PEDIATRICS Vol. 122 No. 2 August 2008, pp. 279-284 (doi:10.1542/peds.2007-0944)
ARTICLE |
Influence of Having Breakfast on Cognitive Performance and Mood in 13- to 20-Year-Old High School Students: Results of a Crossover Trial
a Centre for Neuroscience and Learning
b Institute of Epidemiology, Ulm University, Ulm, Germany
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ABSTRACT |
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 TOP ABSTRACT METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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OBJECTIVE. The goal was to determine whether breakfast had effects on the cognitive performance and mood of high school students.
METHODS. A crossover trial was performed in boarding schools, involving 104 students between 13 and 20 years of age. The participants were randomly assigned to 2 equal-size groups on the morning of the first testing day. One half of the total sample received a standardized breakfast, whereas the other half received no breakfast. Seven days later, the treatment order was reversed. Measurements of cognitive function included standardized tests of attention and concentration, as well as tests of verbal and spatial memory. In addition, mood was rated with a self-administered questionnaire covering the dimensions of positive and negative affect, information uptake, arousal, and alertness. Statistical analysis consisted of repeated-measures analysis of variance.
RESULTS. Breakfast had no effect on sustained attention among high school students. Visuospatial memory was improved in male students. Self-reported alertness improved significantly in the entire study population. Male students reported feeling more positive after consuming breakfast, compared with the fasting condition.
CONCLUSIONS. This crossover trial demonstrated positive short-term effects of breakfast on cognitive functioning and self-reported alertness in high school students.
Key Words: breakfast • high school students • cognitive function • mood
Abbreviations: VGZ—Verfahren zur Erfassung des Gefühlszustandes • d2—Aufmerksamkeits-Belastungs-Test • LGT-3—Lern- und Gedaechtnistest
Breakfast is often labeled the most important meal of the day, and parents and educators usually stress the importance of breakfast consumption as a prerequisite for successful learning after the long nightly fasting period.1 Observational studies have shown, however, that children and adolescents skip breakfast more often than any other meal.2 Omission of breakfast is highly prevalent in the United States and Europe (rates: 10%–30%).2,3 Skipping breakfast is more prevalent among female students, children from lower socioeconomic backgrounds, and older children and adolescents.2,3
The time between the evening meal and breakfast the next morning is usually the longest period without uptake of energy and nutrients. Extending this fasting episode by omitting breakfast may result in metabolic changes that interfere with aspects of cognitive functioning and school performance. Missing breakfast may impair the availability of energy (glucose) or certain nutrients necessary for the synthesis of neurotransmitters, which in turn are necessary for correct functioning of the central nervous system.4,5
Although experimental, quasiexperimental, and field studies have been trying to determine the value of breakfast consumption for >50 years, a review concluded that evidence in support of breakfast is equivocal.6 Although several studies observed positive effects of breakfast consumption on speed and accuracy when visual and auditory short-term memory, immediate recall, delayed recall, and spatial memory were tested,7–10 others did not find significant effects.11–16 Only a few studies found effects on tasks requiring attention.7,17 Methodologic factors such as differences in study design,1,18 study populations,1 and testing instruments and testing procedures, possibly assessing different aspects of a single cognitive function,1,4 might have contributed to the observed inconsistencies.
Experimental and quasiexperimental study designs have been used to detect short-term effects of breakfast omission. Experimental studies were typically performed on wards or in laboratory-like settings and aimed to control for potential confounders such as meal composition and timing, duration of the nightly fasting period, and physical activity.9,19,20 Quasiexperimental studies had some of the features of experimental designs but did not usually control for confounders.11,18
With our study, we intended to make a contribution to the ongoing discussion about the benefits of breakfast consumption with respect to cognitive performance and mood among high school students. We chose to conduct the study in boarding schools, which allowed the students to remain in their familiar environment. At the same time, it was possible to control study conditions such as breakfast composition and consumption and sleep duration.
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METHODS |
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Participants and Field Work
All students
13 years of age who were attending 2 boarding schools in southern Germany on full board (ie, who lived on the campus) were invited to participate (N = 240). Parents and students were asked for informed consent. One hundred four subjects (43%) participated in the study. At baseline, all participants completed a short questionnaire on usual breakfast habits. The study was approved by the ethics committee of Ulm University.
Intervention
Participants were randomly allocated to 2 groups. According to the crossover design, each participant was tested twice, once with and once without having breakfast, 7 days apart. All participating students were encouraged to eat their regular dinner in the evening before the start of the study but were instructed not to eat after dinner. Drinking water was permitted.
