This register-based national cohort study of 206,900 individuals investigated whether prenatal exposure to small extra doses of vitamin D from fortified margarine prevented inflammatory bowel disease (IBD) later in life; whether the risk of IBD varied according to month or season of birth; and finally, whether there was an interaction between exposure to extra D vitamin and month or season of birth. Fortification of margarine with vitamin D was mandatory in Denmark from the mid-1930s until 1st June 1985, when it was abolished. Two entire birth cohorts, each including two years, were defined: one exposed and one unexposed to the fortification policy for the entire gestation. All individuals were followed for 30 years from the day of birth for an IBD diagnosis in Danish hospital registers. Logistic regression analyses were used to estimate odds ratios (OR) and 95% confidence intervals (CI). Odds for IBD was lower among those exposed to extra D vitamin compared to those unexposed, OR = 0.87 (95% CI: 0.79; 0.95). No association with month or season of birth was found. However, estimates suggested that particularly children born during autumn may have benefitted from the effect of small extra doses of vitamin D. This is, to our knowledge, the first study to explore if prenatal exposure to vitamin D from fortification influenced the risk of IBD. Our results suggest that prenatal exposure to small amounts of extra vitamin D from food fortification may protect against the development of IBD before 30 years of age.

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.

Few studies have examined the role of maternal diet in relation to development of coeliac disease (CD). In Denmark, cancellation of mandatory vitamin D fortification of margarine in June 1985 provided this opportunity. This study examined if season of birth or prenatal exposure to extra vitamin D from food fortification were associated with developing CD later in life. A strength of this study is the distinctly longer follow-up of patients (30 years). This register-based study has a semi-ecological design. Logistic regression analysis was used to estimate odds ratios and to calculate 95% confidence intervals. The odds ratio for developing CD was 0.81 (95% CI 0.66; 1.00 p = 0.054), comparing those with fetal exposure to mandatory vitamin D fortification policy of margarine to those without after adjusting for gender and season of birth. There was a statistically significant season effect particularly for children born in autumn (OR 1.6 95% CI 1.16; 2.21) and born in summer (OR 1.5 95% CI 1.1; 2.1) when compared to children born in winter. Although this study did not find evidence to support the premise that prenatal exposure to small extra amounts of vitamin D from a mandatory food fortification policy lowered risk of developing CD, the small number of CD cases and observed association between season of birth and CD suggest that environmental exposure ought to be further explored.

Understanding families' food purchase decision-making is essential to developing successful interventions to promote healthier behaviours. Several factors can influence the foods people purchase. However, knowledge about how parents handle dilemmas in food purchase decisions and how these decisions affect families' food purchases is scarce. This study explores families' food purchase decisions in supermarkets and illustrates how parents navigate the tension between their values and contextual and situational circumstances (e.g. family situation). We conducted 37 semi-structured, shop-along, and photo-elicited interviews with parents from fifteen families with children ranging from 0 to 19 years of age (September 2022-January 2023). We used an abductive analytical approach to investigate the role of conscience and morality in our empirical findings. We applied the theoretical concept of moral labour to examine how individuals navigate the discomfort associated with guilt or a guilty conscience, which arises from conflicts or dissonance of their values when making food purchases in supermarkets. Food purchase decisions were influenced by moral considerations related to animal welfare, climate, parental responsibility, and good and healthy food. However, product availability and presentation, price, and the parent-child interaction, as well as contextual and situational circumstances, could challenge parents' values, triggering moral labour. The study illustrates how parents performed moral labour, e.g., minimising the health impact, to reconcile with negative feelings of conflicting values. Future intervention studies should consider focusing on supportive food environments over individual behaviour changes to minimise the potential moral labour among parents from such initiatives.

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.

Partnerships between researchers and food retailers are advocated as necessary for developing sustainable and effective health-promotion initiatives in supermarkets. However, little is known about how such partnerships evolve and influence different phases of intervention research. This study explores how partnerships between researchers and food retailers develop during the pre-intervention phase and examines the factors that influence both the partnerships and the initiatives they produce. The empirical case used in the study is a partnership between intervention researchers, food retailers, and public health advocates that aimed to develop and test healthy food retail initiatives to make healthy food choices easy for customers. We conducted an ethnographic study covering the pre-intervention phase from the establishment of the partnership in 2019 to the feasibility test of the initiatives in 2021. We used participant observation of meetings and intervention development activities, qualitative interviews with partners, and document analysis of email correspondence and project materials. We analysed the data abductively, drawing on a narrative analytical approach and theoretical concepts of institutional logics and negotiation. We present a narrative in six chapters illustrating how market logic dominated the selection and development of healthy food retail initiatives, ultimately compromising the researchers’ original research interests. Furthermore, the pre-intervention phase was challenged by an unclear division of roles and responsibilities, misaligned expectations, high staff turnover in the retail organisation, and the Covid-19 pandemic. These challenges resulted in growing mistrust and an asymmetric partnership that undermined the progress and potential of the project. Using the lens of institutional logics, we show how differing interests and perspectives between partners – for example regarding health and consumer behaviour – can make it difficult to realize the original research ideas and build a trusting relationship. Overall, this study illustrates the complexity of research partnerships with commercial actors such as food retailers. To develop and implement effective health-promotion initiatives in a food retail setting, researchers must stay mindful of their initial research interest, integrity, and study design, ensuring they are not compromised in the collaboration.