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Two studies were conducted to investigate the effects of red pepper (capsaicin) on feeding behaviour and energy intake. In the first study, the effects of dietary red pepper added to high-fat (HF) and high-carbohydrate (HC) meals on subsequent energy and macronutrient intakes were examined in thirteen Japanese female subjects. After the ingestion of a standardized dinner on the previous evening, the subjects ate an experimental breakfast (1883 kJ) of one of the following four types: (1) HF; (2) HF and red pepper (10 g); (3) HC; (4) HC and red pepper. Ad libitum energy and macronutrient intakes were measured at lunch-time. The HC breakfast significantly reduced the desire to eat and hunger after breakfast. The addition of red pepper to the HC breakfast also significantly decreased the desire to eat and hunger before lunch. Differences in diet composition at breakfast time did not affect energy and macronutrient intakes at lunch-time. However, the addition of red pepper to the breakfast significantly decreased protein and fat intakes at lunch-time. In Study 2, the effects of a red-pepper appetizer on subsequent energy and macronutrient intakes were examined in ten Caucasian male subjects. After ingesting a standardized breakfast, the subjects took an experimental appetizer (644 kJ) at lunch-time of one of the following two types: (1) mixed diet and appetizer; (2) mixed diet and red-pepper (6 g) appetizer. The addition of red pepper to the appetizer significantly reduced the cumulative ad libitum energy and carbohydrate intakes during the rest of the lunch and in the snack served several hours later. Moreover, the power spectral analysis of heart rate revealed that this effect of red pepper was associated with an increase in the ratio sympathetic: parasympathetic nervous system activity. These results indicate that the ingestion of red pepper decreases appetite and subsequent protein and fat intakes in Japanese females and energy intake in Caucasian males. Moreover, this effect might be related to an increase in sympathetic nervous system activity in Caucasian males.
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Effects of red pepper on appetite and energy intake
Mayumi Yoshioka
1
, Sylvie St-Pierre
1
, Vicky Drapeau
1
, Isabelle Dionne
1
, Eric Doucet
1
,
Masashige Suzuki
2
and Angelo Tremblay
1
*
1
Physical Activity Sciences Laboratory, PEPS, Laval University, Ste-Foy, Que
´
bec, Canada G1K 7P4
2
Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Ibaraki 305, Japan
(Received 2 July 1998 Revised 4 January 1998 Accepted 8 March 1999)
Two studies were conducted to investigate the effects of red pepper (capsaicin) on feeding
behaviour and energy intake. In the first study, the effects of dietary red pepper added to high-fat
(HF) and high-carbohydrate (HC) meals on subsequent energy and macronutrient intakes were
examined in thirteen Japanese female subjects. After the ingestion of a standardized dinner on the
previous evening, the subjects ate an experimental breakfast (1883kJ) of one of the following
four types: (1) HF; (2) HF and red pepper (10 g); (3) HC; (4) HC and red pepper. Ad libitum
energy and macronutrient intakes were measured at lunch-time. The HC breakfast significantly
reduced the desire to eat and hunger after breakfast. The addition of red pepper to the HC
breakfast also significantly decreased the desire to eat and hunger before lunch. Differences in
diet composition at breakfast time did not affect energy and macronutrient intakes at lunch-time.
However, the addition of red pepper to the breakfast significantly decreased protein and fat
intakes at lunch-time. In Study 2, the effects of a red-pepper appetizer on subsequent energy and
macronutrient intakes were examined in ten Caucasian male subjects. After ingesting a
standardized breakfast, the subjects took an experimental appetizer (644kJ) at lunch-time of
one of the following two types: (1) mixed diet and appetizer; (2) mixed diet and red-pepper (6g)
appetizer. The addition of red pepper to the appetizer significantly reduced the cumulative ad
libitum energy and carbohydrate intakes during the rest of the lunch and in the snack served
several hours later. Moreover, the power spectral analysis of heart rate revealed that this effect of
red pepper was associated with an increase in the ratio sympathetic :parasympathetic nervous
system activity. These results indicate that the ingestion of red pepper decreases appetite and
subsequent protein and fat intakes in Japanese females and energy intake in Caucasian males.
Moreover, this effect might be related to an increase in sympathetic nervous system activity in
Caucasian males.
Red pepper: Appetite: Energy intake: Sympathetic nervous system activity
Dietary fat intake has markedly increased with indus-
trialization in many countries (Leaf & Weber, 1987).
