The research reported in this article had two main aims. The first was to extend research on a well-established topic, the effects of breakfast on cognition, by examining associations between breakfast consumption and cognitive failures and accidents. A second aim was to investigate whether snacking also influenced these outcomes. The next section provides a brief overview of effects of breakfast.
Frequency of breakfast food consumption (e.g., cereal, dairy products, fruit and bread) is linked with a number of health benefits: better weight management; lower cholesterol; reduced risk of metabolic syndrome; better digestive functioning; fewer upper respiratory tract illnesses, and better mental health [1
]. Regular breakfast consumption is associated with higher intake of key vitamins and mineral [2
]. This may increase the likelihood of meeting nutritional requirements. Conversely, breakfast skippers may not make up for missed nutrients at other meals [4
]. Breakfasts containing ready-to-eat-cereal may also improve the diet due to fortification with micronutrients and low fat levels. Indeed, a review of breakfast and the diet of adults confirms that breakfast eaters consume better quality diets that include more fiber and nutrients and fewer calories than the diets of breakfast skippers [5
]. This has been confirmed in children and a review of 47 studies [2
] showed that breakfast eaters have higher daily intakes of fiber, calcium, vitamin A, vitamin C, riboflavin, zinc and iron compared to breakfast skippers. The 2005Dietary Guidelines for Americans
identify whole grains, fat-free and low fat milk and milk products, fruits and vegetables as “foods to encourage
”. Popular breakfast foods help people meet recommendations for these food groups. Breakfast also contributes to whole grain intake (over 30% of the intake) which is known to reduce the risk of diabetes and coronary heart disease. Milk is the most commonly consumed breakfast food (consumed by over 50% of people who eat breakfast at home) and this, again, helps to meet dietary recommendations for this type of food. Similar results have been reported for fruit intake, with fruit or fruit juice consumption at breakfast being linked with greater total fruit intake over the day [6
It is often thought that consumption of breakfast enhances performance, a suggestion which has arisen largely from a series of studies by Tuttle and colleagues over 40 years ago (“the Iowa Breakfast studies”). The main aim of these studies was to evaluate the effects of varying breakfast regimes on physiological performance but a number of the studies also included some tests of mental performance. In the first experiment of the series [7
], they compared the effects of four breakfast regimes: (a) a heavy breakfast, (b) a light breakfast, (c) no breakfast and (d) coffee only. Results showed that in the no-breakfast condition, there was a tendency towards slower reaction times. However, this was the only condition in which caffeinated coffee was not given and the results may reflect this. This was replicated when the same subjects were re-tested. Five out of six of the females showed a significant increase in simple reaction time in the no-breakfast condition, while three out of six showed a significant increase in choice reaction time in the same condition. Clearly results from studies with such a small number of subjects must be treated with caution.
They then carried out a similar experiment [8
] comparing breakfast and no-breakfast conditions, with testing taking place three hours after breakfast. Six of the ten subjects showed no change in reaction time in the no-breakfast condition (as compared to breakfast), three showed a significant increase in reaction times, while one subject’s reaction time increased significantly during the no-breakfast condition. Again, it is difficult to draw confident conclusions from such a study. Another study [9
] found no effect of breakfast on reaction times. Three breakfast conditions were compared: (a) bacon-egg and milk breakfast, (b) no breakfast, and (c) cereal and milk breakfast. Subjects (males aged 60 to 83 years) received the bacon-egg and milk breakfast for the first five weeks, followed by four weeks on no breakfast and four weeks on cereal and milk. Seven out of the eight subjects showed no change in reaction times during the course of the experiment. Although this experiment has the advantage that it examined the long term effects of breakfast, the small sample size, poor experimental design and the use of only a few measures of performance limits the value of the study.
These early studies have been criticized for having small numbers of subjects, for producing inconsistent findings and for the use of subjective assessments [10
]. The range of performance measures used was also small, being limited mainly to reaction time tasks. However, impaired performance associated with omitting breakfast was observed in other early studies with a variety of different types of breakfast. One study [11
] assessed visual and motor functioning 2 h and 3 h after the consumption or omission of breakfast. The results showed that these functions were impaired when breakfast was not eaten compared to when it was. Another study [12
] compared a standard breakfast with a no-breakfast condition. The volunteers were chosen so that half habitually ate breakfast and half no breakfast. A range of performance measures were employed: a visual search task, a short term memory task, vigilance task and a coding task. Testing was carried out in the late morning. Participants were tested on five occasions: once following their normal breakfast, twice following the standard breakfast and twice following no breakfast. A modified Latin-square design was used to balance order of conditions. The consumption or omission of breakfast did not alter performance. Rather, performance was most impaired when subjects changed from their normal meal. This led to the view that “the occasional omission of breakfast is more deleterious than the constant omission”.
