EVIDENCE GUIDE

Vitamin D and Immune Function

Vitamin D is important for healthy bones and immune function. NIH notes that low vitamin D status is associated with respiratory-infection risk, while trials of supplementation have produced mixed results. Correcting inadequate intake is different from assuming that ever-higher doses provide greater protection.

What to keep in perspective

Research about an ingredient or lifestyle factor does not automatically prove that a branded supplement containing it is effective. Dose, formulation, study population and the outcome measured all matter.

Practical takeaway

Start with adequate nutrition and general health habits. If you are considering supplements because of symptoms, a suspected deficiency, medication use or a medical condition, individualized professional advice can be more useful than generalized marketing.