Relationship between Food Intake and Finger Plethysmograms
Yoko Hirohashi, Masaki Chiba, Sang-jae Lee and Atsuko Umezawa
Faculty of Health and Welfare, Nayoro City University, W4-N8-1, Nayoro, Japan
Keywords: Food Intake, Finger Plethysmograms, Non Liner Analysis, LLE, Autonomic Nerve Balance.
Abstract: The purpose of this manner of research was to investigate the influence of food intake on the human body,
by means of data showing the chaotic fluctuations of fingertip pulse wave, through the use of nonlinear
analysis. For the measurement of the fingertip pulse wave, 5 types of meals were utilized, using both meals
where a single person ate alone with no conversation, and meals where several persons ate and conversed,
using water, hot soup, and cold soup, measurements were taken at various times (just before food intake,
just after food intake, and 30 minutes after food intake). At result, with meal intake, there was a temporary
and significant drop in LLE levels, followed by a rise in LLE when several persons ate and conversed. Most
of the participants saw little change in levels after intake of cold soup, or water. With intake of hot soup, it
was observed that a little climb in LLE levels 30 minutes after eating. Many people increased levels from
heat stimulation of the sympathetic nerve, then afterward a decrease, and there is speculation that there is a
kind of “relaxation effect”. It seems evident that partaking of warm food while in the company is a good
practice.
1 INTRODUCTION
In regard to meals, one’s diet has a physical and
emotional effect on maintenance of life activities,
maintenance and quality of health, recovery from
and prevention of disease, enjoyment of life, a sense
of contentment, seasons of life, etc. Also, in societal
relationships, communication and enjoyment of
one’s family, cultural traditions, cultural aspects
regarding ceremonial occasions, etc., diet has a large
role and meaning, and is an essential part of daily
human life.
In recent years, in dual-income families,
generally speaking, in relationship to daily lifestyle
in society, eating alone, always eating the same food,
unbalanced diet, dependence on “fast food”, etc., has
become a real problem. Because of this, in
kindergartens, elementary schools, and junior high
schools, there has been an increased realization of
the importance of “nutrition education”. In a survey
(Shinohara 2012), where there is a great deal of
instruction regarding proper diet, the effects of
“concern for good eating”, “manners”, “rhythm of
daily life”, “proper body weight”, “proper bowel
movement”, etc., can be clearly seen. Where
children are given good instruction in nutritional
education, the importance of good diet has become
very evident. Outside of activities to promote
nutritional education, there has been an expansion of
research in the following areas: studies involving the
effect of food aroma (Kunieda 2011), research in
improvement of dietary habits (Fujita 2012), studies
regarding eating/swallowing disorders in nursing
care facilities (Okada 2009).In addition, when
measuring levels of Chromogranin A found in saliva,
research showing the correlation between diet and
relief from stress, as well as levels of Cortisol found
in the bloodstream and levels of active NK cells
reveal the level of enjoyment of meals, research into
the influence of eating and exercise on the value of
oxidation stress markers, and information regarding
the value of diet on the living body can be observed.
However, regarding the relationship of diet and
brain activity, various research has been conducted
where brain waves are measured in connection with
food aroma (Sumiya 2007, Ishiguchi 2008), but
there are only a few articles that deal with
prevention of dementia in elderly persons by
controlling diet, and research using information
regarding how diet itself affects brain activity in
living persons is lacking. By analyzing the
fluctuation of the fingertip pulse wave, data
regarding the effect of the Largest Lyapunov
Exponent (LLE) index upon brain activity, as well as
253
Hirohashi Y., Chiba M., Lee S. and Umezawa A.
Relationship between Food Intake and Finger Plethysmograms.
DOI: 10.5220/0004776202530260
In Proceedings of the Third International Symposium on Business Modeling and Software Design (BMSD 2013), pages 253-260
ISBN: 978-989-8565-56-3
Copyright
c
 2013 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

information related to balance of the autonomic
nerves can be obtained. By obtaining information on
how eating cause fluctuation of the fingertip pulse
wave, more understanding can be gained as to the
influence of diet upon the human body. Knowledge
regarding the meaning of human lifestyle and diet,
obtained by data collected from these kinds of
measurements is thought to be both objective and
meaningful. Also, with Oyama and others, based on
the outcome of advances in research by observing
fluctuation of the fingertip pulse wave, information
regarding brain activity has been newly obtained,
and comparisons of fingertip pulse wave and its
correlation to food intake have been observed.
