The Claim
Serum vitamin D levels below 50 nmol/L are associated with increased susceptibility to respiratory infections and impaired immune cell activation in populations with limited sun exposure or chronic disease, due to the role of calcitriol in modulating T-cell and macrophage function.
What the research says
Roughly balanced
Support and challenge are close. The picture may shift as more studies come in.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
People with serum vitamin D levels below 50 nmol/L have a higher risk of respiratory infections and reduced immune cell activity, particularly if they have limited sun exposure or chronic disease, because calcitriol influences T-cell and macrophage function.
See the scientific wording
Serum vitamin D levels below 50 nmol/L are associated with increased susceptibility to respiratory infections and impaired immune cell activation, particularly in populations with limited sun exposure or chronic disease, due to calcitriol's role in modulating T-cell and macrophage function.
When vitamin D levels are low, the body makes less of its active form, calcitriol, which normally tells immune cells in the lungs and airways to produce natural antibiotics and calm down excessive inflammation. Without enough calcitriol, these immune cells cannot kill viruses and bacteria as effectively, and they become overactive, damaging tissue and making it easier for infections to take hold.
What the research says
1 studyThis study says vitamin D helps your body’s defense system work better, so if you don’t have enough of it, you might get sick more often — especially if you don’t get much sun or have other health problems.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.