Experimental (Lissner et al. 1987; Tremblay et al. 1989,
1991) and cross-sectional (Lissner et al. 1987; Tremblay
et al. 1989, 1991) studies have demonstrated that a higher
fat content in the diet is associated with an increase in daily
energy intake. This is not without consequence since high
fat intake seems to be associated with increased body
fatness (Dreon et al. 1988; Romieu et al. 1988). Warwick
& Schiffman (1992) reviewed the literature related to the
role of dietary fat in energy intake and body-weight gain in
human subjects and laboratory animals. They concluded
that both energy intake and expenditure are modified to
favour positive energy balance when a high-fat (HF) diet is
consumed and that the high energy density of HF diets plays
a primary role in weight gain. This effect of HF intake on
energy and lipid balance might be explained by the fact
that experimental evidence supports the idea that high-
carbohydrate (HC) diets are more satiating than HF diets
(Thomas et al. 1992; Blundell et al. 1993; Lawton et al.
1993; Stubbs et al. 1995) and that the reduction of fat intake
when fat is replaced by a fat substitute does not result in
increased hunger or full compensation of decreased energy
intake (Westerterp-Plantenga et al. 1997). Therefore, it
could be concluded that a HF diet is characterized by a
lower potency to prevent overfeeding. From a public health
standpoint, the overfeeding resulting from a HF dietary
regimen probably represents one of the factors responsible
for the high prevalence of obesity observed in industrialized
countries.
Capsaicin, which is the major pungent principle in hot red
pepper, has long been used as an ingredient of spices all over
British Journal of Nutrition (1999), 82, 115123 115
Abbreviations: HC, high carbohydrate; HF, high fat; SNS, sympathetic nervous system.
*Corresponding author: Dr Angelo Tremblay, fax +1 418 656 2441, email angelo.tremblay@kin.msp.ulaval.ca
the world. Kawada and colleagues (Kawada et al. 1986)
have reported that the addition of capsaicin to a HF diet
lowers perineal adipose tissue weight in rats in a dose-
dependent manner. We have also reported that the addition
of capsaicin to a HC diet results in a reduction of the
epididymal adipose tissue weight at the same energy
intake (Matsuo et al. 1996). These results indicate that
addition of capsaicin to foods could reduce adiposity, a
phenomenon which can be explained partly by the
enhancing effects of capsaicin on energy and lipid
metabolism via catecholamine secretion from the adrenal
medulla in rats (Watanabe et al. 1987a,b; Kawada et al.
1988). Since an increase in sympathetic nervous system
(SNS) activity affects food intake behaviour (Russek et al.
1987; Bray, 1991; Raben et al. 1996), we hypothesized that
the addition of red pepper (capsaicin) to the diet can
decrease food intake and that this is associated with an
increase in SNS activity. Specifically, in a first study we
investigated whether the addition of red pepper to breakfasts
of differing macronutrient composition could influence
subsequent food intake and subjective feelings of hunger
and satiety. Moreover, in order to document further the
effects of red pepper on human eating behaviour, we
performed a second study to investigate whether the addi-
tion of red pepper to an appetizer could influence subse-
quent food intake and whether this effect is related to
concomitant changes in SNS activity.
Methods
Studies 1 and 2 were designed to test the impact of red
pepper in real-life settings. In Study 1, we wanted to
measure the impact of red pepper (capsaicin) added to
meals (in this case breakfast meals) of differing macro-
nutrient composition (HF v. HC) on subsequent subjective
feelings of hunger and satiety as well as on subsequent
ad libitum energy and macronutrient intakes at lunch-time
(3h following this test meal). Study 2 was designed to
measure the impact of a preload (appetizer) with or without
red pepper on ad libitum energy and macronutrient intakes
immediately after consumption of this preload. Since many
authors have tested similar hypotheses with a test meal
given at breakfast time (see, for example, Blundell et al.
1993), we decided to adopt the same procedure. In order to
be concordant with Study 1, we then had to measure ad
libitum food intake after the appetizer at lunch-time. In a
sense, we did not aim to reproduce the results of Study 1
with those of Study 2; rather we wanted to document further
the impact of red pepper on human ad libitum food
consumption. This is the main reason for the apparent
differences of design between Studies 1 and 2.
