Effect of the multicomponent healthy high school intervention on meal frequency and eating habits among high school students in Denmark: a cluster randomized controlled trial

Background

Previous studies have shown that multicomponent interventions may improve meal frequency and eating habits in children, but evidence among young people is limited. This study evaluated the effect of the Healthy High School (HHS) intervention on daily intake of breakfast, lunch, water, fruit, and vegetables at 9-month follow-up.

Methods

The study included first-year students (≈16 years) attending high school in Denmark. Participating schools were randomized into the HHS intervention (N = 15) or control group (operating as usual) (N = 15). The intervention was designed to promote well-being (primary outcome) by focusing on healthy habits including meals, stress prevention, and strong peer relations. It included a curriculum, structural and organisational initiatives, a workshop, and a smartphone application. Students completed self-administered online questionnaires at the beginning of the school year and nine months later. To account for clustering of data, we used multilevel logistic regression analyses to estimate odds ratios (OR). We applied an intention-to-treat approach with multiple imputations of missing data.

Results

At baseline 4577 of 5201 students answered the questionnaire and 4512 at follow-up. In both groups the proportion of students eating breakfast decreased from approximately 50% to 40% from baseline to follow-up, and lunch frequency decreased from approximately 50% to 47%. Daily water intake, intake of fresh fruit and intake of vegetables remained unchanged from baseline to follow-up. There were no significant between group differences on any of the outcomes at first follow-up: breakfast: OR = 0.85 (95% CI: 0.65;1.10), lunch: OR = 0.96 (95% CI: 0.75;1.22), water intake: OR = 1.14 (95% CI: 0.92;1.40), intake of fresh fruit: (OR = 1.07, 95% CI: 0.84;1.37), vegetables: (OR = 1.01, 95% CI: 0.77;1.33).

Conclusion

No evidence of an effect of the HHS intervention was found for any of the outcomes. Future studies are warranted to explore how health promoting interventions can be integrated in further education to support educational goals. Moreover, how to fit interventions to the lives and wishes of young people, by also including systems outside of the school setting.

Trial registration

ISRCTN, ISRCTN43284296. Registered 28 April 2017 - retrospectively registered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12966-021-01228-2.

Adaptation, Student Participation and Gradual Withdrawal by Researchers as Sustainability Strategies in the High School-Based Young and Active Intervention: School Coordinators' Perspectives

Ensuring the sustainability of school-based public health intervention activities remains a challenge. The Young and Active (Y&A) intervention used peer-led workshops to promote movement and strengthen students' sense of community in 16 Danish high schools. Peer mentors inspired first-year students to implement movement activities. To support sustainability, we applied a three-year stepwise implementation strategy using university students as peer mentors in year 1 and senior high school students in the following two years. This study explores the sustainability potential of Y&A, focusing on school coordinators' reflections on the intervention's fit to their schools and the student-driven approach, and we assess the three-step implementation strategy. The study is based on telephone interviews with coordinators (n = 7) from schools that participated in all three years and participant observations of four workshops (a total of approximately 250 participating students). Results were generated through an abductive analysis. Seven schools continued the intervention throughout the three years and adapted it to fit their priorities. The student-driven approach was perceived to be valuable, but few student-driven activities were initiated. Teacher support seemed crucial to support students in starting up activities and acting as peer mentors in workshops. The three-step implementation strategy proved valuable due to the peer-approach and the possibility of gradual adaptation. In future similar initiatives, it is important to address how the adequate staff support of students can be facilitated.

Assessing Health Consequences of Vitamin D Fortification Utilizing a Societal Experiment Design: Methodological Lessons Learned from the D-Tect Project

By utilizing historical changes in Danish legislation related to mandatory vitamin D fortification of margarine, which was implemented in the mid 1930s and abruptly abandoned in June 1985, the studies in the D-tect project investigated the effects of vitamin D on health outcomes in individuals, who during gestation were exposed or unexposed to extra vitamin D from fortified margarine. This paper reviews and narratively summarizes the analytic approaches alongside the results of the societal fortification experiment studies from the D-tect project and addresses the challenges in designing societal experiment studies and evaluating their results. The latter are discussed as lessons learned that may be useful for designers of similar studies, expected to be extensively utilized while researching the health consequences of the COVID-19 pandemic by comparing individuals born before and after the epidemic. In the D-tect project, 16 articles based on the societal fortification experiment were published analyzing 10 different outcomes and using different statistical approaches. Lessons learned included the detail of the analysis of the historical information on the exposure, availability and validity of the outcome data, variety of analytical approaches, and specifics concerning vitamin D effect evaluation, such as consideration of the influence of sunshine or season. In conclusion, the D-tect project clearly demonstrated the cost-effectiveness and research potential of natural- or societal-experiment-based studies.