The purpose of this manner of research is to
investigate the influence of food intake on the
human body, by means of data showing the chaotic
fluctuations of fingertip pulse wave, reflecting
variations of brain activity, through the use of
nonlinear analysis technique.
2 METHOD OF STUDY
2.1 About a Finger Pulse Wave and
Calculation of Lyapunov Exponent
By means of nonlinear analysis of data from
fluctuations in fingertip pulse wave, it is possible to
obtain a numerical value of “mental revitalization”,
using the Largest Lyapunov Exponent index value.
Using advanced research methods, effectiveness of
various activities directed at mental health can be
verified. Also, using data gathered from fluctuations
of fingertip pulse wave, it is possible to determine
autonomic nerve balance (whether the sympathetic
nerve or parasympathetic nerve is dominant).
Figure 1 shows the flow diagram showing the
procedure from the measurement of pulse waves to
calculation of the Lyapunov exponent (Oyama
2006). To construct the attractor, we set a delay time
and the number of embedding dimensions according
to Tarkens theory. We used four embedding
dimensions and a delay time of 50 msec. The figure
on the right illustrates the method of embedding in
three-dimensional phase space. Although effective
information can be obtained from the shape of the
four-dimensional attractor, we calculated the
Lyapunov exponent, which is an index of trajectory
instability and has a chaotic characteristic. (Figure 1)
By measuring the fingertip pulse waves for one
minute, 43 Lyapunov exponents are obtained. We
compared each condition using an average of these
values (Oyama 2007).
Figure 1: Flow diagram showing the procedure from the
measurement of pulse waves to calculation of the
Lyapunov exponent.
2.2 Method of Measurement
2.2.1 Study Subject
For this research, 20 students currently enrolled
between the 2nd and 4th year of studies at “N”
University were used. All of the participants were
female, from 20 to 22 years of age. All were in
generally good health, with no known mental or
physical abnormalities. Before sampling fingertip
pulse wave of the participants, vital signs (body
temperature, heart rate, blood pressure) were
measured each time, and no one showed any
abnormal condition. The number of times the
experiment was conducted varied according to food
intake, from 1 to 5 times. In order to make
comparisons regarding intake of water, hot soup, and
cold soup, the same individuals were utilized.
2.2.2 Study Location
“N” University, located in “H”
2.2.3 Study Period
January, 2013
2.2.4 Measurement Detail
With each of the participants, personal data was
collected and prior explanation of the experiment
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was given, and care was given to insure adequate
ethical treatment of those involved. In addition, a
consent form was obtained from each participant,
documenting their willing cooperation with the
research.
On the day of the experiment, each participant’s
vital signs (body temperature, heart rate, blood
pressure) were measured, and verification was made
that there were no signs of unusual physical
abnormality, prior to commencement of the
experiment.
For the measurement of the fingertip pulse wave,
5 types of meals were utilized, using both meals
where a single person ate alone with no conversation,
and meals where several persons ate and conversed,
using water, hot soup, and cold soup, measurements
were taken before and after eating. At various times
(just before food intake, just after food intake, and
30 minutes after food intake), 3 different readings
were taken. For obtaining the measurements, a
chaotic Lyspect device was utilized. A cuff was used
with the device, and placed on the tip of the
participant’s right index finger, and each time a
measurement was taken for 3 minutes. The subjects
were asked to sit in an armchair, and rest their arm
quietly on a table for the duration of the
measurement. During measurement, the subjects
were asked to not speak and maintain a quiet,
unmoving position. A plan was followed where in a
single experiment 5 people were observed and their
readings were taken. In accordance with the
measuring devices, the beginning of each
experiment was carried every 5 minutes.
For the environment used in taking the
measurements, the subjects were asked to not
communicate with one another, and a large, quiet
room was used. The room temperature was 22
degrees C. The participants were seated separately in
armchairs at tables, and after taking the pre-
experiment readings were allowed to eat. After
taking the reading immediately following the meal,
the subjects were asked to sit quietly and look at
picture books. In order to prevent any influence of
written words on the body, picture books with no
words made by artist Anno Mitsumasa were used
exclusively.
