Don’t rely on vitamin C to prevent colds
Taking vitamin C every day will basically not make you catch fewer colds, and starting only after you already have a cold works only sometimes. Daily use can shorten one cold by about 8%; whether 300 to 500 a year is worth it is your call. Marathon runners and soldiers marching in cold regions are the exception: among them, those who take it get about half as many colds.
Each effervescent tablet costs roughly 1–2 yuan;
Cochrane’s pooled analysis of 29 trials with 11306 participants indicates that regular vitamin C consumption d…
Each effervescent tablet costs roughly 1–2 yuan; annual expense ranges from 300 to 700 yuan.
Cochrane’s pooled analysis of 29 trials with 11306 participants indicates that regular vitamin C consumption does not meaningfully lower overall cold incidence; the relative risk is 0.97 (95% CI 0.94–1.00). For trials where vitamin C was taken after cold onset, results varied widely — some showed benefit while others did not. Among participants who took it regularly, the average cold duration decreased by 8% in adults (95% CI 3%–12%) and 14% in children (7%–21%). Marathon runners, skiers, and soldiers in cold environments again represent the exception: five trials with 598 participants demonstrated that vitamin C intake reduced cold incidence by half (RR 0.48; 95% CI 0.35–0.64). Its perceived value stems largely from its low cost, pleasant taste, and the long-standing belief that vitamin C prevents colds.
Hemilä H, Chalker E (2013). Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. https://doi.org/10.1002/14651858.CD000980.pub4
Open source linkControversy: The same review confirms that regular vitamin C intake does shorten cold duration — by 8% in adults (3%–12%) and 14% in children (7%–21%), equating to roughly half a day of reduced illness per cold episode. Marathon runners, skiers, and soldiers in cold climates remain the exception; five trials involving 598 subjects show a 50% reduction in cold incidence (RR 0.48; 95% CI 0.35–0.64). The vast majority of people do not fall into these categories.