A recent study found that urban environments have significantly increased rates of vitamin D deficiency and asthma compared to rural environments.

In past studies, urban city centers have been linked to a higher prevalence of vitamin D deficiency and asthma.  People spend more time indoors and have less opportunity to get outside for adequate sun exposure in populous, urban areas. Higher rates of asthma in cities are thought to be caused by the high level of pollutants and toxins in the air. Furthermore, previous research suggests that vitamin D deficiency may increase the risk for asthma.

In the current study, researchers at John Hopkins University studied a cohort of children ages 13-15 that lived in Peru. Of the 1,441 children they studied, 706 of them were from Lima,  and 735 of them were from Tumbes. Both towns are close to the equator and have abundant sunlight, but they have different levels of urbanization. Lima, the capital of Peru, is a heavily populated, urban city, whereas Tumbes is a rural town.

The researchers wanted to see if vitamin D deficiency and asthma are more common in urban areas than in rural ones.

The researchers found that rates of both vitamin D deficiency and asthma among children were highest in the urban city of Lima compared to the rural town of Tumbes. They found that 47% of children were deficient in vitamin D and 12% had asthma in Lima, compared to 7% of the children who were vitamin D deficient and 3% who had asthma in Tumbes.

“In summary, vitamin D levels were low in an urban versus rural setting in two equatorial populations and our findings highlight the importance of an urban lifestyle as a risk factor for vitamin D deficiency. Asthma prevalence was greatest in the study population with a higher prevalence of vitamin D deficiency, suggesting an ecological relationship between vitamin D and asthma,” the researchers concluded.

Source

Checkley, et al. 25-hyrdoxy vitamin D levels are associated with childhood asthma in a population-based study in Peru. Journal of the British Society for Allergy and Clinical Immunology, 2014.