The room where the subjects ate while
communicating was comparatively small, but was
free of noise and the room temperature was
maintained at approx. 22 degrees C. The participants
sat around tables, and enjoyed pleasant conversation
while eating the meal.
The meal consisted of store-bought sandwiches
and onion soup (150 ml.). The sandwich size was an
amount such that the female college students were
sufficiently full after eating. The hot and cold soups
were store-bought creamed corn soup (180 ml.), and
were consumed either after heating, or after taking
directly from the refrigerator.
Analysis of the experiments was conducted using
Lyspect software on computer, but data regarding
fluctuation of fingertip pulse wave was analyzed
immediately using nonlinear analysis technique.
3 RESULTS
3.1 Meal Intake
There were 10 participants who ate their meal alone,
one person at a time. During the meal, there was no
communication interaction with others. 5 individuals
were 2 groups of 5 people, and the experiment was
conducted 2 times.
7 participants ate a meal with pleasant
communication. One group consisted of 5 members,
but due to absence of some members, so the
remaining groups worked in pairs, conducting the
experiment 2 times.
3.1.1 LLE Index Values for Those Who Ate
Alone
1) 4 participants saw elevated LLE index levels
immediately following the meal. Of this group, 3
saw levels initially drop, and then rise again. And 1
individual saw the LLE level climb gradually.
Figure 2: No.3’s LLE. Figure 3: No.9’s LLE.
2) 3 participants saw LLE index levels drop
immediately following the meal. Of this group, 2
saw levels gradually drop, and 1 person saw their
level greatly increase and then decrease.
Relationship between Food Intake and Finger Plethysmograms
255

Figure 4: No.5’s LLE. Figure 5: No.7’s LLE.
3) 3 participants saw either no change or only very
slight changes in their LLE index level.
Figure 6: No.6’s LLE. Figure 7: No.10’s LLE.
3.1.2 LLE Index Values for Those Who Ate
While Visiting with Others
1) 4 individuals saw LLE index levels increase after
the meal. Of this group, 3 people saw their levels
increase after temporarily seeing a sharp decrease.
Figure 8: No.16’s LLE. Figure 9: No.23’s LLE.
2) 1 person showed almost no change in LLE index
levels after the experiment. This person experienced
a temporary rise and fall of the level, with the final
level nearly equal to the original level.
Figure 10: No.15’s LLE.
3) 2 participants saw LLE index levels drop.
However, they saw a large drop and then a large
increase in the levels, and while there was a great
fluctuation, the final level was nearly the same as
before the experiment began.
Figure 11: No.13’s LLE. Figure 12: No.22’s LLE.
4) 5 individuals saw their LLE levels rise after
completing the meal. Only 1 person saw their level
decrease immediately after eating, and only one
person saw nearly no change to their level.
There was a marked result in that many saw very
little fluctuation of their fingertip pulse wave.
3.1.3 Autonomic Nerve Balance Levels after
Meal Intake
There were many individuals who saw rise in
sympathetic nerve activity immediately following
food intake. Among 17 participants, 13 experienced
this. By chewing food and movement of the jaws,
and by intake of warm food, it is thought that
sympathetic nerve activity was stimulated. This is
attributed to increased nervousness and bodily
activity. Athletes experience the same kind of thing
when they chew gum.
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256

Figure 13: Autonomic nerve balance following food
intake.
Among 17 participants, 11 people saw a
mountain-shaped drop in levels 30 minutes after
food intake. That is, immediately following food
intake there was a temporary dominance of
sympathetic nerve activity, and then with the start of
digestion, within 30 minutes there was a shift to
dominance of the parasympathetic nerve activity.
Figure 14: Autonomic nerve balance 30minutes after food
intake.
3.2 Intake of Hot Soup
There were 13 participants who ate hot soup. Groups
of 3-5 members were formed for the experiment.
3.2.1 LLE after Hot Soup Intake
1) 8 people showed little change (nearly flat reading
on chart)
Figure 15: No.3’s LLE. Figure 16: No.4’s LLE.
