Psychology
2014. Vol.5, No.2, 172-176
Published Online February 2014 in SciRes (http://www.scirp.org/journal/psych) http://dx.doi.org/10.4236/psych.2014.52027
OPEN ACCESS
172
Effects of Cow Milk Intake at Breakfast on the Circadian
Typology and Mental Health of Japanese Infants Aged 1 - 6 Years
Hitomi Takeuchi1, Kai Wada1, Kiyoko Kawasaki1, Milada Krejci2,3, Teruki Noji4,
Takahiro Kawada5, Miyo Nakade6, Tetsuo Harada1*
1Laboratory of Environmental Physiology, Graduate School of Integrated Arts and Sciences,
Kochi University, Kochi, Japan
2Department of Health Education, Faculty of Education, University of South Bohemia,
České Budějovice, Czech Republic
3Faculty of Physical Education, Palestra University, Prague, Czech Republic
4Department of Physical Education, Faculty of Education, Kochi University, Kochi, Japan
5Aoyama-Gakuin University, Tokyo, Japan
6Department of Nutritional Management, Faculty of Health and Nutrition,
Tokai Gakuen University, Miyoshi, Japan
Email: rhythmsyn@hotmail.co.jp, spitz_czech@yahoo.co.jp, b12m6b11@s.kochi-u.ac.jp,
krejci@pf.jcu.cz, noji@kochi-u.ac.jp, kawadanary@hotmail.com,
nakade34@go.enjoy.ne.jp, *haratets@kochi-u.ac.jp
Received January 7th, 2014; revised Februa ry 1st, 2014; accepted February 19th, 2014
Copyright © 2014 Hitomi Takeuchi et al. This is an open access a rticle distrib uted un der the Creative Co mmons
Attribution License, which pe rmits unrestricted use, distribution, and reproduction in any medium, provided the
original work is properly cited. In accordance of the Creative Commons Attribution License all Copyrights ©
2014 are reserved for SCIRP an d the owner of the intellectual prop erty Hitomi Takeuchi et al. All Copyrigh t ©
2014 are guarded by law and by SCIRP as a guardian.
Tryptophan intake at breakfast has been known to be effective on promoting better mental health and
morning-typed life through serotonin and melatonin synthesis. For Japanese children, milk seems to be
important resource for taking tryptophan at breakfast because of limited meal time in the morning. This
study tries to show the effects of milk intake at breakfast on circadian typology and mental health of
Japanese infants aged 1 - 6 years. An integrated questionnaire was administrated to 1100 infants aged 1 -
6 years attending nursery schools or kindergarten in June 2012. Seven hundred and forty participants
(67.3%, 360 females and 380 males, mean age: 3.5 ± 1.4) answered the questionnaire. The questionnaire
included questions on sleep habits, the diurnal type scale by Torsvall and Åkerstedt (1980), questions on
mental health (anger and depression), and meals contents and time. Infants who took milk at breakfast
showed 21.2 (±3.4, n = 537) of the diurnal type scale scores on average which tended to be higher (more
morning-typed) than 20.7 (±3.5, n = 142) (p = 0.085) shown by those who did not take milk. Infants who
took carbohydrate (or carbohydrate and protein resource) plus milk at breakfast were significantly morn-
ing-typed than those who took only carbohydrate (or carbohydrate and protein resource) (p < 0.001). In-
fants who took milk at breakfast tended to be less frequently depressed than those who did not (p =
0.098). Taking milk at breakfast might be effective to promote serotonin synthesis in the morning
which could improve mental health directly and become “inner” zeitgeber for circadian clocks in in-
fants.
Keywords: Cow Milk in the Morning; Circadian Typology; Mental Health; Japanese Infants
Introduction
Breast-milk has been reported to have promoting effects of
sleep health in human infants. For example, Engler et al. (2012)
suggested that exclusively breast-fed infants had a significantly
lower incidence of colic attacks, lower severity of irritability
attacks, and a trend for longer nocturnal sleep duration due to a
questionnaire study. They reported that breast milk (nocturnal)
supplied substantial melatonin, while artificial formulas did not.
These results showed melatonin supplied to the infant via breast
milk might play a role in improving sleep and reducing colic in
breast-fed infants compared to formula-fed ones.
On the other hand, Cubero et al. (2005) also reported similar
results about circadian rhythms (daily fluctuation based on the
biological clock with period of about one day) of tryptophan
level in the breast milk of mothers and also 6-sulfatoxymela-
tonin circadian rhythm of the breast-fed infants. The tryptophan
in the breast milk presented a circadian rhythm with the acro-
phase (peak time) at around 03:00. This rhythm was followed
by the rhythm of the 6-sulfatoxymelatonin with the peak at
06:00 in the infants. This tryptophan intake might promote
sleep of them, and assumed sleep, actual sleep, and sleep effi-
ciency were significantly increased in the breast fed infants
compared with the formula fed infants. Sánchez et al. (2009)
reported that the nucleotides 5'AMP and 5'GMP in the human
*Corresponding author.
