Friday July 1 2011
The study did not assess sweet-eating habits over time
“Sweets are ‘good for children and may stop them getting fat in later life’,” reported the Daily Mail.
This news story is based on a US study that assessed the diet of more than 11,000 children and adolescents over 24 hours. Researchers looked at how their confectionery consumption was related to their total energy consumption, body fat and other measures of heart health, such as blood pressure and blood fats. Those who ate sweets or chocolate were found to have higher total energy and added sugar intake, but were also less likely to be overweight or obese.
The study has numerous limitations which seriously limit the conclusions that can be drawn. In particular, the study took only a one-off measurement of the children’s sweet and chocolate eating habits at a single point in time, which means it cannot show how eating them affects weight or other factors over time. Also, as it only looked at the children’s diet for 24 hours, it tells us little about their longer-term eating habits. The children’s activity levels were not clearly reported, and may have been higher in the confectionery eaters.
Most importantly, no assumptions should be made about longer-term heart health or body weight, and it should not be concluded that children and adolescents who eat sweets or chocolate will be at lower risk of getting fat in later life or at lower risk of heart disease. The numerous health benefits of a balanced diet and regular exercise are well established.
Where did the story come from?
The study was carried out by researchers from Louisiana State University Agricultural Center, Nutrition Impact, and Baylor College of Medicine in Houston, USA. Funding was provided by the USDA Agricultural Research Service, with partial support from the US Department of Agriculture, and the National Confectioners Association. The funders were reported to have no role in the study’s design or analysis, or in writing the paper. The study was published in the peer-reviewed journal Food & Nutrition Research.
The Daily Mail did not mention the main limitations of this study, which mean that few conclusions can be made from it. Most importantly, there is no evidence from this study to support the statement that “sweets may stop [children] from getting fat in later life”.
What kind of research was this?
This study aimed to determine the effect of eating confectionery on children’s health. The researchers looked at the relationship between chocolate or sweet consumption in children and adolescents and their dietary intake of calories, fat and added sugar, their overall dietary quality, their body weight and fat measures, and their risk factors for cardiovascular disease.
This was a cross-sectional study, in which a “snapshot” of data is taken at one point in time. The results, therefore, cannot show whether sweet or chocolate consumption affects weight or other factors over time. Current confectionery intake at one point in time can also tell us nothing about longer-term confectionery-eating patterns. Most importantly, no assumptions can be made about future body weight or cardiovascular disease from the current study.
What did the research involve?
This study included 11,182 children and adolescents (aged 2-18 years old) who took part in the 1999-2004 National Health and Nutrition Examination Surveys (NHANES). Automated interviews were used to assess dietary intake over the past 24 hours (parents recalled food intake for children aged five and under, children and parents recalled intake for children aged 6-11, and adolescents aged 12 and over contributed data themselves). The different food types were allocated codes from The Survey Nutrient Databases.
Consumers of sweets and chocolate were defined as those who consume any amounts of confectionery (except gum) and were placed in one of three categories: those eating any type of confectionery, those eating chocolate bars, and those eating sweets. The data were also used to assess the children’s total energy intake, total fat and saturated fatty acid intake. The Healthy Eating Index-2005 (HEI-2005) was used to determine overall quality of the diet. The researchers also collected measures of waist circumference, weight, height, blood pressure, and blood fat levels from the participants.
The researchers then looked at body weight measures, dietary quality and cardiovascular risk factors for each confectionery intake group compared to children who did not eat confectionery. The analyses took into account various factors that could affect results, including sex, age, ethnicity and energy intake. Some analyses also took into account children’s reported physical activity.
What were the basic results?
The researchers assessed 7,049 children aged 2-13 years old and 4,132 adolescents aged 14-18. About a third of children and adolescents ate sweets and chocolate on the day that they filled out the questionnaire, and consumption was more common among girls than boys.
In the 24 hours before they filled out the questionnaire, children aged 2-13 years old consumed an average of 11.4g of confectionery, of which 4.8g were chocolate and 6.6g were sweets. In the same period, adolescents aged 14-18 years old consumed an average of 13g confectionery overall, including 7g of chocolate bars and 5.9g of sweets. Those who ate confectionery had higher total energy intake (2,249kcal) than those who did not eat any confectionery (1,993kcal), and also had higher total added sugar intake (28g and 23g respectively).