Study 1
Subjects. Thirteen healthy Japanese females (age 258
(
SD 28) years, weight 542(SD 64) kg, height 157
(
SD 004)m, body fat 253(SD 47)%) volunteered to
participate in this study. The participants were asked to
maintain their regular dietary habits and to abstain from
intake of alcohol and caffeine on the day before the
investigation. Strenuous physical activity was not allowed
for 2d before each experimental session to prevent the
stimulation of energy metabolism (Bielinski et al. 1985;
Bahr et al. 1987; Tremblay et al. 1988). All subjects were
tested during the follicular phase of the menstrual cycle.
The written consent of each subject was obtained before
admission to the study; experimental procedures conformed
to the Declaration of Helsinki.
Experimental protocol and measurements. The experi-
mental protocol of this study was designed to investigate the
effects of red pepper added to HF and HC meals on
subsequent energy and macronutrient intakes. A detailed
description of the composition of the red pepper used
(Saemaul Kongjang 1) is given in Table 1. The subjects
consumed a standardized dinner (15, 25 and 60% energy
from protein, fat and carbohydrate respectively) on the day
before each session. On the next morning, they participated
randomly in one of four test sessions which consisted of
the measurements of energy and macronutrient intakes 3 h
after the experimental meals, each of which provided
1883kJ. These meals differed between sessions according
to the following specifications: HF meal (% energy: protein
15, fat 45, carbohydrate 40), HF and red-pepper (10g) meal,
HC meal (% energy: protein 15, fat 25, carbohydrate 60),
and HC and red-pepper meal. The subjects rested on a
chair in a semi-reclining position for 3 h to perform calori-
metric measurements after the meals. At lunch-time, the
subjects were instructed to eat ad libitum in the laboratory
until satiated. To facilitate the measurement of food intake,
food was prepared and pre-portioned. After each meal,
quantities of foods that were not entirely consumed were
reweighed to determine net intake of each food. The
Canadian Nutrient File 1991 software was used to calculate
energy, protein, lipid and carbohydrate intakes from these
measurements.
Prospective food consumption, desire to eat, hunger,
fullness and satiety were measured immediately before
and after the breakfast and lunch by using a 150mm
visual analogue scale, as further described in Table 2,
which was adapted from the method previously described
by Hill & Blundell (1986). All results obtained with the
116 M. Yoshioka et al.
Table 1. The composition of dried hot red pepper (Data from Ku &
Choi, 1990)
Component Content
Crude component (g/kg)
Moisture 194
Protein 109
Fat 152
Carbohydrate 462
Ash 78
Capsaicin 3
Minerals (g/kg)
Calcium 1230
Phosphorus 1400
Iron 1000
Vitamins (mg/kg)
A211
Thiamin 3
Riboflavin 2
C 2200
Metabolic energy (kJ/g) 101
visual analogue scale were converted to scores ranging from
0 to 100 for statistical analysis.
Because elemental conditions and the physical state of
foods affect spontaneous energy intake in human studies
(Kissileff, 1985; Himaya & Louis-Sylvestre, 1998), pre-
cautions were taken to maximize the reliability of
experimental conditions: subjects were given standardized
instructions, the confounding effect of external factors such
as light and noise was minimal, the time interval between
meals was comparable in each session, and foods used were
normally eaten by subjects.
Statistical analysis. A three-way ANOVA for repeated
measures was used to determine effects of diet compo-
sition, red pepper and time as well as their interactions
on prospective food consumption, desire to eat, hunger,
fullness and satiety. We also used a two-way ANOVA to
determine the effect of diet composition × red pepper as
well as the diet composition × red pepper interaction on
energy and macronutrient intakes. When the ANOVA
revealed a significant effect, a contrast analysis adjusting
for multiple comparisons was applied to identify which
conditions differed from each other. Differences were con-
sidered to be statistically significant at P, 005. Statistical
analyses were performed with SuperAnova Software,
version 1.11, q Abacus Concepts, Inc. 1991, Cary, NC,
USA. All results are expressed as means with their standard
errors.
Study 2
Subjects. Ten healthy Caucasian males (age 329(
SD 78)
years, weight 725(
SD 101)kg, height 175 (SD 006)m)
volunteered to participate in this study. The instructions to
participants were the same as those in Study 1. The written
consent of each subject was obtained before admission to
the study; experimental procedures conformed to the
Declaration of Helsinki.
