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.