PH
Vitamin C is essential for health, but routinely taking it doesn't mean you'll stop catching ordinary colds.
Large reviews have found that regular vitamin C supplementation generally doesn't reduce cold incidence in the general population, although it may modestly shorten the duration or severity of colds in some circumstances.
Starting supplements only after symptoms begin hasn't consistently shown substantial benefit.
People still need adequate vitamin C as part of normal nutrition.
“Important for your immune system” doesn't mean “makes you immune to colds.”
© Cochrane