The next morning, all participating students were awoken according to their regular schedule. Subjects allocated to the breakfast group received a standardized breakfast, consisting of 60 g of whole wheat bread, 20 g of butter, 20 g of nougat spread (Nutella, Frankfurt, Germany), and 30 g of strawberry jam, between 7:30 AM and 8:00 AM. The nutritional composition was as follows: carbohydrates, 992 kJ; protein, 103 kJ; fat, 895 kJ. Water and unsweetened peppermint tea were offered ad libitum. Students were asked to consume the whole breakfast. To avoid eating, fasting participants were separated from their eating peers. All meals were prepared by the school kitchen and served according to schedule in the school dining room.
Assessment of Cognitive Functioning and Mood
Cognitive testing of all participants started at 8:15 AM and was completed by 10:15 AM (Fig 1). The test battery started (time 1) with a short questionnaire for the assessment of mood, that is, the Verfahren zur Erfassung des Gefühlszustandes (VGZ) (Mood Assessment Scale) described by Feist and Stephan.21 It was followed by a test of sustained attention, the Aufmerksamkeits-Belastungs-Test d2, (Test of Attention d2) described by Brickenkamp,22 and a learning and memory test, the Lern- und Gedaechtnistest (LGT-3) (Learning and Memory Test-3) described by Bäumler.23 At the end of the testing session, students were asked to complete the questionnaire on mood a second time. The staff members administering the tests were blinded to the breakfast condition of the participants.
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Cognitive Functioning
Sustained Attention
The d2 test22 is a standard instrument for measuring concentration speed and attention (cancellation test). The items are composed of the letters "p" and "d" marked with 1, 2, 3, or 4 dashes. The subjects are given 15 seconds to scan each of 14 lines (658 items in total) and mark all entries of "d" with 2 dashes. Measures of performance include the total number of items processed, concentration performance (number of correctly marked relevant items minus number of incorrectly marked irrelevant items), and number of errors (number of incorrectly marked or missed items). A practice run preceding the d2 test familiarized the participants with the test procedure on both testing days (week 1 and week 2).
Learning and Memory
The LGT-3 described by Bäumler23 is a standardized test assessing learning capacity and immediate memory. The paper-and-pencil test consists of 6 subtests. In the trail subtest, subjects must memorize a route on a street map. In the retrieval phase, the subjects are presented with the map only and are asked to fill in the trail. In the objects subtest, 20 simple drawings, such as a ball, are presented. In the retrieval phase, the remembered drawings must be named. In the logos subtest, 20 logo-like figures, each consisting of a central icon and a frame, are presented. In the retrieval phase, each of the central icons is presented with the choice of 4 similar frames, and the subjects must identify the frame presented with the specific icon during the learning phase. In the telephone numbers test, 13 telephone numbers and corresponding extensions are presented. During retrieval, the extensions are presented without the corresponding number, and each extension must be matched with the correct number. In the Turkish vocabulary subtest, 20 German words and the corresponding Turkish expressions are presented for learning. During retrieval, each German word is presented with a choice of 5 Turkish words, and the correct Turkish word must be identified (none of the participants had any knowledge of the Turkish language). In the cued recall subtest, subjects are given a text containing information about the construction of a library. In the retrieval phase, subjects must answer questions about facts mentioned in the text.
The results of the subtests are summarized in the following 3 categories: total score (all 6 subtests), visuospatial memory (trail and logos subtests), and verbal memory (Turkish vocabulary, telephone numbers, and cued recall subtests). The subtests are presented individually on paper during the learning session. Memory recall is assessed immediately after the learning phase for all subtests.
Mood
The VGZ is a self-administered questionnaire assessing how participants "feel at the moment."21 Subjects were asked to rate 15 items in relation to their mood. The items were clustered into the 5 dimensions of negative affect (depressed, unhappy, and queasy), positive affect (happy, well, and cheerful), information uptake (fascinated, interested, and uninterested), arousal (calm, nervous, and agitated), and alertness (tired, sleepy, and awake). All answers were given on a 5-point rating scale ranging from not at all to very much.
Statistical Analyses
Analyses consisted of repeated-measures analysis of variance with breakfast condition (breakfast or no breakfast) as a within-subject variable and group (order of testing) as between-subject factors. Analyses were performed for the entire study population and for male students and female students separately. Because of a deviation from the standard testing protocol, 34 students were excluded from the analysis of d2 test results. All calculations were performed by using SAS 9.1 (SAS Institute, Cary, NC).