Experimental protocol and measurements. The experi-
mental protocol of this study was designed to investigate
the effects of an appetizer containing red pepper on
subsequent energy and macronutrient intakes. The subjects
consumed a standardized breakfast (% energy: protein 18,
fat 39, carbohydrate 43) and they participated randomly in
the two test sessions which consisted of measurement
of ad libitum energy and macronutrient intakes after the
experimental appetizers at lunch-time. In each session, the
energy content of the appetizer was 644kJ (% energy:
protein 15, fat 29, carbohydrate 56) and it differed only in
red pepper content (0 v. 6g red pepper). After consuming
the appetizer, the subjects were instructed to eat ad libitum
until satiety was reached. A snack was also offered in the
middle of the afternoon (3h after lunch) and the subjects
were again instructed to eat ad libitum. The procedures to
measure food intake were identical to those used in Study 1.
Heart-rate power spectral analysis was performed
throughout the experiment using an electrocardiograph
(Q4000 Quinton, Seattle, WA, USA). The electrocardio-
graphic signals were digitized, stored on hard disk and
sampled at a rate of 500 Hz, with twelve precision bits.
The QRS complex (lead II) was automatically recognized
by a classic derivative/threshold algorithm. Power spectra
were calculated from a consecutive series of 512 R-R
intervals. As previously reported (Pomeranz et al. 1985;
Arai et al. 1989), the ratio low-frequency (004015 Hz
Eq):high-frequency (015050Hz Eq) components of
spectra was used as an indicator of the ratio sympathetic :
parasympathetic nervous system activity. It has been
reported that the intra-individual CV of heart-rate spectral
analysis measured four times over 27 d was 167% (Hirsch
et al. 1991). It has also been found that this method provides
realistic information about changes in SNS activity in
the context of experimental overfeeding and underfeeding
(Aronne et al. 1995).
Statistical analysis. A two-way ANOVA for repeated
measures was used to determine effects of red pepper and
time as well as their interactions on dependent variables,
whereas a three-way ANOVA was used to determine the
effects of time, red pepper, diet composition, and their
interaction on prospective food consumption, desire to eat,
hunger, fullness and satiety. When the ANOVA revealed a
significant effect, a contrast analysis adjusting for multiple
comparisons was applied to identify which conditions
differed from each other. Pearson’s correlation coefficients
were calculated to quantify the associations between
changes in energy intake and those derived from the
power spectral analysis of heart rate. Differences were
considered to be statistically significant at P, 005.
Statistical analyses were performed with SuperAnova
Software, version 1.11, q Abacus Concepts, Inc. 1991.
117Red pepper and energy intake
Table 2. Description of the visual analogue scale used for measurement of prospective food
consumption, desire to eat, hunger, satiety and fullness
Variable Question
Prospective food 1) How much food do you think you could eat?
consumption No food at all |——————————————————| A large amount
Desire to eat 2) How strong is your desire to eat?
Very weak |——————————————————| Very strong
Hunger 3) How hungry do you feel?
Not at all |——————————————————| As hungry as I
hungry have ever felt
Satiety 4) What is your level of satiety?
Not satiated at all |——————————————————| Very high
Fullness 5) How full do you feel?
Not at all full |——————————————————| Very full
All results are expressed as means with their standard
errors.
Results
Study 1
Effects of red pepper added to HF and HC breakfasts on
energy and macronutrient intakes are presented in Table 3.
The macronutrient composition of breakfast did not affect
the weight of ingested food, or energy and macronutrient
intakes at lunch-time. However, the addition of red pepper
to breakfast significantly decreased protein intake (by 20%
and 6% for HF and HC conditions respectively, P , 005)
and fat intake (by 17% and 11% for HF and HC conditions
respectively, P, 005) at lunch-time. Red pepper also
tended to decrease energy intake (11% and 4% for HF
and HC conditions respectively) but this effect did not reach
statistical significance.
Variations in prospective food consumption, desire to eat,
hunger, fullness and satiety as measured by visual analogue
scales are shown in Fig. 1. Prospective food consumption
was significantly higher in the HF meal condition imme-
diately after the breakfast and before the lunch. The addition
of red pepper to experimental meals significantly decreased
the prospective food consumption immediately before the
lunch whereas the opposite effect was seen after the lunch.
Desire to eat was significantly higher in the HF meal
conditions immediately after the breakfast, but red pepper
corrected this effect by significantly decreasing the desire to
eat immediately after the breakfast and before the lunch.
Hunger was significantly higher in the HF meal conditions
immediately after the breakfast and the addition of red
pepper to the experimental meals significantly decreased
this variable immediately after the breakfast and before the
lunch. Fullness and satiety were not significantly modified
by the experimental meals.
