Abstract
Background and aim
In 2007, the Danish Food Industry Agency announced a project where Danish schools could apply for funds to establish a school food programme to provide the school children with free school meals for two months during 2008. This school food programme should be tested and evaluated. The present PhD thesis is based on evaluation of the dietary effect of this project.
There is room for improvement of the dietary habits of Danish children. Dietary habits are influenced by multiple factors across different contexts. The school setting is known as a suitable arena for promotion of healthy eating. In Denmark most children eat a packed lunch brought from home.
It is challenging to collect dietary data from a pediatric population where recall problems exist and estimation of portion sizes can be complicated. Thus, to measure and assess the dietary effect of an intervention, new valid methods are needed.
The overall aim of this PhD thesis was to evaluate the dietary effect of a school food programme in Danish schools on the quality of lunch consumed by children aged 7-13 years compared to packed lunches brought from home. Furthermore, the aim was to develop appropriate methods to measure and assess dietary intake for evaluation of interventions, which are designed to promote credible evidence to this area. The objectives were; to evaluate the validity and reliability of a digital photographic method (DPM) to assess the quality of dietary intake from packed lunches brought from home among children aged 7-13 years (paper I); to develop and validate an index for assessment of dietary quality of school meals, either brought from home or provided by the schools (paper II); to evaluate the effect of implementing a school food programme on the dietary quality of lunches consumed by students aged 7-13 years compared to packed lunches brought from home and furthermore to investigate if a possible effect would differ between the youngest school children and the older (paper III).
Methods
The evaluation of the school food programme was conducted in 4 intervention schools and 4 control schools from all over Denmark. Data on packed lunches were collected at baseline. At 1st follow-up the children in the intervention schools were offered free school meals and at the 2nd follow-up the school meals were paid. The control group had packed lunches at all measurements. Collection of data covered 3 consecutive days during a week at each of the three measurements. In total 984 school children were invited at baseline – 493 from the 2nd -3rd grades and 491 from the 5th-6th grades. A standardized DPM was used to collect data on food intake 3 consecutive days in a week at all of the 3 measurements. To assess the dietary quality of food consumed a Meal Index of dietary Quality (Meal IQ) was developed.
The validity and reliability of the DPM was tested on weighed foods of 191 packed lunches. The Meal IQ was developed and validated against calculated nutrient content of both 191 packed lunches and 63 school meals.
Results
Implementing a school food programme increased the quality of dietary intake among school children aged 7-13 years at 1st follow-up where the school meals were free, compared to the packed lunches brought from home (P=0.004). At the 2nd follow-up, where the school meals were not provided for free, only a limited number of children ate school meals and there was no difference in quality of dietary intake at lunch among children in the intervention and control schools (P=0.343). The statistical analyses demonstrated some differences in changes in dietary quality intake at lunch between school children in the 2nd-3rd grades and 5th-6th grades. This was not due to different effect of the school food programme but was mainly explained by more skipped meals in the oldest age group compared to the youngest age group.
Correlation coefficients and cross-classifications between the DPM and the weighed foods showed good agreement. There were no statistical differences between fish, fat, starch, whole grains and Meal IQ using the two methods. Differences were found for fruit and vegetables. Bland-Altman analyses showed a tendency to underestimate high amounts of these variables using the DPM. For inter-rater reliability, Kappa statistics ranged from 0.59 to 0.82 across the dietary components and Meal IQ.
A higher Meal IQ score was associated with a higher overall dietary quality including lower contents of fat, saturated fat and added sugars, higher contents of fiber, various vitamins and minerals, and more fruit, vegetables and fish.
Conclusion and perspectives
Offering a free school meal had a positive effect on the change in dietary quality of the lunches consumed by school children aged 7-13 years compared to packed lunches brought from home. No effect was measured when the school meals were no longer provided for free. The dietary effect of the school food programme did not depend on age.
The standardized DPM was shown to be valid and reliable for assessment of the dietary quality of packed lunches brought from home. Furthermore the Meal IQ was found to be valid and a useful evaluation tool for assessing the dietary quality of school meals or packed lunches brought from home.
Future research has to refine the methods for dietary assessment. Utilizing the technology for dietary assessment may decrease the burden of the researcher and thereby improve the cost-effectiveness and possibly the accuracy of the DPM. Using the DPM to estimate food intake in free-living conditions among children is also a relevant perspective because data on the entire diet could be achieved.
Furthermore, future research has to focus on development of multicomponent school-based interventions which take into account the multiple factors and environments which affect the dietary habits of children. The focus of such an intervention could be implementation of a sustainable school food programme. Another focus could be improvement of the packed lunches brought from home with the purpose to contribute to the shaping of a healthier dietary behaviour among Danish school children.