Other research [13
] has compared the effects of no breakfast and consumption of a high protein drink on spatial memory and immediate recall of a word list. Half the subjects were habitual breakfast eaters and half did not usually eat breakfast. Consumption of the high protein drink increased the speed with which both memory tasks were completed. Further research [14
] has confirmed that breakfast improves aspects of memory and suggested that this may reflect several different mechanisms. Other studies have suggested that the size and composition of breakfast influence the post-meal response. One study [15
] compared low fat/high carbohydrate, medium fat/medium carbohydrate, high fat/low carbohydrate and no-breakfast conditions. No clear differences in performance were observed as a function of type of breakfast but subjects given the low fat/high carbohydrate breakfast (which was most similar to their normal meal) reported improved mood compared to the other conditions. More recent research [16
] has compared breakfasts that contained either high or low levels of carbohydrate, fat or protein. Better memory was found to be associated with consumption of meals that more slowly released glucose into the blood. This benefit of a low glycaemic index breakfast has been confirmed in animal studies [17
] and in children [18
The next section reports two studies [20
] which examined the effects of breakfast on mood and a range of different aspects of performance. The type of breakfast was manipulated and the influence of caffeinated drinks examined. The experiments also investigated whether personality, eating habits, gender and previous night’s sleep modified any effect of breakfast on behavior. The first experiment examined the effects of two types of breakfast on sustained attention tasks (i.e.
, tasks which show an effect of lunch), mood and cardiovascular functioning. Volunteers were given either caffeinated coffee or decaffeinated coffee after the meal (or no meal). This was done to investigate whether caffeine modified any effects of breakfast, and secondly, as a positive control to show that the tests used were sensitive to changes in state produced by caffeine [22
In the first study a between subject design was used and volunteers were assigned to one of the six conditions formed by combining the three breakfast and two caffeine conditions. Volunteers were either assigned to a no-breakfast condition, a cooked breakfast condition or cereal/toast breakfast. After breakfast participants were either given de-caffeinated coffee or de-caffeinated coffee with 4 mg/kg body weight of caffeine tablets added to it. The results showed that breakfast had no effects on performance of sustained attention tasks. In contrast, caffeine improved performance of these tasks. No interactions between breakfast conditions and personality were found in any of the analyses. Similar results were found when gender was included as a factor. Smith et al.
] examined effects of breakfast on performance of memory tasks. Consumption of breakfast improved recall and recognition of a list of words but had no beneficial effects on working memory or semantic memory tasks. Again, effects of breakfast were not modified by caffeine or by personality and gender. Breakfast had no effect on free recall in the late morning or after lunch, which suggests that the effects of breakfast on episodic memory are restricted to a few hours after the meal.
Smith, Clark and Gallagher [23
] extended the above results by showing that consumption of breakfast cereal may also improve spatial memory. However, the most robust effects of breakfast on memory are found in free recall tasks and these effects have been observed after consumption of high carbohydrate cereals and cereal bars [24
]. Similarly, a mid-morning cereal bar may also have beneficial effects when consumed after a small breakfast [24
There have been a few studies that have examined effects of breakfast in elderly adults. Early studies by Tuttle and colleagues found little evidence for an effect of breakfast on the cognitive function of the elderly. More recent studies have demonstrated both acute effects of breakfast and effects of breakfast habit. Kaplan et al.
] found that carbohydrate intake was associated with improved performance of a short-term memory task whereas a protein breakfast was associated with reduced forgetting in a paragraph recall task. Smith [27
] found that elderly adults, aged between 60 and 79 years, who ate breakfast cereal every day performed better on a test measuring intellectual functioning than those who consumed breakfast less frequently. It should be noted that this last result could reflect an effect of intelligence on breakfast consumption rather than a causal effect of breakfast consumption on intelligence. Further intervention studies are needed to assess the effects of breakfast on cognitive function in the elderly.
There have been a number of reviews of the effect of breakfast on the cognitive performance of adolescents and children [2
] and the main findings can be summarised as follows. There have been over forty studies published on this topic in the last 60 years (see [29
] for details of the literature). The results confirm the adult literature showing that breakfast has a beneficial effect on cognition, with the strongest support coming for improvements in memory. This effect is most readily apparent when nutritional status is compromised. Less is known about the effects of different types of breakfast and the role of breakfast size and composition requires further consideration. Wyon et al.
] reported that children did better on tests of creativity, physical endurance and mathematical ability when they consumed a high energy breakfast than when they consumed a low energy breakfast. Michaudet al.
] confirmed these results using a short-term memory task. Other studies [28
] have shown that an oatmeal breakfast led to better performance (especially in girls) than ready-to-eat cereal. Most studies have investigated children rather than adolescents. A recent study of high school students [32
] showed that breakfast had no effect on sustained attention but improved visuospatial memory in males. Studies of school breakfast programmes suggest that such interventions can have positive effects which may reflect an effect of the programmes on school attendance.
Little is known about the real-life behavioral implications of consuming breakfast for adults. For example, a literature search revealed no information on breakfast and accidents and errors at work (or outside of work), road traffic accidents or driving performance, or on productivity at work. Recent research on caffeine has moved from the laboratory to epidemiological studies of consumption and human error and accidents. Smith [33
] examined the impact of habitual caffeine consumption on performance and safety at work. The study involved secondary analyses of a database formed by combining the Bristol Stress and Health at Work and Cardiff Health and Safety at Work studies. In the first analyses associations between caffeine consumption and frequency of cognitive failures were examined in a sample of 1253 white-collar workers. The second set of analyses examined associations between caffeine consumption and accidents at work in a sample of 1555 workers who were especially at risk of having an accident. The results from the study demonstrated significant associations between caffeine consumption and fewer cognitive failures and accidents at work. After controlling for possible confounding factors it was found that higher caffeine consumption was associated with about half the risk of frequent/very frequent cognitive failures and a similar reduction in risk for accidents at work. Overall, the results confirmed that caffeine consumption may have benefits for performance and safety at work.
