High dose vitamin D supplements given to breastfeeding women may be a way to improve babies’ vitamin D status according to new research from the University of Otago in New Zealand.
The randomised controlled trial of 90 pregnant women (mean age 32.1 years) who indicated an intention to breast feed for six months (71 percent exclusively breastfeeding at week 20) were randomly assigned to receive either cholecalciferol (50,000 or 100,000 IU) or placebo monthly from week four to week 20 postpartum.
Vitamin D is essential for calcium and bone metabolism and is mainly obtained from exposure to sunlight, with low levels being found in food and breast milk. Risk factors for infant vitamin D deficiency – which can lead to rickets – include adhering to recommendations to avoid direct sunlight exposure in the first 6 months of life, and being exclusively breastfed.
According to study co-author Dr Ben Wheeler, despite recommendations for daily vitamin D supplementation for babies during breastfeeding, compliance is low.
“We wanted to investigate that if mothers take a monthly high-dose supplement this could offer another way to help infants receive sufficient levels of the vitamin,” Dr Wheeler said.
Changes to serum cholecalciferol (25(OH)D) from baseline to week 20 in both mothers and babies were estimated using a linear fixed-effects regression model with adjustments for confounders of season of birth, vitamin D-fortified formula intake and infant and maternal skin colour.
After week 16, changes in the maternal serum levels of 25(OH)D were significantly higher in the 50,000-IU and 100,000-IU groups (12.8nmol/L; 95% CI 0.4,25.2nmol/L and 21.5nmol/L; 95% CI: 9.2, 33.8nmol/L, respectively) than in the placebo group (P=0.43 and P< 0.001).
Unadjusted mean changes in infants’ serum 25(OH)D were not different to that of placebo, however after adjustments for confounders, the mean change effect size for the 100,000-IU/mo group was 19.1nmol/L (95% CI: 2.5, 35.6 nmol/L; P=0.025) higher than that in the placebo group.
These results indicate that maternal cholecalciferol supplementation at a dose of 100,000 IU/month during the first five months of breastfeeding potentially benefits infant vitamin D status.
"At this dose, the improvement in vitamin D status appears to offer some protection against moderate to severe deficiency in infants, as only one of the babies in the 100,000-IU group showed serious deficiency compared to six in the placebo group," Dr Wheeler says.
Dr Wheeler adds that there is growing concern internationally that the number of children suffering from vitamin D deficiency is increasing. "If further research confirms our study's findings then the next step would be to investigate how the monthly supplementation compares in effectiveness to mothers taking daily or weekly vitamin D doses," he says.
*NB: the doses used in this study are considered extremely high, and no pregnant or breastfeeding woman should supplement with high dose vitamin D unless they are under the supervision of their doctor.
J Nutr 146 (8), August 2016. doi: 10.3945/jn.116.236679.