In 2007, the Danish Food Industry Agency announced a project where Danish schools could apply for funds to establish a school food programme to provide the school children with free school meals for two months during 2008. This school food programme should be tested and evaluated. The present PhD thesis is based on evaluation of the dietary effect of this project.
There is room for improvement of the dietary habits of Danish children. Dietary habits are influenced by multiple factors across different contexts. The school setting is known as a suitable arena for promotion of healthy eating. In Denmark most children eat a packed lunch brought from home.
It is challenging to collect dietary data from a pediatric population where recall problems exist and estimation of portion sizes can be complicated. Thus, to measure and assess the dietary effect of an intervention, new valid methods are needed.
The overall aim of this PhD thesis was to evaluate the dietary effect of a school food programme in Danish schools on the quality of lunch consumed by children aged 7-13 years compared to packed lunches brought from home. Furthermore, the aim was to develop appropriate methods to measure and assess dietary intake for evaluation of interventions, which are designed to promote credible evidence to this area. The objectives were; to evaluate the validity and reliability of a digital photographic method (DPM) to assess the quality of dietary intake from packed lunches brought from home among children aged 7-13 years (paper I); to develop and validate an index for assessment of dietary quality of school meals, either brought from home or provided by the schools (paper II); to evaluate the effect of implementing a school food programme on the dietary quality of lunches consumed by students aged 7-13 years compared to packed lunches brought from home and furthermore to investigate if a possible effect would differ between the youngest school children and the older (paper III).
Methods
The evaluation of the school food programme was conducted in 4 intervention schools and 4 control schools from all over Denmark. Data on packed lunches were collected at baseline. At 1st follow-up the children in the intervention schools were offered free school meals and at the 2nd follow-up the school meals were paid. The control group had packed lunches at all measurements. Collection of data covered 3 consecutive days during a week at each of the three measurements. In total 984 school children were invited at baseline – 493 from the 2nd -3rd grades and 491 from the 5th-6th grades. A standardized DPM was used to collect data on food intake 3 consecutive days in a week at all of the 3 measurements. To assess the dietary quality of food consumed a Meal Index of dietary Quality (Meal IQ) was developed.
The validity and reliability of the DPM was tested on weighed foods of 191 packed lunches. The Meal IQ was developed and validated against calculated nutrient content of both 191 packed lunches and 63 school meals.
Results
Implementing a school food programme increased the quality of dietary intake among school children aged 7-13 years at 1st follow-up where the school meals were free, compared to the packed lunches brought from home (P=0.004). At the 2nd follow-up, where the school meals were not provided for free, only a limited number of children ate school meals and there was no difference in quality of dietary intake at lunch among children in the intervention and control schools (P=0.343). The statistical analyses demonstrated some differences in changes in dietary quality intake at lunch between school children in the 2nd-3rd grades and 5th-6th grades. This was not due to different effect of the school food programme but was mainly explained by more skipped meals in the oldest age group compared to the youngest age group.
Correlation coefficients and cross-classifications between the DPM and the weighed foods showed good agreement. There were no statistical differences between fish, fat, starch, whole grains and Meal IQ using the two methods. Differences were found for fruit and vegetables. Bland-Altman analyses showed a tendency to underestimate high amounts of these variables using the DPM. For inter-rater reliability, Kappa statistics ranged from 0.59 to 0.82 across the dietary components and Meal IQ.
A higher Meal IQ score was associated with a higher overall dietary quality including lower contents of fat, saturated fat and added sugars, higher contents of fiber, various vitamins and minerals, and more fruit, vegetables and fish.
Conclusion and perspectives
Offering a free school meal had a positive effect on the change in dietary quality of the lunches consumed by school children aged 7-13 years compared to packed lunches brought from home. No effect was measured when the school meals were no longer provided for free. The dietary effect of the school food programme did not depend on age.
The standardized DPM was shown to be valid and reliable for assessment of the dietary quality of packed lunches brought from home. Furthermore the Meal IQ was found to be valid and a useful evaluation tool for assessing the dietary quality of school meals or packed lunches brought from home.
Future research has to refine the methods for dietary assessment. Utilizing the technology for dietary assessment may decrease the burden of the researcher and thereby improve the cost-effectiveness and possibly the accuracy of the DPM. Using the DPM to estimate food intake in free-living conditions among children is also a relevant perspective because data on the entire diet could be achieved.
Furthermore, future research has to focus on development of multicomponent school-based interventions which take into account the multiple factors and environments which affect the dietary habits of children. The focus of such an intervention could be implementation of a sustainable school food programme. Another focus could be improvement of the packed lunches brought from home with the purpose to contribute to the shaping of a healthier dietary behaviour among Danish school children.
| Original language | English |
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| Publisher | National Food Institute, Technical University of Denmark |
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| Publication status | Published - 2013 |