INMA: “New study links air pollution to lower vitamin D levels during pregnancy”

28/10/2024

A recent study, which analyzed data from multiple cohort studies across Europe and the United States, including the Spanish INMA project, has found that exposure to air pollution may lead to lower vitamin D levels in pregnant women. Specifically, the study highlighted the effects of fine particulate matter of less than 2.5 micrometers in diameter, known as PM_2.5.

Maintaining adequate vitamin D levels during pregnancy is crucial for both the mother and the developing baby. Insufficient vitamin D has been associated with pregnancy complications, as well as potential long-term impacts on a child’s health, affecting bone density, dental health, and cognitive development. Pregnant women can boost their vitamin D levels through sunlight exposure or by taking supplements.

Previous studies have suggested that air pollutants, such as PM_2.5, PM₁₀, or NO₂, could interfere with vitamin D production by blocking ultraviolet B (UVB) rays from reaching the skin or altering the body’s ability to metabolize the vitamin. While these mechanisms are suspected, it is still unclear at what level air pollution levels may significantly impact vitamin D levels in pregnant women.

Study details and findings

To explore this potential link, researchers gathered data from 15,935 pregnant women participating in five large cohort studies: the Amsterdam Born Children and their Development (ABCD) and Generation R studies based in the Netherlands, the Born in Bradford study based in England, the Project Viva study from the United States, and the INfancia y Medio Ambiente (INMA) study based in Spain. The study included women from four INMA regions: Asturias, Gipuzkoa, Sabadell, and Valencia.

Air pollution exposure was measured at the participants’ home addresses, with the main analyses focusing on nitrogen dioxide (NO₂) and PM_2.5. Vitamin D levels were analyzed from blood samples taken during early or mid-pregnancy. The researchers also considered various factors that could affect vitamin D levels, such as maternal age, ethnicity, and socioeconomic status.

The study revealed that higher exposure to PM_2.5 was linked to a greater likelihood of suboptimal vitamin D levels in pregnant women. This relationship was particularly strong in the cohorts from Bradford in England and Sabadell in Spain. Importantly, these findings emerged even at levels of air pollution much lower than those seen in previous studies from different regions, such as China.

The researchers noted differences in results between the cohorts and proposed that this could be due to variations in how air pollution was measured and the differences in composition of particulate matter in different regions. They also pointed out that previous studies had found links between larger particulate matter (PM₁₀) and vitamin D levels, but this study did not replicate those findings.

Future research and conclusion

The authors emphasized the need for further research to understand other factors that could influence the link between air pollution and vitamin D, such as time spent outdoors, skin pigmentation and supplement use. They also acknowledged a limitation in their study: while pollution exposure at home was measured, the study did not account for time women may have spent in other environments.

This study found a significant association between exposure to PM_2.5 and lower vitamin D levels in pregnant women. Given that vitamin D plays an essential role in the healthy development of children, the authors highlight the importance of reducing air pollution exposure as a potential public health priority for pregnant women.

Reference: Binter AC, Ghassabian A, Zou R, El Marroun H, Lertxundi A, Switkowski KM, Estarlich M, Rodríguez-Dehli AC, Esplugues A, Vrijkotte T, Sunyer J, Santa-Marina L, Fernández-Somoano A, Polanska K, McEachan RRC, Oken E, Tiemeier H, Guxens M. Associations of gestational exposure to air pollution with maternal vitamin D levels: a meta-analysis. J Clin Endocrinol Metab. 2024 Jun 13:dgae395. doi: 10.1210/clinem/dgae395. Epub ahead of print. PMID: 38870315.

Link to the scientific article: https://doi.org/10.1210/clinem/dgae395