Prenatal exposure to extra vitamin D from fortification and risk of developing coeliac disease

Introduction

Few studies have examined the role of maternal diet in relation to development of autoimmune diseases such as coeliac disease (CD). In Denmark, cancellation of mandatory vitamin D fortification of margarine in June 1985 provides this opportunity. This study examined if prenatal exposure to extra vitamin D from food fortification or season of birth were associated with a decreased risk of developing CD later in life. If low prenatal vitamin D levels are a risk factor, there are immediate, cheap and easy public health implications.

Methods

This register based study has a partially ecologic design. The two entire cohorts were created using information available from the Danish birth registry and development of CD (ICD-8 269 ICD-10 K90) over 30 years was retrieved from the Danish National Patient Register. Logistic regression analysis was used to generate odds ratios and 95% confidence intervals.

Results

There was a lower odds ratio of developing CD (OR: 0.811 95% CI 0.655; 1.003) from the exposed birth cohort adjusting for sex and season of birth. There was a significant season effect particularly for children born in autumn (OR 1.6 95% CI 1.16; 2.21) and born summer (OR 1.5 95% CI 1.1;2.1) when compared to children born in winter.

Conclusions

The results indicate a potential protective effect of a small extra intake of vitamin D from food fortification by pregnant women in relation to the risk of their offspring developing CD. This conclusion is further supported by the results showing that summer born children, where first half of gestation occurred during the dark winter season, had a higher risk of CD. This research lends support for the reconsideration of vitamin-D food fortification in Denmark.

Key messages

Exposure to even a small amount of vitamin D prenatally may protect against developing coeliac disease later in life. Association between season and CD indicates that vitamin D may play an important role in relation to fetal programming.

Prenatal exposure of extra vitamin D from fortification and later risk of inflammatory bowel disease

Introduction

Inflammatory bowel disease (IBD) is a chronic immune-mediated inflammatory disease that can affect the entire digestive tract. Approximately 1% of the Danish population has IBD today. Both the incidence and prevalence of IBD are increasing globally, but the etiology of IBD is still not fully understood. Some, but not all studies find that vitamin D has both protective and therapeutic effects on IBD. To our knowledge, no other study has investigated prenatal exposure to extra vitamin D from either fortified food, diet or supplements in relation to IBD. The aim of this study was to investigate whether a small extra dose of vitamin D from fortification during gestation, was associated with a lower risk of developing IBD in the offspring.

Methods

In 1985 mandatory fortification of margarine with vitamin D in Denmark was canceled. To investigate the effect of this policy change we selected all individuals from 2 full year birth cohorts before and after the termination of the mandatory fortification. All individuals were followed for 30 years. By merging data from the Medical Birth Registry with the Danish National Patient Registry, we identified individuals with IBD.

Results

217,249 individuals were included in the analysis. 875 among the exposed and 1102 among the unexposed fulfilled the criteria for being diagnosed with IBD. A lower odds ratio OR = 0.867 (95% CI: 0.792;0.947) for IBD was observed among those who had been exposed to extra vitamin D from fortified margarine during gestation, compared to those who had not been exposed. The analysis was adjusted for sex and season of birth, but results were essentially similar before and after this adjustment.

Conclusions

This study shows, that a small extra dose of vitamin D from fortified margarine during gestation may lower the risk of developing IBD in the offspring, until the age of 30. If these results can be replicated, fortification with vitamin D could be recommended to prevent IBD on a public level.

Key messages

Prenatal exposure of vitamin D from fortified food could lower the risk of IBD later in life. Fortification with vitamin D even at a relatively low level could have public health benefits.