The researchers found that the average HEI-2005 score of dietary quality was no different between those who ate confectionery and those who did not, or in those who ate sweets and those who did not. However, dietary quality was significantly lower in those who ate chocolate bars compared to those who did not.
Body mass index (BMI) and waist circumference were lower in those who ate confectionery (BMI 19.5) compared to those who didn’t (BMI 20.1). This result remained significant after the researchers took into account age, gender, ethnic group and overall energy intake. The researchers reported that if they took into account the children’s self-reported moderate or moderate-to-vigorous activity levels, the results did not change, but the fully adjusted results were not provided in the research paper.
After the researchers took into account the same factors, the odds of being overweight or obese were lower among those who ate confectionery than among non-consumers. Compared to non-consumers, the odds of being overweight were 22% lower in consumers of confectionery (odds ratio [OR] 0.77, 95% confidence interval [CI] 0.68 to 0.90), and the odds of being obese were 26% lower in consumers (OR 0.74, 95% CI 0.66 to 0.82). The effects on these results of taking into account a child’s physical activity were not reported in the research paper.
There was no difference in cardiovascular risk factors (such as blood pressure and blood fat levels) between confectionery consumers and non-consumers.
How did the researchers interpret the results?
According to the researchers, their results suggest that eating sweets and chocolate does not adversely affect health-risk markers in children and adolescents.
This study assessed a large sample of 11,182 children and adolescents in the US. They were asked to recall their diet in the past 24 hours, which the researches then looked at in relation to factors such as body weight and measures of cardiovascular health, including blood pressure and blood fat levels. However, despite the study’s large size, only limited conclusions can be drawn from the results.
Overall, the researchers found that, as expected, children who ate confectionery in the previous 24 hours had higher total energy and higher added sugar intake compared to those who ate no confectionery. Unexpectedly, they found that overall dietary quality was no different between those who ate confectionery and those who did not. Also, confectionery eaters were less likely to be overweight or obese. However, the reasons for these unexpected results, particularly why children who ate sweets and chocolate had lower weight, cannot be determined. It should not be assumed that children will be healthier or weigh less if they eat confectionery.
There are some important limitations to be considered:
- This cross-sectional analysis used a one-off assessment of dietary intake in a single 24-hour period, then related this to current measures of body health. Such an analysis cannot prove cause and effect, as it cannot show how sweet and chocolate consumption over time affects weight or cardiovascular risk in the future.
- Intake of confectionery in the past 24 hours may not reflect longer-term dietary patterns. For example, while the study found that children who reported eating confectionery were less likely to be overweight, it is not known whether a child who ate no confectionery in the past 24 hours normally doesn’t eat any, or whether they eat it regularly but didn’t on the previous day.
- A child or parent who knows the child is overweight may underestimate or deny the child’s confectionery consumption because they don’t want people to think that the child has unhealthy eating habits. Also, children who are overweight or obese may be on diets that restrict their sweet and chocolate consumption.
- Although the study assessed the children’s self-reported physical activity levels and took these into account in the analyses of BMI, it was not clear exactly how the researchers did this. The balance between total energy intake and physical activity is a key factor that can affect a person’s weight.
- Finally, the researchers took into account children’s total energy intake in their analyses of the relationship between overweight and obesity and confectionery intake. Making these sorts of adjustments usually helps remove the effects of other factors that may influence results. However, if eating sweets affects the risk of being overweight or obese by increasing children’s total calorie intake, removing the effect of total calorie intake in this way is likely to lead to an underestimation of the effect of eating confectionery on overweight and obesity.
Most importantly, no assumptions should be made about the longer-term cardiovascular health or body weight of children who eat confectionery. It should not be concluded that children and adolescents who eat sweets or chocolate will be at lower risk of getting fat in later life or at lower risk of cardiovascular disease. The numerous health benefits of a healthy balanced diet and regular exercise are well established.