Findings 12 058 of 12 231 represented live births, and
10 821 (91% of those alive) children were followed-up at age
1 year. Of the 10 366 children included in analyses, 81 were
diagnosed with diabetes during the study. Vitamin D
supplementation was associated with a decreased frequency
of type 1 diabetes when adjusted for neonatal,
anthropometric, and social characteristics (rate ratio [RR] for
regular vs no supplementation 0·12, 95% CI 0·03–0·51, and
irregular vs no supplementation 0·16, 0·04–0·74. Children
who regularly took the recommended dose of vitamin D
(2000 IU daily) had a RR of 0·22 (0·05–0·89) compared with
those who regularly received less than the recommended
amount. Children suspected of having rickets during the first
year of life had a RR of 3·0 (1·0–9·0) compared with those
without such a suspicion.