Vitamin D supplementation in young children: associations with Theory of Planned Behaviour variables, descriptive norms, moral norms and habits.

OBJECTIVE: In the Netherlands, a supplementation of 10 mug vitamin D is recommended for children (aged 0-4 years), given that vitamin D contributes to the development of healthy bones and deficiency during childhood is a risk factor for osteoporosis at a later age. However, only 60 % of the Dutch children receive sufficient vitamin D supplementation a day. In order to develop interventions to improve supplementation intake, it is necessary to gain insight into the behaviour of parents in giving their children vitamin D supplementation and its association with variables of the Theory of Planned Behaviour, moral and descriptive norms and habits. DESIGN: A cross-sectional survey to assess present supplementation-related behaviour, knowledge, received information, intention, attitude, subjective norm, perceived behavioural control, moral norm, descriptive norm and habit. SETTING: Data obtained from a representative Internet Panel by means of electronic questionnaires. SUBJECTS: Parents (n 270) of children aged 0-4 years. RESULTS: Half of the parents (48.9 %) gave their child sufficient vitamin D supplementation. Giving the supplement at a fixed time, a positive intention and habit were significantly associated with actual behaviour. The higher age of the child, first-born status, a fixed time for taking vitamin supplementation, descriptive norm and moral obligation were significantly associated with intention. CONCLUSIONS: These results indicate that because many parents do not give their children adequate vitamin D supplementation, the promotion of supplementation during the first years of life is a necessity. Effective yet simple strategies should be developed, focused on improving moral obligation, descriptive norms and habit formation.