Study 2
The effects of the red-pepper appetizer on energy and
macronutrient intakes are shown in Table 4; these values
do not include the energy and macronutrient content of the
appetizer. The addition of red pepper to the experimental
appetizer significantly decreased cumulative (lunch+
mid-afternoon snack) carbohydrate intake (18%, P, 005)
and energy intake (11 %, P , 005) at lunch and snack.
Fig. 2 presents changes in the sympathetic :parasym-
pathetic nervous system activity ratio as reflected by changes
in the low :high frequency ratio of the power spectra as
measured by power spectral analysis of heart rate. The addi-
tion of red pepper to the experimental appetizer significantly
increased the sympathetic :parasympathetic nervous system
activity ratio during and immediately after the appetizer
ingestion. However, there was no further effect of the red
pepper appetizer during or after the ad libitum lunch.
The correlation between changes in the sympathetic :
parasympathetic nervous system activity ratio from baseline
and energy intake is shown in Fig 3. Changes in the sym-
pathetic :parasympathetic nervous system activity ratio
tended to be negatively correlated with energy intake, but
this effect failed to reach standard statistical significance
(P=009).
In the two studies, no subject reported nausea or any other
unpleasant effects related to red pepper ingestion. Although
this issue was not investigated with specific questions, the
absence of unpleasant sensations related to red-pepper
ingestion suggests that its effects were not explained by a
transitory discomfort under the red-pepper condition.
Discussion
The results of these studies indicate that the ingestion of red
pepper decreases subsequent protein and fat intakes as well
as appetite in Japanese females. In Caucasian males, red-
pepper ingestion reduces spontaneous energy intake, an
effect which might be related to an increase in SNS activity.
Addition of capsaicin to the diet is known to affect energy
metabolism by activating the SNS in animals (Watanabe
et al. 1987a,b; Kawada et al. 1988), and an increase in SNS
activity is known to favour a decrease in food intake
(Russek et al. 1987; Bray, 1991; Raben et al. 1996). In
the present study, we investigated the effects of dietary red
pepper on energy and macronutrient intakes. The impact of
diet composition on feeding behaviour and subsequent
energy intake was also examined.
Effect of diet composition on food intake behaviour
In Study 1, the desire to eat and the level of hunger
immediately after the HF breakfast were greater than
those observed after the HC breakfast. The prospective
food consumption was also greater immediately after the
118 M. Yoshioka et al.
Table 3. Study 1. Energy and macronutrient intakes at lunch-time after the ingestion of a high-fat (HF), HF red-pepper (HF+RP),
high-carbohydrate (HC) or HC red-pepper (HC+RP) breakfast*
(Mean values and standard deviations for thirteen subjects)
Breakfast HF HF + RP HC HC + RP
Significant
Mean
SD Mean SD Mean SD Mean SD effect†
Food intake (g) 786 66 702 76 768 67 738 80
Protein intake (g) 28637229352834026643RP
Fat intake (g) 29631247302923326134RP
Carbohydrate intake (g) 1043135 1000132 1018126 1033119
Energy intake (kJ) 3340 381 2988 352 3281 368 3155 356
*For details of meals and procedures, see pp. 116117.
Significant effect determined by two-way ANOVA,
P
, 005. There was no significant diet×RP interaction.
119Red pepper and energy intake
Fig. 1. Study 1. Values for prospective food consumption, desire to eat, hunger, fullness and satiety, measured by a visual analogue scale
(Table 2), immediately before and after high-fat and high-carbohydrate breakfasts with or without red pepper, and before and after a subsequent
lunch-time meal. The breakfasts were: (−−W−−), high fat; (X), high fat plus red pepper; (−−K−−), high carbohydrate; (O), high
carbohydrate plus red pepper. Values are means for thirteen subjects. There was a significant effect of diet composition by three-way ANOVA,
*
P
, 005, and a significant effect of red pepper by three-way ANOVA, †
P
, 005.
Table 4. Study 2. Energy and macronutrient intakes at lunch-time and snack time after the ingestion of a control or red-pepper (RP) appetizer*
(Mean values and standard deviations for ten subjects)
Control appetizer Red-pepper appetizer
Lunch Snack Lunch Snack
Significant
Mean
SD Mean SD Mean SD Mean SD effect†
Food intake (g) 979 94 373 94 943 70 290 73 T
Protein intake (g) 528727119467678325T
Fat intake (g) 65632134326236713739T
Carbohydrate intake (g) 1335105608135 112898458120T,RP
Energy intake (kJ) 5583 598 1645 343 5018 456 1419 372 T, RP
T, time.