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RESULTS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Study Sample
The sample consisted of 54 male students and 50 female students in the age group of 13 to 20 years (mean: 17.2 ± 1.6 years) (Table 1). The students attended grades 8 to 13. Eighty-eight percent of the participants were regular breakfast eaters, defined as consuming breakfast
5 times per week.
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Sustained Attention
Concentration performance after breakfast approached significance (F = 2.81, P = .098) when the whole study population was considered (Table 2). However, there was a significant breakfast-group interaction for concentration performance (F = 134.73, P < .001). Breakfast had no effect on total numbers of items processed or error numbers. When results were stratified according to gender, neither male students nor female students benefited from consumption of the morning meal.
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Learning and Memory
The total memory score was not affected by breakfast in the whole study population. When results were subdivided into verbal and visual spatial memory scores, we observed a main breakfast effect on visuospatial memory for the whole study population (F = 4.95, P = .028).
When results were stratified according to gender, we observed a breakfast effect on visuospatial memory for male students only (F = 5.38, P = .024); however, there was a breakfast-group effect (F = 4.72, P = .035) (Table 3). For verbal memory, no effect of breakfast on the entire study population was observed. When results were stratified according to gender, there was only a tendency for improvement in female students (telephone numbers subtest), reaching borderline statistical significance (F = 2.8, P = .099). However, we also observed a breakfast-group effect (F = 28.36, P < .001) (Table 3).
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Mood
Consumption of breakfast showed positive effects on the mood of the study population. Intake of breakfast caused improvements in positive affect (time 1: F = 6.00, P = .016; time 2: F = 2.81, P = .097), information uptake (time 1: F = 2.89, P = .094), and alertness (time 1: F = 8.68, P = .004; time 2: F = 12.15, P < .001) and a decrease in negative affect (time 1: F = 4.49, P = .037) in the entire study population. Stratified analyses showed that improvements in positive affect (time 1: F = 10.92, P = .002; time 2: F = 8.41, P = .006) and information uptake (time 1: F = 6.83, P = .012) were mainly seen in boys. Alertness was clearly increased after breakfast in girls (time 1: F = 6.35, P = .015; time 2: F = 12.34, P = .001). Boys, however, showed only a tendency toward improved alertness (time 1: F = 3.25, P = .078; time 2: F = 2.81, P = .100) and decreased negative affect (time 1: F = 3.08, P = .085) (Table 4).
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DISCUSSION |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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With an increasing number of children and adolescents skipping breakfast, there is a need for scientific studies evaluating whether omission of breakfast affects the cognitive functioning and mood of fasting students. The results of our study showed beneficial effects of breakfast on short-term memory and mood but not sustained attention in adolescents and young adults.
When interpreting the findings, it is important to keep in mind the strengths and limitations of our study. Participants were provided with a standardized breakfast that was very typical of what most students this age in Germany would choose. However, deviations from the habitual nutritional intake, which might have affected cognitive performance8 and mood,4,24,25 cannot be ruled out. The study population included students 13 to 20 years of age, and existing data suggest that younger children might be more susceptible to brief fasting periods.1,8,15 Clearly, the students were not blinded to the intervention, and information bias cannot be fully excluded. In addition, we did not include measurements of biomarkers (eg, blood glucose levels). However, the sample size of our study was relatively high, in comparison with other well-controlled intervention studies. Most importantly, students were tested in their familiar school environment, where it was possible to control for many potentially confounding factors.
To our knowledge, only one other study was conducted in a setting similar to ours.11 The objective of Dickie and Bender,11 however, was to investigate the effects of breakfast omission on the mental performance of subjects who regularly ate breakfast. In a crossover design, the performance of 108 students 16 to 17 years of age was assessed by using 2 short-term memory tasks,26 a simple addition test,27 and an attention-demanding, sentence-verification test,28 3 hours after breakfast. In contrast to our results, the authors observed no difference in performance between breakfast and no-breakfast conditions and concluded that breakfast is either unimportant, or the tests employed were not sufficiently discriminating to detect the effects of omitting breakfast.11 In addition, Dickie and Bender11 did not report whether a standardized breakfast was provided and whether the actual nutritional intake of the participants was recorded.
