Worsening air pollution an unfamiliar cause of low vitamin D levels: A systematic literature review

Abstract

Air pollution is widely recognized as a future biohazard, yet its direct effects on human health, particularly in relation to bone health and vitamin D levels, are inadequately understood. While the detrimental impact on respiratory and cardiovascular health is well-documented, the correlation with vitamin D deficiency remains weak.
To explore the relationship between air pollution and vitamin D levels, an extensive search of scientific literature was conducted. This comprehensive search encompassed databases such as PubMed, Cochrane Library, and DOAJ, while also examining the bibliographies of relevant articles. The inclusion criteria focused on studies that specifically investigated the association between air pollution and vitamin D levels, while excluding systematic reviews, case reports, editor's letters, and studies lacking pertinent explanations or causative factors. Each included study underwent rigorous evaluation of its methodological quality, with data extraction performed to assess the reliability and robustness of the evidence for each research question.
The majority of studies have consistently demonstrated a negative correlation between ambient air pollution and vitamin D levels in humans. Several mechanisms have been proposed to explain this relationship, including reduced exposure to sunlight due to increased air pollution, production of reactive oxygen particles, and inflammation leading to decreased vitamin D synthesis. Moreover, certain pollutants, such as particulate matter and nitrogen dioxide, have been found to have a more pronounced impact on vitamin D levels. Variables such as age, gender, season, and geographical location may also influence the association between air pollution and vitamin D levels. Lifestyle factors, including indoor confinement and pre-existing vitamin D deficiency, may exacerbate the detrimental effects of air pollution.
In conclusion, air pollution detrimentally affects vitamin D levels primarily through increased body inflammation and the generation of free radicals. The presence of elevated levels of particulate matter and nitrogen dioxide further compounds this effect. Additionally, decreased cutaneous production of activated vitamin D, resulting from reduced ultraviolet B radiation penetration due to decreased Air Quality Index, contributes to the negative impact. Studies suggest that the intake of exogenous vitamin D supplements and adherence to a calcium-rich diet may confer benefits to individuals residing in highly polluted areas. To address this issue, public health policies should emphasize outdoor exposure to sunlight, promote healthy dietary choices, and reduce overall exposure to pollutants.