H. TAKEUCHI ET AL.
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173
breast milk showed circadian rhythms, the acrophases of the
first one being during the night, and of the latter one during the
day. Whil e 5'UMP did not show a clear circadian rhythm, there
was an increase in its levels at night. The rise in nocturnal le-
vels of 5'AMP, 5'GMP, and 5'UMP could be involved in in-
ducing the hypnoticaction of breast milk at night in the in-
fant.
How about has been reported the effect of cow’s milk on the
sleep and mental health (better mental healthmeans daytime
activity with better concentration, lower level of depression,
irritation and anger, well controlled emotion) of infants? Gues-
don et al. (2006) augured that cow’s milk has long been consi-
dered a relaxation beverage with sleep-inducing properties.
Already eighty years ago, it was reported that adults consuming
a meal of cornflakes and milk exhibited a stronger tendency to-
ward uninterrupted sleep (Laird & Drexel, 1934). Electroence-
phalography showed that sleep was significantly improved in
older people who fed a milk and cereal meal at bedtime (Bre -
zinova & Oswald, 1972).
Tryptophan intake at breakfast has been known to be effec-
tive on promoting better mental health and morning-typed life
through serotonin and melatonin syntheses (Harada et al., 2007;
Nakade et al., 2009, 2012; Wada et al., 2013). For Japanese
children, cow milk seems to be important resource for taking
tryptophan at breakfast because of limited meal time in the
morning. However, there have been no reports on the effect of
cow milk intake at breakfast on the effect of circadian typology
and mental health of human young children. This study aims to
answer the question from the epidemiological point of view.
Methods
Parti cipants
The data used was collected from responses to questionnaires
completed in June of 2012 by 740 parents (more than 95% are
mothers, response rate: 67.3%) of children aged 1 - 6 (360 girls
and 380 boys) in 10 city-run nursery schools and 1 kindergarten
affiliated to the Faculty of Education, Kochi University located
in Kochi city (33.3˚N).
Materials and Procedure
The questionnaires included The Diurnal Type Scale by
Torsvall and Åkerstedt (1980) and a revised version for child-
ren (Harada et al., 2007), questions on mental health of the
children (such as anger and depression) (Harada et al., 2007)
and question for children about breakfast contents. The version
for children (Harada et al., 2007) of the Diurnal Type Scale
(Torsvall & Åkerstedt, 1980) was used to objectively measure
diurnal preference. This part consisted of seven questions: three
pertaining to sleep onset, three to sleep offset and one to peak
timing of activity. Each question allows for choice (scored from
1 to 4) and the Diurnal Type Scale score was the sum of the
7 answers. Scores ranged from 7 to 28, with lower scores
representing evening-types and higher scores representing mor-
ning-types. The section of sleep habits consisted of questions
on sleep onset and offset timings on weekdays and weekends
and questions about the quality of sleep such as mood upon
falling asleep and waking up. The data was statistically ana-
lyzed using χ2-tests, Mann-Whitney U-tests, and Kruskal-Wal-
lis test with SPSS 12.0 statistical software. Diurnal Type Scale
scores were expressed as means plus or minus the standard
deviation (Mean ± SD).
The study followed the guidelines established by the Chro-
nobiology International journal for the conduct of research on
human subjects (Portaluppi et al., 2010). Before administrating
the questionnaires, each participant (parents or guardians) was
given a written explanation that detailed the concepts and pur-
poses of the study and stated that their answers would be used
only for academic purposes. After the above explanation, all
Table 1.
Relationship between whether Japan ese infants take cow milk (M) and/or produce made from cow milk (PM) at breakfast an d dinner and the diurnal
scale scores.
M and/or PM The Diurna l Type Scores One-Way ANOVA
mean s.d. n
Breakfast not taken 20.4 3.6 122 df = 1, F value = 3.49, p = 0.062
taken 21.1 3.2 323
Dinner not taken 20.9 3.3 311 df = 1, F value = 0.21,
taken 21 3.4 134 p = 0.607
M The Diurnal Type Scores One-Way ANOVA
mean s.d. n
Breakfast not taken 20.6 3.5 241 df = 1, F value = 3.46,
taken 21.2 3.1 204 p = 0.063
Dinner not taken 20.9 3.3 368 df = 1, F value = 0.45,
taken 21.1 3.6 77 p = 0.504
PM The Diurnal Type Scores One-Way ANOVA
mean s.d. n
Breakfast not taken 20.8 3.4 192 df = 1, F value = 0.41 ,
taken 21 3.3 253 p = 0.524
Dinner not taken 20.9 3.3 354 df = 1, F value = 0.04,
taken 21 3.3 91 p = 0.833
H. TAKEUCHI ET AL.
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174
parents (or guardians) agreed completely with the proposal. The
study was also permitted by the kindergarten nurses’ commit-
tees of the ten nursery schools and one kindergarten which
carried out an ethical inspection of the contents of the ques-
tionnaire. As the young children could not complete the ques-
tionnaires themselves, their parents or guardians completed
them on their behalf.
Results
Infants who took milk at bre akfas t showed 21.1 (±3.2 of SD, n =
323) of the diurnal type scale scores on average which tended to be
higher (more morning-typed) than 20.4 (±3.6, n = 122) (p = 0.06)
shown by those who did not take milk (Table 1).
