Purpose: From September 2010 until November 2019, Ireland's infant vitamin D supplementation policy recommended administration of 5 μg/day of vitamin D3 from birth to 12 months to all infants, regardless of feeding method. This study aims to examine policy adherence.
Methods: In the prospective COMBINE birth cohort study (recruited 2015-2017), detailed longitudinal supplement data were examined in 364 infants across the first year of life, according to product type, dose, frequency, and duration. Vitamin D supplement use at 2, 6, and 12 months in COMBINE was compared with the BASELINE cohort (recruited 2008-2011, n = 1949).
Results: In COMBINE, 92% of infants initiated supplementation at birth. The median supplementation duration was 51 (40, 52) weeks, with a range of 3-52 weeks. While supplementing, most parents (92%) used an exclusive vitamin D supplement as recommended and 88% gave 5 µg/day. Half (51%) gave vitamin D daily and a further 33% supplemented at least 3-6 times/week. Overall, 30% adhered fully to the policy, providing 5 µg vitamin D3 daily from birth to 12 months. A further 16% were broadly compliant, giving 5 µg frequently for the full 12 months. Vitamin D supplement use at 2, 6, and 12 months in COMBINE was 93%, 89%, and 72%, considerably higher than our earlier BASELINE cohort at 49%, 64%, and 44% at the same time points (all P < 0.001).
Conclusions: We report a high level of vitamin D supplementation initiation at birth, with full to broad policy adherence among more than half of infants. There is scope to improve overall compliance by focusing on supplementation frequency.
Keywords: Adherence; Birth cohort; Infancy; Policy; Supplementation; Vitamin D.