Vitamin D is well known for its role in bone health, but it also has important functions in regulating immune responses. New research in mice suggests that vitamin D signalling may help the body control influenza infection while preventing excessive inflammation in the lungs.
A study investigated the role of the vitamin D receptor (VDR) and parathyroid hormone (PTH) during infection with H1N1 influenza A virus (Figure 1).
Figure 1: Graphical abstract.
The researchers compared normal mice with several models lacking VDR signalling, including mice specifically lacking VDR in myeloid cells such as macrophages.
Across these models, the researchers observed:
- More severe influenza symptoms and higher viral loads.
- Slower viral clearance.
- Increased immune cell accumulation and inflammatory signalling in the lungs.
- Greater mortality, with 21% mortality reported in mice lacking VDR throughout the body.
These findings suggest that vitamin D signalling helps regulate the host response to influenza, supporting viral control while limiting excessive inflammatory damage.
Myeloid cells, including macrophages, are among the first immune cells to respond to respiratory infections. The study highlights the importance of VDR expression in these cells, suggesting that vitamin D signalling contributes to the regulation of early innate immune responses.
The researchers also investigated PTH, which rises when vitamin D levels are insufficient as the body attempts to maintain calcium balance. Their findings point to contributions from both VDR signalling and PTH regulation in shaping the response to influenza.
The study highlights the delicate balance between antiviral defence and immunopathology: an immune response must be strong enough to control the virus, but appropriately regulated to avoid damaging lung tissue.
However, these findings are from mouse models and do not establish that vitamin D supplementation prevents or treats influenza in humans. The researchers emphasise that more work is needed, and taking high doses of vitamin D can be harmful.
Journal article: Tang, M., et al., 2026. Myeloid cell expression of the VDR and parathyroid hormone control the host response to influenza infection in mice, Frontiers in Immunology.
Summary by Stefan Botha