] conducted secondary analyses of a large epidemiological database to examine associations between caffeine consumption and cognitive failures (errors of memory, attention and action) in a non-working sample. Associations between caffeine consumption and physical and mental health problems were also examined. After controlling for possible confounding factors significant associations between caffeine consumption and fewer cognitive failures were observed. Overall, the results show that caffeine consumption may benefit cognitive functioning in a non-working population. This confirms earlier findings from working samples. This beneficial effect of caffeine was not associated with negative health consequences. This approach of examining associations with cognitive failures and accidents was used here to examine possible beneficial effects of consuming breakfast. When one is investigating a new topic it is sensible to also try and replicate established findings. Breakfast consumption has also been associated with lower levels of stress [35
] and this was also examined here.
Recent research has examined the effects of snacking on well-being [38
]. Little of this research has focused on cognitive functioning although there is evidence that “grazing” (eating a little but often) leads to better performance than consuming a smaller number of large meals [41
]. In contrast to breakfast, where frequency of consumption rather than type of breakfast appears to be the most important factor, snacking frequency has less influence than type of snack. Research by Chaplin [42
] has shown that snacks that are perceived as being unhealthy (chocolate, crisps, and biscuits-all perceived as unhealthy by over 80% of the sample) are associated with lower well-being scores. The second aim of the present research was to examine associations between this type of snacking and cognitive failures, accidents and stress.
Breakfast consumption and unhealthy snacking showed significant associations with stress, accidents, minor injuries and cognitive failures at work. The reduced stress levels reported by breakfast consumers and the higher levels associated with unhealthy snacking confirms previous findings. Previous research had identified smoking, alcohol consumption, sleep problems, age and gender to be associated with accidents and injuries. Dietary factors, particularly breakfast and unhealthy snacking, were still strongly associated with accidents, injuries and cognitive failures while controlling for these other variables. Regular breakfast consumers were half as likely to have an accident or minor injury at work as irregular breakfast consumers. This possibly reflects the less frequent cognitive failures at work reported by breakfast consumers. High consumption of unhealthy snacks was associated with twice the likelihood of having a minor injury at work and also outside work. Although it is not clear how breakfast and unhealthy snacking affect accidents, injuries and cognitive failures, it is a relationship which warrants further attention and investigation. Increasing breakfast consumption and reducing unhealthy snack consumption could be used as the basis of a simple and cost effective intervention for health and safety in the workplace.
Only a few of the potential confounders were controlled for in the current study and more research is needed to explore the associations between breakfast and unhealthy snacking. It is not possible to draw any firm conclusions about the mechanisms by which breakfast and snacking may influence accidents and injuries. One possible explanation is that high fat meals have been found to increase fatigue and decrease alertness [50
]. Unhealthy snacks are generally high in fat, while most breakfast cereals are low in fat. In addition breakfast cereal and toast have been found to be associated with increased alertness. Other factors which have been shown to be associated with accidents and injuries also need to be taken into consideration for example stress and fatigue levels. Cognitive failures are lapses in concentration and attention and may also be affected by fatigue and alertness. All of these results were found while controlling for demographic factors and health related behaviors. Gender, age, smoking, alcohol consumption and difficulty sleeping were included for all of the analyses. These results imply that the positive associations between breakfast and health outcomes are not simply a reflection of the positive effects of a healthy lifestyle. Unhealthy snacking was negatively associated with health and well-being in the current sample. It also appears that unhealthy snacking is not just an indicator of an unhealthy lifestyle per se
. Due to the cross-sectional nature of the study it is not possible to make any conclusions about causation and directionality. However it is unlikely that having an accident influences dietary intake. Intervention studies are required to properly explore the relationships between breakfast frequency, snacking frequency and snacking type, and health and well-being.
The current sample only considered working health professionals, predominantly nurses and therefore was homogenous. The vast majority of the individuals in this sample were white females who did not smoke and only consumed small to moderate amounts of alcohol. Therefore the conclusions drawn from the current study cannot be generalized to other groups. The associations between snacking type and health and well-being need to be replicated in a general public sample. In addition vulnerable groups, for example children and the elderly should be considered as they may receive the most benefit from any interventions. Breakfast and unhealthy snack food consumption exhibit strong associations with human error and well-being. This was still found to be the case when controlling for other lifestyle and demographic factors which were associated with health outcomes. The beneficial effects of breakfast were found for accidents, minor injuries and cognitive failures in the workplace. Increasing breakfast consumption may be the basis of an intervention programme to improve health. In contrast, unhealthy snacking was largely associated with non-work outcomes and changing these may influence cognition and well-being in such contexts.