Figure 17: No’s LLE. Figure 18: No’s LLE.
2) 3 people showed a slight increase (no decrease
after eating)
Figure 19: No.2’s LLE. Figure 20: No.11’s LLE.
3) 2 people showed a marked decrease, then an
increase (of these, 1 person’s final reading was lower
than start)
3.2.2 Autonomic Nerve Balance Levels after
Hot Soup Intake
1) 8 people showed sympathetic nerve increased
activity immediately following meal (marked
increase)
Figure 21: No.6, 11 and18’s autonomic nerve balance.
2) 7 people showed a mountain-shaped increase,
then decrease of autonomic nerve balance.
3) 4 people showed sympathetic nerve decreased
activity immediately following meal
4) 1 person showed no change
Warm drinks (hot milk, etc.) will cause drowsiness
with some people.
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257

3.3 Intake of Cold Soup
13 individuals drank cold soup, and measured their
fingertip pulse wave before and after the meal.
3.3.1 LLE after Cold Soup Intake
1) Out of 13 people, 8 people showed little change in
readings before, immediately after, and 30 minutes
after food intake.
Figure 22: No.1’s LLE. Figure 23: No.3’s LLE.
Figure 24: No.4’s LLE. Figure 25: No.14’s LLE.
2) 3 people showed an increase in LLE.
3) 1 person showed a temporary rise in LLE,
followed by a decrease, and then a return to the same
level as before the meal.
4) 1 person showed a temporary rise in LLE,
followed by a decrease to a level lower than before
the meal.
As with eating meals and drinking hot soup,
there was not one case where a person saw a
temporary drop in LLE followed by a large rise.
3.3.2 Autonomic Nerve Balance Levels after
Cold Soup Intake
1) 8 persons showed a decrease in levels in the
period from before the meal until 30 minutes
afterward (when the 3rd reading was taken).
2) Among these, 6 people saw a steady decrease in
levels from immediately after eating until 30
minutes later, and 2 people saw levels temporarily
rise sharply, followed by a decrease to lower than
original levels.
3) 2 people saw increased levels after the
experiment.
4) 2 people saw little change in levels.
The body temperature may decrease.
Figure 26: The change of autonomic nerve balance after
cold soup intake.
3.4 Intake of Water
12 individuals took readings of their fingertip pulse
wave before and after drinking water.
3.4.1 LLE after Water Intake
1) From 12 people who took readings before,
immediately after, and 30 minutes after drinking
water, 5 persons showed little change in LLE levels
Figure 27: No.4, 14 and18’s LLE.
2) 4 people showed an increase in LLE levels.
Among these, 3 people saw an immediate rise, and 1
person saw a temporary drop in LLE, followed by an
increase.
3) 3 people saw an immediate drop in LLE levels.
3.4.2 Autonomic Nerve Balance Levels after
Water Intake
1) 5 people experienced an increase in comparison
of readings before water intake (1st reading), and 30
minutes after water intake (3rd reading).
2) Among these, 3 people showed a temporary
decrease in levels just after water intake, followed
by an increase. 2 people saw an immediate rise in
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levels. 1 person saw an initial rise, followed by a
decrease.
3) 5 people saw a decrease in comparison of
readings before water intake (1st reading), and 30
minutes after water intake (3rd reading).
4) Among these, 3 people saw a temporary slight
rise in levels immediately following water intake,
and then a drop to levels lower than before intake. 2
people saw a drop in levels, followed by an increase
to a back to a level lower than at the beginning.
5) 1 person saw only a slight change in their levels.
6)- All told, the split between people who saw a rise
after water intake, and those who saw a drop was
50/50.
Figure 28: Change of ANB after water intake.
Because of cold soup and corn pottage, and
because of long periods of time where the stomach
was in a cold condition, it is considered that this is
why there was a small proportion of persons whose
levels rose 30 minutes after food intake. In the case
of water, it is thought that this is due to absorption of
the water within 15 minutes of intake.
