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Vitamins and minerals · Answer
No. For most people, taking vitamin C regularly does not reduce how often you catch a cold, and starting it after symptoms begin does not help. Regular supplementation shortens colds slightly, by about 8% in adults and 14% in children. The exception is people under extreme physical stress, such as marathon runners, where trials found about half as many colds.
The NIH summarises placebo-controlled trials using at least 200 mg of vitamin C a day, including a Cochrane review by Douglas, Hemilä, Chalker and Treacy:
| Question | Finding | Evidence level |
|---|---|---|
| Does regular vitamin C prevent colds in the general population? | No meaningful reduction | Moderate |
| Does it shorten colds if taken regularly? | Modestly: about 8% in adults and 14% in children | Moderate |
| Does it help if started once symptoms begin? | No effect on duration or severity | Moderate |
| People under extreme exertion or cold (marathon runners, skiers, soldiers) | About 50% fewer colds at 250 mg to 1 g a day | Moderate, small number of trials |
A shorter cold by 8% means roughly half a day on a typical week-long illness. That is a small effect.
The exception in the research relates to people doing heavy, prolonged exercise or exposed to cold. If you are in a heavy build-up block, those trials used 250 mg to 1 g of vitamin C a day. However, trials did not test every kind of athlete, and many studies were small. Food, sleep, carbohydrate intake, training load and hygiene often matter more. Vitamin C is a Group B supplement in the AIS framework, meaning emerging evidence.
| Group | NIH daily RDA |
|---|---|
| Men 19 and older | 90 mg |
| Women 19 and older | 75 mg |
| Smokers | add 35 mg |
One citrus fruit, guava, a red pepper or a cup of broccoli delivers a large share of that. The upper limit for adults is 2 000 mg a day. Above that, diarrhoea is likely, and in people prone to kidney stones high intakes could raise urinary oxalate. Stones are not generally considered a risk in healthy people.
Not for general cold prevention. Many multivitamins already supply 25 to 300 mg of vitamin C (for example Dis-Chem Gold Supreme Active has 60 mg, Viridian High Five 100 mg and Solgar VM-2000 300 mg per day), which covers needs. See do multivitamins work? and which vitamins athletes need.
If a cold lasts more than about ten days, if you have a high fever, chest pain, breathlessness or ear pain, or if you are pregnant, immunocompromised, or on warfarin or other medicines, speak to a doctor or pharmacist before starting a high-dose supplement. Also see can you take too many vitamins?.
Educational information, not medical advice. Speak to a doctor, pharmacist or registered dietitian before using supplements if you are pregnant or breastfeeding, under 18, taking medication, or living with kidney, liver or heart disease. Prices were observed in October 2026 and are not offers.