Study Uncovers Environmental Risk Factors that Influence Vitamin D Deficiency in Pregnant Women

A scientific team led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, has studied the determinants that influence vitamin D levels in pregnant women. After analysing more than 100 environmental, behavioural and socio-demographic factors, they found that younger women with a higher body mass index and who live in areas with more pollution and lower levels of humidity and ultraviolet radiation are at greater risk of vitamin D insufficiency.

Vitamin D deficiency has been linked to cancer, cardiovascular and autoimmune diseases, diabetes and adverse birth and delivery outcomes, such as pre-eclampsia or gestational diabetes. During pregnancy, the mother is the only source of vitamin D for the foetus, so a lack of vitamin D has been associated with later consequences, such as childhood asthma, skeletal abnormalities and impaired neurodevelopment .

The study included data from more than 2,000 women participating in the cohorts of Gipuzkoa, Sabadell and Valencia (Spain) of the INMA Project . Fifty-one percent of the participants showed vitamin D levels below the Endocrine Society recommendation (30 ng/mL). This is a higher percentage than in other European countries, such as the Netherlands, where in another study the percentage of women with vitamin D insufficiency was 33%.

The aim of the research was to assess the determinants of vitamin D levels during pregnancy by analysing more than 100 socio-demographic, lifestyle or environmental factors . To determine the level of vitamin D in the plasma of the participants, a blood sample was taken and, together with a urine sample, was also used to measure the presence of endocrine disruptors and other chemical pollutants. Socio-demographic (age, education, socio-economic status, etc.) and lifestyle data (diet, work exposure, physical activity) were obtained through questionnaires. Parameters of different environmental determinants, such as air pollution, temperature and humidity, ultraviolet radiation and exposure to green spaces, were obtained from the address of residence.

More vitamin D at older ages

Statistical analysis revealed that older pregnant women had higher vitamin D levels than younger women, which the team attributed to the likelihood that older women are more aware of the risks and adopt healthier lifestyles, in line with previous hypotheses by other authors.

Similarly, women with higher socioeconomic status also had higher levels of the vitamin, which may be attributed to factors such as a higher quality diet or more outdoor physical activity.

Regarding the association between higher body mass index and lower vitamin D levels , the research team's hypothesis, in line with the assumptions of other authors, is that more adipose tissue may cause the vitamin to be stored there, lowering the levels of available vitamin.

Sun and vitamin D

Most vitamin D is synthesised through the endogenous process of photosynthesis, which explains why UV exposure was associated with higher levels of vitamin D in the participants. In addition, women residing in more humid regions were also found to have higher levels of vitamin D, suggesting greater exposure to sunlight.

A similar mechanism may explain other associations found. Participants who were more exposed to air pollution had lower vitamin D levels. According to the team's hypothesis, air pollutants such as particulate matter can absorb and diffuse ultraviolet photons, thus impairing the internal production of the vitamin.

"Our results highlight the influence of socio-demographic, environmental and lifestyle-related factors on vitamin D levels in pregnant women", says Maria Llopis, ISGlobal researcher and first author of the study.

Role of vitamin D supplementation

Analyses of this study indicate that supplementation improves maternal vitamin D levels. However, Paula Sol Ventura, a paediatrician on the research team, stresses: "Excess vitamin D can be toxic to the mother and foetus. Its generalised supplementation is not recommended and should only be done under medical supervision".

Predictive techniques using machine learning

The research included a machine learning component, by which data from participants was used to try to predict vitamin D insufficiency before it occurs. "This study shows the potential of machine learning techniques for screening women at risk of vitamin D insufficiency, suggesting that it could be a relevant tool for public health policy", concludes Paula Petrone, ISGlobal researcher and one of the senior authors of the study. In this analysis, ambient humidity and the concentration of PM2.5 particles in the air emerged as two of the most relevant determinants of vitamin D levels.

Reference

Llopis M, Ventura PS, Brachowicz N, Sangüesa J, Murcia M, Lopez-Espinosa MJ, García-Baquero G, Lertxundi A, Vrijheid M, Casas M, Petrone P. Sociodemographic, lifestyle, and environmental determinants of vitamin D levels in pregnant women in Spain. Environ Int. 2023 Dec;182:108293. doi: 10.1016/j.envint.2023.108293 . Epub 2023 Nov 4. PMID: 37984291.