Vitamin c and vitamin d show moderate evidence for reducing the risk of contracting upper respiratory infections (URTIs) as well as reducing the duration of URTI symptoms,[1] although only vitamin D has been shown to lower risk of the flu specifically.[2]
Have any supplements been studied for the flu?
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•Last Updated: May 16, 2025
Vitamin C and vitamin D have moderate evidence for reducing the risk of upper respiratory infections and shortening their duration, but only vitamin D has been specifically shown to lower the risk of contracting the flu.