*For details of meals and procedures, see pp. 116118.
Significant effect determined by two-way ANOVA,
P
, 005. There was no significant T×RP interaction.
HF breakfast and before the lunch than for the HC breakfast
condition. These results are in agreement with those of
previous studies which demonstrated that HF foods have a
weak potential to promote satiety acutely (Blundell et al.
1993; Lawton et al. 1993). However, the present results
show that these changes were not associated with significant
changes in ad libitum food and energy intakes at lunch-time.
The lack of a statistically significant difference in energy
intake might be due to the absence of a change in carbo-
hydrate intake but may also be attributable to a type 2 error
caused by a lack of statistical power due to the large
between-subject variation in the response to the ingestion
of red pepper.
Effect of red pepper on food intake behaviour
It is generally believed that red pepper is used for increasing
appetite under conditions of high temperature and humidity
during summer time in Japan. However, experimental
evidence suggests that capsaicin has the potential to
decrease food intake in animals, an effect that might be
mediated by SNS activity (Watanabe et al.1987a,b;
Kawada et al. 1988). The addition of red pepper to breakfast
significantly decreased protein and fat intakes at lunch-
time in Study 1, and the red-pepper appetizer decreased
carbohydrate and energy intakes in Study 2. Moreover,
these changes in macronutrient intake were accompanied
by changes in appetite such as decreased prospective food
consumption, desire to eat and hunger in Study 1. This
difference between popular belief and experimental data
may be explained in part by the amount of the spice
ingested. Indeed, high doses of capsaicin were used in the
injection studies with rats (Watanabe et al. 1987a,b;
Kawada et al. 1988) and in the studies where oral admin-
istration of capsaicin or red pepper was performed in rats or
human subjects (Kawada et al. 1986; Yoshioka et al. 1995;
Matsuo et al. 1996; Lim et al. 1997) compared with the
habitual consumption in Japan. Therefore there is a possi-
bility that a small to moderate level of red pepper in the diet
might increase food intake. Since the number of papers
which document the effects of red pepper in human subjects
is quite limited, further research would be needed to clarify
the effects of different doses of red pepper on food and/or
energy intake.
Relationship between sympathetic nervous system
activity and food intake behaviour
Bray (1993) has proposed that SNS activity affects food
intake. Moreover, Raben et al. (1996) have recently demon-
strated an association between postprandial noradrenaline
120 M. Yoshioka et al.
Fig. 2. Study 2. Values for thesympathetic:parasympathetic nervoussystem
activity ratio (expressed as the low:high frequency ratio of the power spectra
as measured by power spectral analysis of heart rate) before and after
ingestion of a control appetizer (−−A−−) and an appetizer containing red
pepper(−−B−−).Valuesaremeansfor tensubjects,withtheir standarderrors
represented by vertical bars. There was a significant effect of red pepper
determined by two-way ANOVA, *
P
, 005.
Fig. 3. Study 2. Correlation between changes in the sympathetic:
parasympathetic nervous system activity ratio (expressed as the
low:high frequency ratio of the power spectra as measured by
power spectral analysis of heart rate) and energy intake at lunch-
timeandsnackmealsinsubjectsconsumingacontrolappetizer(A)or
an appetizer containing red pepper (B). Values were obtained in ten
subjects who participated in two testing sessions. The relationship is
describedby the equation:
Y
=−1847
X
+6070 (
P
=00895,
r
0390).
release and the appetite scores. Therefore, these observa-
tions imply that increasing SNS activity should result in a
decrease in ad libitum food intake. In Study 2, the addition
of red pepper to the experimental appetizer significantly
decreased energy intake at lunch-time and significantly
increased the sympathetic: parasympathetic nervous system
activity ratio during and immediately after ingestion of
the appetizer. Moreover, D sympathetic : parasympathetic
nervous system activity ratio tended to be negatively
correlated with energy intake. If we postulate that this
change in the sympathetic:parasympathetic nervous system
activity ratio reflects an increase in SNS activity, theseresults
are in agreement with those of Russek et al. (1987) who
demonstrated that catecholamines, especially adrenaline,
have an anorectic effect that may be due to a modification
of the hepatic metabolism. We have recently reported that
there is a peak increase in catecholamine levels immediately
after red-pepper ingestion (Lim et al. 1997) and that the
increase in thermogenesis immediately after the ingestion
of red pepper is abolished by a b-adrenergic blockade
(Yoshioka et al. 1995). Thus, these changes in catechol-
amines might have also affected the feeding behaviour in
the present studies. The latter observations suggest that
spicy foods taken as an appetizer could be a successful
prescription to decrease subsequent ad libitum energy intake
and to increase thermogenesis, because spices such as red
pepper increase SNS activity.
