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Vitamin D Deficiency and Allergies During Pregnancy

9/10/2019 1:10:23 PM
vitamin dVitamin D is known to affect innate and acquired immunity. A study published in 2019 in PLoS One investigated the association between serum vitamin D deficiency and allergic symptoms. The study relied on data from a historical cohort of pregnant women enrolled in the Japan Environment and Children’s Study (JECS).
The JECS was initially designed to evaluate the effects of desert dust exposure on allergic symptoms in pregnant women in Japan. Questionnaires about allergic symptoms were completed by participants during the Asian dust seasons, on Asian dust days, and on randomly selected days throughout pregnancy. Serum samples were collected once each trimester. The current study measured 25(OH)D levels in the frozen serum samples and evaluated the association between vitamin D deficiency and allergic symptoms.

Study connects vitamin D levels and allergy severity in pregnant women

Vitamin D deficiency was defined according to the Institute of Medicine guidelines to be 25(OH)D < 20 ng/mL. Of the 1745 serum samples evaluated, 1233 (71%) showed vitamin D deficiency. When compared with non-deficient participants, pregnant women were 33% more likely to develop allergic symptoms when they were vitamin D deficient (adjusted odds ratio [OR] = 1.33; 95% CI, 1.07-1.64). As the vitamin D level increased, the odds of allergic symptoms decreased. Also, the risks associated with Asian dust events and pollen exposures were more evident in vitamin D deficient subjects than in vitamin D non-deficient subjects.

More specifics needed to pinpoint findings on vitamin D and pregnancy

The main strength of this study was the large dataset of a cohort that was considered to be a good representation of pregnant women in Japan. The limitations included the possibility of reverse causality (women with allergies might stay indoors and get less sun exposure), self-reporting of symptoms (rather than clinical confirmation), and an inability to generalize the findings from pregnant women to the broader population.
Nevertheless, the findings from this study could have far-reaching implications. The study concludes that it may be possible to reduce the symptoms of allergies by approximately 30% by ensuring a level of 20 ng/mL of serum 25(OH)D in pregnant women.
Kanatani KT, Adachi Y, Hamazaki K et al. Association between vitamin D deficiency and allergic symptom in pregnant women. PLoS One. 2019; 14: e0214797.