Our study showed no improvements in speed and accuracy in a task requiring sustained attention for 
5 minutes. When studied on a metabolic ward, well-nourished children 9 to 11 years of age performed better on an attention-demanding task after having breakfast.17 In a study conducted by Wesnes et al,7 eating cereal for breakfast significantly improved the attention of 9- to 16-year-old students. Others failed to find positive effects. Smith et al9 in a study with adults (university students), as well as Lopez et al13 in a study with children 8 to 11 years of age from low socioeconomic backgrounds, found no differences produced by breakfast intake.
In line with some previous publications, we observed positive effects of breakfast consumption on memory functions.7,8 Interestingly, the observed benefits differed between male students and female students. Whereas visuospatial memory function of male students benefited significantly from breakfast consumption, the effect on memory function for female students was less pronounced and involved only the telephone numbers subtest of the verbal memory category. Unfortunately, only 1 previous publication reported findings stratified according to gender. Mahoney et al8 observed that girls 9 to 11 years of age but not boys showed improved short-term memory function in a digit span task after they ate oatmeal, compared with a ready-to-eat cereal or no breakfast.
This study confirmed and extended previous work on the effects of breakfast on the mood of schoolchildren. In assessments performed 15 and 120 minutes after breakfast, participants reported increased alertness. Furthermore, we observed differences between the genders. Male students and female students reported being more alert; in addition, boys felt more positive and were more interested after consuming breakfast. Wesnes et al7 also reported increased alertness in children after consumption of 2 types of ready-to-eat cereals. The study conducted by Mahoney et al8 found no effects of breakfast on alertness among 9- to 11-year-old children. In contrast, younger children (6–8 years of age) felt more alert after eating ready-to-eat cereal or oatmeal than before eating breakfast.
Evidence indicates that macronutrient composition might influence mood by affecting the synthesis of monoamine neurotransmitters.6 It has been suggested that carbohydrate-rich meals lead to increased fatigue and decreased alertness, whereas meals rich in protein increase alertness and decrease drowsiness.24,29 Because of the complex nature of the breakfast provided in this study, we have no evidence that the observed changes in mood were related directly to the nutritional composition of the meal.
The comparability of breakfast studies is limited. Besides differences in study design, in the nutritional composition of the meal, and in testing instruments evaluating different aspects of a single cognitive concept, the age of the participants might be an important factor.
Two studies published by Benton and colleagues30,31 indicated that children and adults react differently to an extended fasting period. Whereas children who had eaten a small breakfast benefited most from a midmorning snack,30 a small breakfast caused a more-positive mood than a more-substantial breakfast in a study with adults.31 These findings might reflect different metabolic requirements, which must be met with specific dietary provisions to ensure optimal neural functioning. Indeed, the brain of a child is relatively larger and more metabolically active than the brain of an adult. The rate of glucose utilization for a given amount of brain tissue in 4- to 10-year-old children is twice that of the adult brain; the rate then starts to decline, reaching adult levels at 16 to 18 years of age.32 Therefore, meal composition and frequency could affect children, adolescents, and adults differently.
After the overnight fast, breakfast might affect some aspects of cognitive performance directly by providing energy and precursors for the synthesis of neurotransmitters. Breakfast might affect cognitive performance indirectly through changes in mood caused by the macronutrient composition of the meal. Alternatively, if breakfast is consumed with other students or with family members, then the social interaction might lead to increased alertness, a prerequisite for the successful completion of cognitive tasks.
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CONCLUSIONS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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This randomized trial demonstrated positive short-term effects of breakfast on cognitive functioning and self-reported alertness in high school students. The observed differences according to gender and potential mediating effects between mood and cognitive performance deserve further investigation.
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ACKNOWLEDGMENTS |
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We thank the students, the teachers and the kitchen staff for their participation and cooperation in this study. Particular thanks are due to the late Stephan Weiland for the discussions, his enthusiasm and the critical reading of the manuscript.
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FOOTNOTES |
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Accepted Nov 13, 2007.
Address correspondence to Katharina Widenhorn-Müller, PhD, Centre for Neuroscience and Learning, Ulm University, Beim Alten Fritz 2, D-89075 Ulm, Germany. E-mail: katharina.mueller{at}znl-ulm.de
This trial has been registered at www.clinicaltrials.gov (identifier NCT 00556868).
The authors have indicated they have no financial relationships relevant to this article to disclose.
| What's Known on This Subject The results of existing studies on the effects of breakfast on cognition (memory and attention) and mood are inconsistent because of different study designs and study populations.
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| What This Study Adds When tested in a familiar environment (boarding school) under well-controlled conditions, students benefited from breakfast consumption. Different aspects of memory and mood were improved. In addition, we observed differences between the genders.
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PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics
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