A recent follow-up study of the MAVIDOS trial confirmed that vitamin D supplementation during pregnancy improves bone mineral density in children, with benefits lasting up to age 7.
Study: Vitamin D supplementation during pregnancy and bone mineral density in children. Follow-up of a randomized controlled trial. Image credit: April stock / Shutterstock.com
Previously, the MAVIDOS trial reported that vitamin D supplementation during pregnancy significantly improved children’s bone mineral density (BMD) measured at age 4. In a recent study published in the American Journal of Clinical Nutrition, researchers looked at whether this BMD improvement persisted beyond early childhood.
What is the MAVIDOS Study?
The MAVIDOS study was a randomized controlled trial (RCT) evaluating the effects of vitamin D supplementation during pregnancy in the UK. All participants enrolled in the study were between 11 and 14 weeks pregnant and received 1,000 IU of vitamin D per day until birth.
A total of 965 children were included in the study, of which 723 were born at term. Of these term children, 477 underwent dual-energy X-ray absorptiometry (DXA) scans to assess BMD at age 4 years. By the second time point, between 6 and 7 years of age, 447 children had a second DXA scan.
Children who completed the second visit were more likely to be born to older mothers who did not smoke and had higher levels of education. These children were also breastfed for a longer period, and there was a small increase in the proportion of children taking vitamin D supplements since the initial assessment visit.
Improve bones
BMD and bone mineral density (BMAD) were measured using whole-body except head (WBLH) DXA scans. At age 6-7 years, WBLH BMD and BMAD were higher in the vitamin D group than in the placebo group.
Children whose mothers received vitamin D supplementation during pregnancy had higher WBLH BMD and BMAD measures, even after controlling for sex, height, weight, duration of breastfeeding, and vitamin D supplementation at age 6–7 years.
In some children who underwent DXA scans at birth and both assessment time points, we observed a similar increase in WBLH bone results at both time points.A trend towards increased lumbar spine BMAD at 6–7 years of age was also observed.
The primary aim of the MAVIDOS study was to test for improvements in BMC at birth, but no difference was found with supplementation. However, infants born in the winter months had higher bone mineral content (BMC) than placebo.
How do these findings compare to other studies?
This finding is consistent with the findings of the Copenhagen Childhood Asthma Prospective Study (COPSAC2010). However, the Bangladesh study did not show such improvements. Baseline health conditions such as malnutrition and infections may contribute to these conflicting results, but further research is needed to clarify these differences.
An observational study from Australia also showed similar benefits in offspring at age 20 years when mothers were given vitamin D supplementation at 18 weeks.
How does maternal vitamin D supplementation support bone density in children?
Vitamin D supplementation during pregnancy does not increase calcium availability to the developing fetus, even though it may increase fetal vitamin D levels and enhance calcium absorption during the first few months of life. Increased anti-rickets activity in breast milk may also increase bone mineralization in the child.
Epigenetic mechanisms may also be involved in the effects of vitamin D supplementation on bone later in childhood rather than at birth. For example, vitamin D may stimulate bone’s response to mechanical loading when children begin to move independently. Alternatively, higher vitamin D levels in early infancy may promote spinal growth during a period of rapid spinal growth and improve bone mineralization earlier than in later childhood.
Conclusion
The findings reaffirm that the positive effects associated with vitamin D supplementation during pregnancy persist beyond age 4 and into late childhood, but validation and extension of these findings is required before vitamin D supplementation during pregnancy can be recommended at 1,000 IU per day.
The increases in BMD observed during childhood are expected to reduce fracture risk, as confirmed by one retrospective analysis of a Danish trial. Future studies are needed to determine whether these increases in BMC and BMD persist as children transition into adulthood. These effects are clinically important in reducing fracture risk due to bone fragility.
Journal References:
Moon, RJ, D’Angelo, S., Curtis, EM, et al. (2024). Vitamin D supplementation during pregnancy and bone mineral density in children: A follow-up study of a randomized controlled trial. American Journal of Clinical Nutrition. doi:10.1016/j.ajcnut.2024.09.014.
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