The study, conducted by authors from Spain, found that in 2,027 mother-child pairs, the prevalence of vitamin D3 deficiency was 17.5%, and around 40% of the children were overweight at the ages of 7 and 11 years.
The results showed that maternal vitamin D3 deficient status was associated with higher zBMI (the assessment for children’s BMI), higher fat mass percentage, higher odds of being overweight, and an increased risk of belonging to lower birth size followed by accelerated BMI gain trajectory in boys.
The study concludes: “Results support a sex-specific programming effect of early pregnancy vitamin D3 levels on offspring body composition into late childhood observed in boys.
“Prenatal vitamin D levels may be an early-modifiable risk factor to consider in order to prevent childhood overweight.”
Vitamin D deficiency
The high prevalence of vitamin D deficiency during pregnancy is a public health concern as it has been associated with poor health outcomes, including obesity in children.
Yet despite evidence linking low vitamin D levels to overweight or obesity risk in children, there is lacking evidence to support the causal role of prenatal vitamin D levels in the development of obesity.
Some studies have demonstrated the association between deficient vitamin D levels during pregnancy and adverse foetal outcomes, such as preterm birth or low birth weight, which have been associated with an increased susceptibility to develop diseases later in life, including cardiometabolic disease.
The authors of this new study note that several biologically plausible mechanisms support the association between vitamin D and infant growth and adiposity, namely the role of vitamin D on musculoskeletal health, as well as its role on lipolysis and adipogenesis. It is noted in the study, however, that the exact mechanisms are not well established yet.
However, previous meta-analysis revealed that vitamin D supplementation during pregnancy or early life was associated with lower BMI and zBMI from 3 to 6 years.
This new study aimed to investigate this association further, and found that low vitamin D levels during pregnancy were associated with higher body mass index, higher fat mass percentage, and increased odds of being overweight in boys, but not in girls.
2,027 mother–child pairs from the Spanish population-based birth cohort (INMA), were included in the study.
Vitamin D metabolic status was assessed by determining circulating plasma levels of 25-hydroxyvitamin D3 (25(OH)D3, via a blood sample drawn during pregnancy at an average of 12.9 weeks.
Sex and age-specific body mass index z-scores were calculated at 7 and 11 years, where overweight was defined as a z-score ≥ 85th percentile. Body fat mass was also measured at 11 years, identified using latent class growth analysis.
Results showed that children exposed to deficient vitamin D3 levels (<20 ng/mL) during pregnancy were more likely to have higher BMI z-score at age 7 and 11 years.
The authors note that all associations between pregnancy vitamin D3 levels and childhood body composition measures showed evidence specific to sex, explaining “as associations were all consistently stronger in boys than in girls, and most reached statistical significance in boys, whereas they were close to the null in girls.”
In boys, maternal vitamin D3 deficient status was associated with higher zBMI, higher fat mass percentage, higher odds of being overweight, and an increased risk of belonging to lower birth size followed by accelerated BMI gain trajectory.
The authors write: “A surprising finding in our study was that the effects of vitamin D deficiency were only present in boys.”
They hypothesise: “Though we do not have a clear explanation for the discrepancies regarding the sex differences of maternal vitamin D effect on body composition in the offspring, there is evidence from in vitro and animal studies that support a sex-specific metabolic response to maternal vitamin D deficiency during pregnancy.
“One explanation is that this relies on testosterone regulation of vitamin D metabolism in the placenta.”
Given the established link between estrogens and fat accumulation, the authors suggested that this finding may be one of the reasons for observing these sex-specific effects of vitamin D deficiency.
The authors note that the study did have some limitations, stating: “We cannot rule out the potential residual confounding on the associations due to factors that we have not been able to measure.
“For example, individuals might differ in their capacity to obtain 1,25(OH)2D, which is the biologically active form of vitamin D and highly regulated by calcium levels.
“Therefore, there will always be inter-individual variability that we cannot measure and may confound the associations.”
The authors recommend that future studies attempting to replicate the study could assess whether other factors, such as childhood diet or physical activity, have any influence on this association.
“Prenatal Vitamin D Levels Influence Growth and Body Composition until 11 Years in Boys”
Authors: Julia Sanguesa, Sandra Marquez, Mariona Bustamante, Jordi Sunyer, Carmen Iniguez, Jesus Vioque, Loreto Santa-Marina Rodriguez, Alba Jimeno-Romero, Matias Torrent, Maribel Casas and Martine Vrijheid.