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 microg 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.