Synopsis

Source of validity: Scientific
Rating (out of 5): 3

Vitamin D has been studied for its role in supporting immune function and potentially reducing the risk or severity of respiratory tract infections, including the common cold. Several observational studies have noted that individuals with lower vitamin D levels may be more susceptible to colds and other respiratory illnesses. Mechanistically, vitamin D is thought to enhance the pathogen-fighting effects of monocytes and macrophages—white blood cells that are important parts of the immune defense—and decrease inflammation.

Multiple randomized controlled trials (RCTs) and meta-analyses have explored vitamin D supplementation for the prevention of respiratory infections. A widely cited 2017 meta-analysis published in the BMJ found that vitamin D supplementation was associated with a modest reduction in the risk of acute respiratory tract infections, particularly among individuals who were deficient in vitamin D. However, the effect size was small, and some later studies have shown less clear or inconsistent results, especially in populations with adequate baseline vitamin D levels.

Overall, while there is scientific evidence supporting a potential benefit of vitamin D supplementation in reducing the risk of respiratory infections such as colds, the strength of evidence is moderate (rated 3/5). The benefit appears most pronounced in individuals who are vitamin D deficient, and routine supplementation in those with adequate levels may have limited impact on cold prevention.

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Other ingredients used for Colds (general)

Other health conditions supported by vitamin D

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