4 CONCLUSIONS
With food intake, the frequent pattern was that
immediately following a meal, there was a
temporary and significant drop in LLE levels,
followed by a rise in LLE. Most of the participants
saw little change in levels immediately after intake
of hot soup, cold soup, or water. By observing this
only, it was learned that meals have a significant
influence on the body. When well-chewed food
enters the stomach, it appears that the brain’s natural
response is to trigger a “digestion” bodily activity,
and due to a change in blood flow, it is thought that
the LLE level, which indicates temporary brain
activity, is lowered. It has been verified that LLE
shows the adaptability of the outer portion of the
mind, however, “immediately following food
intake” centers on the act of eating, so it is
understood to be a natural result that LLE adaptation
in the outer portions become less. Therefore, when a
major activity is being undertaken, before a test,
ensuring that participants do not have a full stomach
is considered the appropriate means, and is verified
by bodily information. However, in the group where
several people enjoyed a meal and afterward had
enjoyable conversation together, LLE levels in
everyone increased, and participants’ sense of
awareness was also much enjoyed. When
considering that these participants’ felt the food was
delicious and were totally satisfied, it was realized
that it is desirable to enjoy meals with close friends
or family, and even though LLE levels immediately
following eating were low, after this there was a
great shift with LLE levels increasing, and an
increase of mental activity.
Regarding results immediately following food
intake, it was observed that many individuals saw
the sympathetic nerve become dominant. However,
as mentioned above, movement of the mouth and
chewing activity is considered to cause a sharp
increase in sympathetic nerve activity. In order to
see parasympathetic nerve domination within 30
minutes of eating, activity like making the mouth
move by chewing gum is thought to be effective. For
this study, because the setting involved food intake,
the phenomenon of decreased LLE levels
immediately following food intake was seen, but
there is a great interest to verify what effect simply
chewing of food has on LLE levels. From the
results of this survey, since it was observed that
following food intake the parasympathetic nerve
became dominant, it is obvious that, as expected,
“rest from food” becomes necessary. Hypothetically,
predicting that food intake has a healthy effect on
the mind, it was possible to predict that after food
intake LLE levels would rise. However, it was
observed that initially LLE levels dropped before
rising, and following the meal parasympathetic
nerve activity and digestion activity commenced,
and it was observed that resumption of work
activities while the body experienced rest from food
was appropriate. It is obvious that the activity of
eating food is a significant source of work in
humans, and an important activity in daily life
However, for participants of the group who took
their meals alone, there were many cases where LLE
levels either immediately lowered, or had very little
fluctuation. This group included individuals who
always were relaxed while eating and then became
drowsy, and were aware of the effect of eating. In
this way, it could be observed that there are varying
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levels of awareness as to the effects of eating on the
body, and that for about 30 minutes after food
intake, many people experience mental fatigue.
With intake of only small amounts of soup, LLE
levels fluctuated very little. However, with intake of
hot soup, it was observed that a significant number
of participants who initially experienced little LLE
fluctuation did see a climb in LLE levels 30 minutes
after eating. Many people increased levels from heat
stimulation of the sympathetic nerve, then afterward
a decrease, and there is speculation that there is a
kind of “relaxation effect” that they experienced. It
seems that if a person wishes to be calm and relaxed,
drinking something warm is effective. Similar to the
fast absorption of plain warm water, for this
experiment we used pottage soup, warm milk, kudzu
starch gruel, etc., and it seems that hot beverages for
comparatively long times in the stomach are
beneficial.
Regarding intake of cold food, since it appears
that there are many people whose LLE levels and
autonomic nerve balance see little variation, it is
thought that rather than cold food, hot food has a
better effect on the body.
For participants who drank water and after 30
minutes saw a rise in sympathetic nerve dominance,
it is believed that the result of seeing low levels after
taking cold pottage soup is due to the fact that
absorption of the liquids is rapid.
From these results, it seems evident that
partaking of warm food while in the company of
friends or family is a good practice. In Japanese
society, the recent and rapid increase of young
people and elderly who live alone and eat cold food
appears to be a hindrance to overall health of the
mind and body, and adversely affects quality of life.
It seems obvious that eating of meals and good
nutrition are very necessary for QOL (Quality of
Life), and that this has been verified by the readings
measured in the human body during this experiment.
In the future, it seems apparent that more
research should be done to investigate the effects of
what occurs when one eats food that is liked, what is
the optimum environment and time for meals, as
well as other variables.
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