Complex relationships between vitamin D and allergic sensitization among Puerto Rican 2-year-old children

Vitamin D, skin filaggrin, allergic sensitization, and race

BACKGROUND

In addition to its involvement in both the innate and adaptive immune systems, vitamin D has been found to affect keratinocyte function and proliferation, suggesting a possible role for vitamin D in cutaneous allergic sensitization.

OBJECTIVE

To explore the role of circulating vitamin D levels in allergic sensitization.

METHODS

Serum 25-hydroxyvitamin D (25(OH)D) levels were measured in a subset of children (N = 323) enrolled in the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children cohort, a prospective early life cohort of children with atopic dermatitis. Allergic sensitization was determined using skin prick testing, and FLG expression in the keratinocytes was measured by quantitative polymerase chain reaction. Multiple Poisson regression was used to evaluate interaction effects between serum 25(OH)D levels and FLG expression with sensitization load as the outcome.

RESULTS

Black participants had significantly lower mean levels of serum 25(OH)D compared with non-Black participants (29.3 vs 32.9 ng/mL; P < .001). FLG expression and sensitization load were negatively correlated in non-Black participants with 25(OH)D levels less than 27.2 ng/mL (Rho = -0.45; P = .02). No association between FLG expression and sensitization load was found in Black participants or participants with 25(OH)D levels greater than or equal to 27.2 ng/mL. Multiple Poisson regression models confirmed that 25(OH)D levels interact with FLG expression to affect sensitization load in non-Black participants.

CONCLUSION

Despite lower vitamin D levels in Black participants, sensitization load was associated with nonlesional skin FLG expression in non-Black, but not Black, children with low vitamin D levels. Thus, a complex interplay of factors determines the impact of vitamin D on allergic sensitization.

Vitamin D and iron status in children with food allergy

BACKGROUND

Children with food allergy are at specific risk for nutritional deficiencies.

OBJECTIVE

To retrospectively determine prevalence of vitamin D and iron deficiencies in children with or without food allergy (FA).

METHODS

We compared the markers of vitamin D and iron status of 0 to 17-year-olds with cow's milk allergy (CMA) (n = 77), those with other FAs (n = 70), and those with atopy without FA (n = 87) at an academic pediatric allergy practice. Multiple linear regression analyses were performed to determine the impact of CMA and other FAs on vitamin D levels and iron markers.

RESULTS

Vitamin D deficiency was detected in one-fourth and insufficiency in one-third of children with CMA and other FAs and in those with atopic diseases but no FA, respectively. Vitamin D levels were associated with vitamin D supplementation and consumption of breast milk, cow's milk, infant formula, or plant-based milk beverage, but not with CMA or other FAs. Older children with FA who did not consume any cow's milk or alternative milk beverage were at highest risk for vitamin D insufficiency. Children with CMA have a higher rate of iron deficiency anemia (8%) than children with other FAs (1%) or those with no FA (5%, P < .001); however, suboptimal levels of transferrin saturation and iron were detected in up to one-third of children with CMA or other FAs.

CONCLUSION

Vitamin D deficiency and insufficiency is common in children with atopy overall, but children with CMA are at higher risk for iron deficiency anemia. Intensive nutritional counseling and nutrient intake monitoring, specifically for vitamin D and iron in those avoiding cow's milk, are necessary to optimize nutritional status.

Associations between serum 25-hydroxyvitamin D levels and allergic sensitization in early childhood

BACKGROUND AND OBJECTIVES

Vitamin D status may be related to allergen sensitizations, but the evidence is inconsistent. The objective of this study was to assess whether serum 25-hydroxyvitamin D (25(OH)D) levels were associated with allergic sensitizations in early childhood.

METHODS

Data were collected from 2642 children who visited the Guangdong Women and Children's Hospital from January 2016 to May 2017 for routine health check-ups. Serum 25(OH)D levels were tested by electrochemiluminescence immunoassay. Allergic sensitizations including food and inhalant allergens were tested for specific IgE antibodies at one year (12 months 0 days through 12 months 30 days) and two years (24 months 0 days through 24 months 30 days) of age.

RESULTS

The mean level of serum 25(OH)D was 86.47±27.55nmol/L, with a high prevalence of vitamin D insufficiency (<75nmol/L) in children aged 0-2 years (36.8%). Lower 25(OH)D levels with serum total IgE of more than 200IU/mL (81.54±25.53nmol/L) compared with less than 100IU/mL (87.92±28.05nmol/L). The common sensitization to allergens in children aged one and two years were milk (44.2%), cat epithelium (26.4%), egg (13.1%), dog epithelium (12.7%) and Dermatophagoides farinae (6.7%). After multivariate adjustment, data in 25(OH)D treated as a continuous variable or categories, no consistent associations were found between 25(OH)D levels and allergen-specific IgEs.

CONCLUSIONS

Serum 25(OH)D level showed an inverse relationship with total IgE level in early childhood. However, there is lack of evidence to support associations between low 25(OH)D levels and allergic sensitization to various allergens.