High-dose vitamin C doesn’t stop colds, but may slightly shorten severe symptoms

Linus Pauling, a Nobel laureate in chemistry and peace, popularized the idea that massive vitamin C doses prevent colds in his 1970 book, despite his lack of expertise in nutrition or infectious disease. Subsequent large-scale studies and two meta-analyses (2013 and 2023) have found that regular supplementation of 1,000 mg or more does not lower the chance of catching a cold, and only marginally lessens the severity of symptoms—roughly a 15% reduction in days spent with severe illness.

The effect is most noticeable in specific groups such as athletes and army personnel, while starting vitamin C at the onset of a cold provides no benefit. Daily intakes above 1,000 mg can lead to diarrhea, stomach cramps, increased oxalate excretion, and interactions with certain medications. Health authorities in the United States set an upper safe limit of 2,000 mg, whereas Australian guidelines advise staying below 1,000 mg. Experts recommend consulting a GP before using high-dose supplements, noting that less than 4% of Australians are deficient in vitamin C.