and lipase secretion was found. Boivin et al. (1990)
concluded in their study that diets containing a high proportion
of calories as carbohydrate are associated with lower interdi-
gestive and postprandial pancreatic secretion than diets with a
high fat content. Keefe (2006) reported that changing the for-
mula of the diet from polymeric to elemental in duodenally
fed subjects resulted in a 50% decrease in pancreatic secretion.
This can be explained both by the elemental nature of the diet
and by the fact that the elemental formula has a low fat content
and fat is one of the major stimulatory effects on cholecysto-
kinin release (Owyang et al. 1986). This agrees with findings
reported by Keller et al. (1997).
The changes in the intake of major dietary nutrients
observed in the present study are minor in comparison to
those in the studies described earlier. However, the qualitative
changes in fat (MUFA and PUFA) and protein profile (animal
and plant sources) were observed. According to the suggested
feedback mechanism in the control of pancreatic secretion, the
changes in the intake of protein could modify pancreatic pro-
tease output (Owyang et al. 1986). Animal and plant proteins
have different structure (Gawecki, 1997) and may potentially
cause different pancreatic secretion. However, there are no
data available concerning this subject in vegetarians. There
is also evidence that the Mediterranean diet with higher
MUFA consumption decreases pancreatic secretion (Alarcon
de la Lastra et al. 2001). The intake of MUFA was statistically
lower during the modified diet than during the omnivore
period of the study, which could hypothetically favour pan-
creatic secretion in vegetarians. On the other hand, PUFA con-
sumption was significantly lower during the 1-month period of
modified diet. The major dietary PUFA (linoleic, linolenic
and arachidonic acids) were reported to stimulate in vitro pan-
creatic secretion (Egberts et al. 2000). Therefore, the de-
crease of pancreatic secretion could be expected.
Table 2. Changes of energy and nutrient intake resulting from the change of diet (omnivore v. modified diet)
Omnivore dietModified dietRelative changes*
Nutrient MedianMean1st – 3rd quartileMedianMean1st – 3rd quartileMean
Animal protein (g)
Plant protein (g)
*Value expressed as a percentage of original value (%).
J. Walkowiak et al.156
Other factors possibly influencing pancreatic secretion in
vegetarians are higher consumption of soya-bean trypsin
inhibitors (Folsch & Creutzfeldt, 1985; Holm et al. 1992)
and dietary fibre (Isaksson et al. 1982; Dutta & Hlasko,
1985) and lower intake of Se (Jackson et al. 2003). However,
soya is commonly added to products commercially available
for omnivores. In addition, a soya-containing diet (due to
the different analytical methods) could result in a decrease
of FCht activity and would possibly result in an increased
FE1 concentration (Walkowiak & Herzig, 2004). Furthermore,
dietary fibre has been shown to affect pancreatic enzyme
activity in vivo and in vitro (Isaksson et al. 1982; Dutta &
Hlasko, 1985). Therefore, enzyme activity could be decreased
(e.g. for chymotrypsin). However, the immunoenzymatic
method determines FE1 concentrations and not activity.
Finally, Se intake in vegetarians was reported to be lower
than in omnivores (Larsson & Johansson, 2002). Possible
involvement of selenoproteins in the human pancreatic
secretory process has been suggested (Weizman, 2004) and
cannot be excluded, but has not been reported. However, the
functional consequence of decreased Se intake is unclear
(Jackson et al. 2003).
Since no significant correlation between relative and non-
relative changes of energy and nutrient consumption and pan-
creatic secretion was found, we could assume that the
observed quantitative and qualitative changes played a minor
role. The major hypothetical dietetic influence was in fact
related to the exclusion of meat from the diet. The lack of
the substrate (meat) for the enzyme (elastase-1) might be
responsible for the observed selective changes in pancreatic
enzyme secretion. The consumption of MUFA and PUFA
decreased significantly, being the ‘adverse effect’ of the diet.
The increased consumption of dairy products was the under-
lying factor. This bystander effect underlines the significance
of a thorough dietary consideration in vegetarians. However,
subjects included in the study were not regular vegetarians.
They volunteered for a 1-month period. Therefore, their diet
could not represent a genuine lactoovovegetarian diet.
It could be also the underlying cause of the lack of changes
in stool weight. Therefore, we can only comment on the influ-
ence of the exclusion of meat from the diet rather than on a
genuine lactoovovegetarian diet.
In conclusion, the exclusion of meat from the diet for a
1-month period resulted in significant changes in pancreatic
secretion with a selective decrease of elastase-1 output. How-
ever, the underlying factor remains unclear.
This investigation was supported in part by the Polish Scien-
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