Vitamin D supplementation may reduce respiratory infections in children

Researchers in Romania investigated the supplement habits in 194 participants, finding that vitamin D shows protective effects across all age groups, but is particularly notable in children under 6 years old.

They wrote in the journal Nutrients ​that ​“These findings support the importance of maintaining adequate vitamin D status in the pediatric population as a potential strategy to prevent respiratory infections.”

They noted that given the high prevalence of vitamin D deficiency, especially in areas with limited sunlight, understanding its role in respiratory infections is critical for public health.

Vitamin D and respiratory health​

Vitamin D, produced in the skin through UVB exposure​ and obtained from foods like fatty fish and fortified products, regulates calcium balance and bone metabolism. In addition to its role in bone health, vitamin D has immunomodulatory effects​, affecting innate and adaptive immune responses.

Respiratory infections are a major cause of illness​ and death among children and adolescents, who are especially vulnerable due to developing immune systems and frequent exposure to pathogens.

Several studies​ suggest that higher vitamin D levels may lower the risk of respiratory infections. Vitamin D may boost immune function by promoting the production of antimicrobial peptides, which help fight respiratory pathogens and may also reduce inflammation, lessening infection severity.

However, previous trials on vitamin D supplementation for respiratory infections have shown mixed results.

Study finds benefits of early vitamin D supplementation

The researchers recruited children and adolescents - aged between one and 18 years old - with data on vitamin D supplementation and serum 25-OHD levels.

Blood samples were taken to measure serum 25-OHD levels, and details on demographics, BMI, vitamin D supplementation, diet, sun exposure, sunscreen use, and history of respiratory infections were taken through questionnaires and medical records.

Vitamin D supplementation was categorized as low (<400 IU/week), moderate (400–800 IU/week), or high (>800 IU/week). Serum vitamin D levels were classified as deficient (<20 ng/mL), insufficient (20–30 ng/mL), or sufficient (>30 ng/mL).

Results showed that high vitamin D supplementation and sufficient serum 25-OHD levels corresponded with significantly lower respiratory infection rates.

For example, in the study population, 41.2% experienced respiratory infections, but only 16.7% of those on high supplementation had recurrent infections, compared to 60% in the low supplement group. 

Similarly, participants with sufficient serum 25-OHD had a 16.7% infection rate, compared to 61.4% for deficient levels.

The protective effects were strongest in children under six, which the researchers say highlights the importance of early supplementation.

They confirmed that vitamin D supplementation and sufficient serum levels independently reduced infection odds, with mechanisms likely involving enhanced immune responses, including antimicrobial peptides and cytokine modulation.

They did however note that the cross-sectional design restricts establishing causality, and temporal relationships cannot be confirmed. 

Source: Nutrients​ 2024​, 16​(22), 3953; https://doi.org/10.3390/nu16223953​
“Infections in Children and Adolescents: A Cross-Sectional Study.”
Authors: Elena Tanase, E. Et al.