Vitamin C won’t prevent most colds, but it may do one small thing
The belief that huge doses of vitamin C can ward off colds was popularized more than 50 years ago by Nobel Prize winner Linus Pauling. Since then, larger studies have found that vitamin C does not prevent most people from catching a cold, although regularly taking it may make severe symptoms slightly shorter or milder.
Supermarkets and pharmacies ramp up their marketing of vitamin C as winter approaches, but the evidence supporting its effectiveness against colds is weak. Linus Pauling, a Nobel Prize-winning chemist, popularized the idea of taking high doses of vitamin C to prevent colds in a 1970 book, citing a single placebo-controlled trial.
However, subsequent studies have been criticized for flawed analysis and reliance on poor-quality research. A 2023 meta-analysis of 10 placebo-controlled trials involving 2,736 healthy individuals found that regular intake of at least 1,000mg of vitamin C per day reduced the severity of cold symptoms by 15% on average, measured as reduced indoor confinement days.
However, vitamin C did not impact the duration of mild symptoms. Lower doses (around 200mg) did not decrease the number of colds in the general population, but showed benefits for athletes and those in the military. Taking vitamin C at the onset of a cold had no effect. The recommended daily intake of vitamin C is 45mg for adults in Australia, equivalent to half an orange or three florets of broccoli, to minimize the risk of adverse events associated with high-dose supplementation.
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