Do vitamin C and zinc work for colds?
No, they won’t stop most colds. But each may make one shorter, and the catch is timing. Vitamin C only helped when taken daily before a cold. Zinc only helped once one started.
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Do vitamin C and zinc work for colds?
Not to stop one. The NHS says there’s little evidence that supplements such as vitamin C prevent colds or help you get better more quickly.
The big reviews agree. Across 10,708 people, daily vitamin C made almost no difference to who caught a cold. Zinc taken to prevent colds showed little or no drop either.
Making a cold shorter is a different story. Each may help a little, at a different time.
| When you take it | Vitamin C | Zinc |
|---|---|---|
| Regularly, before a cold | Daily, at least 200mg: colds 8% shorter in adults and 14% shorter in children. | Little or no fewer colds. Probably no shorter. |
| Once a cold starts | No clear effect. | About 2.4 days shorter on average. Low-certainty evidence. |
Sources: Cochrane: vitamin C; Cochrane: zinc
Your next step: decide what you want. To stop colds, neither is worth buying. For a shorter cold, the timing and dose below matter.
When should you take vitamin C and zinc?
That’s the timing catch. Vitamin C only shortened colds when people took it every day (at least 200mg in the trials), before they got ill. Starting it once a cold began showed no consistent effect.
Sources: Cochrane: vitamin C; Cochrane: zinc; NHS
One group did catch fewer colds on daily vitamin C. In 598 marathon runners, skiers and soldiers training in freezing conditions, colds were about halved.
Most trials that treated colds with zinc used lozenges, sweets that dissolve slowly in your mouth.
Your move: if you take vitamin C for colds, it only counted as a daily habit. Even so, the review authors say routine vitamin C isn’t justified for most people. As it’s cheap and safe, they say it may be worth testing whether it helps you at the start of a cold.
Should you take vitamin C and zinc together?
Very little research tests the pair. The Cochrane zinc review left out zinc mixed with vitamins, so it tells you nothing about combined tablets.
The only study we found pooled two small trials of 1,000mg vitamin C plus 10mg zinc, in 94 people with colds. Over 5 days, the pair eased a runny nose better than a dummy pill.
Neither trial showed a clear effect on its own. The authors call them preliminary, and the lead author worked for a supplement maker.
That 10mg of zinc is also far less than the lozenge trials used. Buying a combined tablet? Check both amounts against the NHS limits below.
How much vitamin C and zinc is safe?
| Nutrient | Adults need | NHS supplement limit |
|---|---|---|
| Vitamin C | 40mg a day (ages 19 to 64). | Less than 1,000mg a day is unlikely to cause any harm. |
| Zinc | About 9.5mg a day for men (ages 19 to 64), 7mg for women. | No more than 25mg a day, unless a doctor advises it. |
Sources: NHS: vitamin C; NHS: zinc
Here’s the catch with zinc. Lozenge trials that made colds about a third shorter used over 75mg a day. That’s more than 3 times the NHS limit.
High doses of zinc cut the copper your body can absorb. The NHS says this can lead to anaemia (too few red blood cells) and weaker bones.
Zinc for a cold also probably brings more mild side effects. The review looked for a bad taste, loss of smell, being sick, stomach cramps and diarrhoea.
Vitamin C over 1,000mg a day can cause stomach pain, diarrhoea and wind. These should stop once you stop the tablets.
Want more than 25mg of zinc a day? Ask your GP first.
For label maths, see zinc supplement dosage. Taking iron too? See vitamin C and iron.
What helps a cold get better?
Time, mostly. The NHS says you should begin to feel better in about 1 to 2 weeks.
NHS steps to ease a cold this week
- Get plenty of rest.
- Drink lots of fluid, such as water.
- Gargle salt water for a sore throat (not for children).
- Squeeze half a lemon into a mug of boiled water and add 1 to 2 teaspoons of honey. No hot drinks for small children, and no honey for babies under 12 months.
- Breathe in steam to ease a blocked nose, such as in the bathroom with a hot shower running. Never let children breathe steam from a bowl of hot water.
- Ask a pharmacist about paracetamol, ibuprofen or a decongestant (a medicine that unblocks your nose). Decongestants are not for children under 6.
Source: NHS: common cold
Don’t use a shop-bought nasal spray for more than a week. It can make symptoms worse.
Antibiotics won’t help. Colds are caused by viruses, and antibiotics only work on bacteria.
Want vitamin C from food? Oranges, peppers, strawberries, broccoli and potatoes are all good sources. Never stop or change a prescribed medicine without your prescriber.
Weighing up other pills? See supplements worth taking and do I need a multivitamin.
When to speak to a GP
You can usually treat a cold at home. The NHS says see a GP if:
- You’ve had a high temperature for more than 3 days, it’s very high, or you feel hot, cold or shivery.
- Your symptoms get worse, or don’t get better after 10 days.
- You feel short of breath, have chest pain, or have a cough for more than 3 weeks.
- You have a long-term condition, such as diabetes or a heart, lung or kidney condition, or a weak immune system, such as from chemotherapy.
- You’re worried about your child’s cold symptoms.
Catching one cold after another? See immune system blood tests.