Japanese infants taking only carbon hydrates (CH: in this
case mostly bread and beverage like as fruit juice, with or
without gas), carbon hydrates plus cow milk (CH + M), ca rbon
hydrates plus main dish (protein resources) (CH + MD: in this
case main menu is bread and boiled rice plus cooked eggs, ham
& sausage and fermented soybeans = Natto in Japanese, some-
times salmon flakes), carbon hydrates plus main dish plus cow
milk (CH + MD + M) showed mean ± SD of the diurnal type
scores of 19.0 ± 3.9, 20.6 ± 2.8, 21.0 ± 3.3, 21.3 ± 3.1, respec-
tively (One way ANOVA: df = 3 , F = 6.082, p < 0.001) (Figure
1). Infants who took carbohydrate (or carbohydrate and protein
resource) plus milk at breakfast were significantly morning-
typed than those who took only carbohydrate (or carbohydrate
and protein resource) (p < 0.001) (Figure 1).
Infants who took milk at breakfast tended to be less fre-
quently depressed than those who did not (χ2-test, χ2-value =
6.288, df = 3, p = 0.098) (Fig ure 2 ). Infants who took cow milk
at dinner showed less frequency to be anger with a small trigger
than those who did not so (χ2 test: χ2-value = 9.46, df = 3 p =
0.024) (Figure 3), and infants who took cow milk and/or prod-
uct made from cow milk at dinner showed again less frequency
to be anger with a small trigger than those who did not so (χ2
test: χ2-value = 10.56, df = 3, p = 0.014) (Figure 4). Morning-
typed infants showed less frequency to become anger with a
small trigger than those of medium- and evening-typed ones 2
test: χ2-value=10.71, df = 3, p = 0.013) (Figure 5).
Discussion
Tryptophan included in cow milk taken at breakfast might be
7
14
21
28
CH
CH+M
CH+MD
The diurnal type scale
M-type
E-type
Figure 1.
Several patterns of breakfast contents and the diurnal type scales in Japanese infants.
CH: carbon hydrates; CH + M: carb on hydrates plus cow milk; CH + MD: carbon hy-
drates plus main dish (protein resources); CH + MD + M: carbon hydrates plus main
dish plus cow milk.
Figure 2.
Relationship between whether Japan ese infants take milk at breakfast
and the frequency to be inactive (depressed).
0%20% 40% 60% 80%100%
朝牛乳不摂取
朝牛乳摂取
よくある
ときどきある
たまにある
ない
Milk at
breakfast
No milk
at breakfast
“How many frequently does your child become inactive (depressed)?
0 20 40 60 80 100 (%)
Frequently
Sometimes
Rare
Not at all
H. TAKEUCHI ET AL.
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175
Figure 3.
Relationship between whether Japanese infants take milk at dinner
and the frequency to be angry with a small trigger.
Figure 4.
Relationship between whether Japanese infants take cow milk and/or
a product made from milk at dinner and the frequency to be angry
with a small trigger.
0.0 25.0 50.0 75.0 100.0
M-type
Frequent
Sometimes
Rare
Not at all
Frequency to be
angry with a
small trigger
(%)
(χ2 test: χ2 value = 10.71, d f = 3, p = 0.013)
Figure 5.
Relationship between the frequency to be angry with a small trigger and
the circadian typolo gy. M-type: 21 - 28 scores of the diurnal type score;
Non-M-type: 7 - 20 scores.
effective on promoting better mental health and morning-typed
life through serotonin and melatonin synthesis like as other
protein resources of fermented soybeans, eggs, dried fishes,
hams and so on (Harada et al., 2007; Nakade et al., 2009, 2012;
Wada et al., 2013). For Japanese children, cow milk may be
important resource for taking tryptophan at breakfast because of
limited meal time in the morning.
Taking cow milk promoted the integrated health score con-
sisting of four issues on catching a cold, attack of fever, appe-
tite level, irritation and diarrhea in Japanese infants (Nakagawa,
1991). Intervention study for Japanese elementary school stu-
dents to which cow milk was supplied revealed that the after-
school supply of cow milk promoted the preference to take
breakfast and lunch (Ishii et al., 2012), and inter-classes supply
in the morning enhanced the concentration into classes after
taking cow milk (Ishii et al., 2011) compared with the control
group which has not been supplied. However, these physiolog-
ical and psychological positive effects of cow milk did not
mention about circadian timingof the milk supplement. This
study implies that the morning supplyof the cow milk is
important to promote both physical and mental health of child-
ren at first.
Taking milk (tryptophan and Vitamin B6 resource) at break-
fast might be effective to promote serotonin synthesis in the
morning which could improve mental health directly and be-
come “inner” zeitgeber for circadian clocks in infants.
Acknowledgements
We thank all the participants of this study. Thanks are also
due to the financial supports by Research Foundation by Japan
Dairy Associa tion (J-MILK) (2013-2014) (To T. HARADA).
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0%25% 50%75% 100%
摂らない
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Frequency to be angry
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Yes
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