In summary, the addition of red pepper to a meal
decreased the desire to eat as well as protein and fat intakes
at the next meal in Japanese subjects. Moreover, the addi-
tion of red pepper to an appetizer at lunch-time decreased
carbohydrate and energy intakes at lunch and snack meals in
Caucasians. These changes in energy intake tended to be
negatively correlated with the increase in the sympathetic :
parasympathetic nervous system activity ratio as measured
by power spectral analysis of heart rate. These results
suggest that the addition of red pepper to the diet decreases
energy intake, an effect which might be mediated by an
increase in SNS activity.
Acknowledgement
This study was supported by the Natural Sciences and
Engineering Research Council of Canada.
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Appendix
Study 1
122 M. Yoshioka et al.
Table 1. Compositions of the high-fat and high-carbohydrate breakfast meals
Food Weight (g) Energy (kJ) Protein (g) Fat (g) Carbohydrate (g)
High-fat breakfast
Scallops 264 1071530305
Green peppers 433519000128
Onions 410628000135
Tomatoes 423389 0.0 0120
Shrimps 201946440402
Rice (cooked) 1268 66363004358
Bacon 370 69874116603
Oil 44 1657004400
Total: g 3413169225451
kJ 18832 2820 8465 7547
(kcal) (4501) (674) (2023) (1804)
% energy 150449401
High-carbohydrate breakfast
Scallops 100406200102
Green peppers 370444000124
Onions 340523000129
Tomatoes 655598000231
Shrimps 380 1782840804
Rice (cooked) 2065 108075006582
Bacon 142 2682166401
Oil 42 1582004200
Total: g 4094169125674
kJ 18828 2827 4722 11278
(kcal) (4500) (676) (1129) (2696)
% energy 150251599
Table 2. Listof foodsserved(in largeamounts)during thelunch-time
buffet
Cola Red apples Cucumber
7-upt Bananas Lettuce
Apple juice Oranges Tomatoes
Orange juice White bread Sliced ham
Milk (35% fat) Muffins Brie cheese
Tea Melbat toasts Turkey
Oreot cookies White rice Salami
Tea biscuits Celery Fish
Fruit yoghurt Carrots Nori (Japanese food)
Ketchup Soya sauce Chazuke (Japanese food)
Mustard Butter
Study 2
123Red pepper and energy intake
Table 3. Compositions of the red-pepper and control appetizers
Food Weight (g) Protein (g) Fat (g) Carbohydrate (g)
Red-pepper appetizer
White bread 18 151 068 864
Tomatoes 10 007 001 033
Pimentoes 5 005 001 021
Cream cheese (regular) 8 085 133 032
Red pepper 3 033 046 139
Total: g 4402825109
kJ 3230469937 1824
% energy 1000146290564
Control appetizer
White bread 205171 078 984
Tomatoes 10 007 001 033
Pimentoes 5 005 001 021
Cream cheese (regular) 10 107 167 040
Total: g 4552925108
kJ 3222485929 1803
% energy 1000151289560
Table 4. Lists of foods served (in large amounts) during the
lunch-time buffet
Turkey Ketchup Fudge
Salmon White bread Milk (1% fat)
Pa
ˆ
te
´
Crackers Milk (2% fat)
Ham (Premium plust) Milk (325% fat)
Gruye
`
re cheese Lettuce Orange juice
Mozzarella cheese Tomatoes Apple juice
Cottage cheese Carrots Cola
Butter Oranges 7-upt
Mayonnaise Apples Crisps
Vinegar Tea biscuits (Rufflest rippled)
Mustard Fruit yoghurt Water
Table 5. Lists of foods served (in large amounts) during
the afternoon snack
Milk (2% fat) Chocolate cookies
Cola Oreot cookies
7-upt Crackers (Premium plust)
Quaker Dipp Barst Ritzt crackers
Crisps (Rufflest rippled) Tea biscuits
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