Regional differences in vitamin D levels and incidence of food-induced anaphylaxis in South Korea

Abstract Background Previous studies have suggested low vitamin D as a potential risk factor for food allergy/anaphylaxis. However, few studies have investigated the association between vitamin D and food-induced anaphylaxis (FIA) in South Korea. Objective To examine regional differences in serum vitamin D levels and FIA incidence. Methods We used nationwide data collected from 2011 to 2013. Data on vitamin D were obtained from the Korea National Health and Nutrition Examination Survey; data on FIA were obtained from the Health Insurance and Assessment Service. Districts were grouped into region 1 (lower solar radiation) and region 2 (higher solar radiation). We examined differences in FIA incidence and vitamin D levels between the regions, adjusting for age. Results The study included 2,814 patients with FIA and 15,367 people with available serum vitamin D measurements. Age-adjusted FIA incidence was 2.2 per 100,000 person-years in region 1 and 1.8 per 100,000 person-years in region 2 (relative risk, 1.23; 95% confidence interval, 1.09–1.39). Age-adjusted serum vitamin D levels were 16.5 ng/mL in region 1 and 17.8 ng/mL in region 2 (mean difference, 1.3 ng/mL; 95% confidence interval, 0.9–1.9). After stratification by age, sex, and area of residence, region 1 still had higher FIA incidence and lower vitamin D levels than region 2. Conclusion The present study found a higher incidence of FIA in regions with lower vitamin D levels in the population. Further investigation is necessary to identify any direct associations between vitamin D and food allergy/anaphylaxis.