Do you really need to take a vitamin C tablet to ward off a winter cold? Top scientist reveals the few supplements that could give you a flu-free season

The season of coughs and colds is officially upon us.

Experts say that the bombardment of winter bugs has started earlier this year, with unusually high cases of flu in September. 

But is being stuck in bed with a runny nose and aching throat inevitable, or is there something you can do to ward off sickness?

Turn to social media and you’ll see a deluge of videos whereby health gurus demonstrate their favourite cold prevention strategy. And there’s one supplement that’s a common feature: vitamin C. 

Often thought of as immune boosting, the nutrient – abundant in citrus fruits – is indeed vital for fighting off infections, according to the The European Food Safety Authority (EFSA)

The NHS recommends that adults need 40 milligrams (mg) of vitamin C a day. That’s the equivalent of half an orange, one red pepper or, surprisingly, one-and-a-half baked potatoes.

But, according to recent research by scientists at Ulster University, one in five Britons don’t even get that. 

So will taking vitamin C supplement give us the boost we need to stay flu-free this winter? Here, experts reveal the answer – along with the two other vitamins that could help.

Will taking a vitamin C supplement prevent colds?

While extensive research has found that taking a vitamin C doesn’t ward of sniffles for the majority of people, there’s a subset who may benefit.

‘Five trials have shows that vitamin c supplementation can halve the incidence of colds in people undergoing extreme physical stress – such as endurance sport like running,’ says Professor Adrian Gombart, a professor of biochemistry and biophysics at Oregon State University in the US.

Specifically, the studies involved participants taking between 1,000 mg and 2,000 mg per day, and starting supplementation at least two weeks before the physical activity. 

The researchers added that those undergoing extreme physical demands may be particularly susceptible to respiratory infections, and therefore see the biggest benefit from a vitamin boost.

For everyone else though, the chances of protection are slim.

A major review in the journal Cochrane involving 29 trial comparisons and 11,306 participants found that regular ingestion of vitamin C had no effect on common cold incidence in the ordinary population. In each trial participants were taking at least 0.2 g (200 mg) of vitamin C a day.

Will a vitamin C supplement make my cold shorter – or less wretched?

The duration and severity of common cold symptoms could indeed be shortened with supplementation, science suggests. 

In a 2023 Cochraine review published in the BMC Public Health journal, oral doses of at least 1000 mg cut the severity of common cold symptoms by 15 per cent, compared to taking a placebo supplement.

Professor Gombart adds: ‘Vitamin C supplementation shortened the duration of severe, but not mild, symptoms.

‘How it might work is not well understood, but the antioxidants in the nutrient may help limit tissue damage in the body’s protective linings, including the nose, mouth and respiratory tract.’

The Cochrane review also discovered that regular vitamin C supplementation resulted in a 14 per cent reduction in cold duration in children and in 8 per cent in adults.

‘That would translate into about one day less for children and half a day less for adults in the case of a typical cold that lasts about a week,’ adds Professor Gombart.

However, benefits have only been found in those who have been taking vitamin C supplements prior to getting a cold – not during the illness.

Is an orange-a-day the same as a vitamin C pill?

‘Taking additional vitamin C to avoid catching the cold is probably not worthwhile if you are already getting enough in your diet,’ says Professor Gombart. 

‘But if you think you’re lacking, taking a supplement could modestly reduce the average duration of your cold.’

Prof Gombart recommends consuming more than the modest 40mg that’s often recommended.

In fact, he and colleagues advise a daily intake of 400 mg per day to maintain adequate levels in the body’s tissues – preferably from dietary sources.

‘If people find it difficult to reach this intake level, then a supplement can help,’ says Professor Gombar.

Experts advise limiting vitamin C to 1000mg a day, as the nutrient can cause pleasant  side effects like diarrhoea or stomach pain in high doses. 

Are there any other supplements that can stop a cold attacking?

One mineral that’s come under the spotlight in recent years for its bug-fighting properties is zinc. 

The nutrient – found in seafood, red meat, poultry and dairy products – exploded in popularity after the publication of a 2016 study that appeared to suggest a special type of fast-dissolving zinc lozenge could reduce cold duration by three days.

Indeed, the NHS says that it’s important for keeping your immune system strong so you can fight off sickness.

But Prof Gombart says positive findings are not so straight forward. 

 ‘A 2024 review of 34 studies found that zinc might shorten colds by about two days on average, but the evidence was rated of “low certainty” because results varied greatly across trials. 

‘Whether zinc reduces overall symptom severity is unclear, and taking it routinely to prevent colds showed little or no benefit.’

Prof Gombart adds that the zinc doses used in trials is often far higher than the tolerable upper intake level and shouldn’t be used long term.

Taking more than 25mg of zinc supplements a day could cause problems such as anaemia and weak bones, the NHS warns.   

For reference, there’s about 7-10mg of zinc in a typical steak.

According to Dr Dinta Thakkar, a GP at Bupa Health Clinics, vitamin D is definitely worth considering for an immune system boost.

‘While taking vitamin D is not a guaranteed way to prevent colds, maintaining healthy levels may help your immune system do its job,’ she says. 

 ‘Adults should consider taking a daily 10 microgram (400IU) vitamin D supplement during the autumn and winter months from October through to March.’

The so-called sunshine vitamin is produced when ultraviolet B (UVB) rays from sunlight trigger a chemical reaction in the skin. This means that, particularly in the winter months, around one in five Britons don’t get enough. 

Realistically, there isn’t a supplement that will stop you from catching a cold – although vitamin C, zinc and vitamin D can all help to support your immune system to potentially clear it quickly. 

‘Eating well, sleeping enough and exercising often, and practicing good hygiene can reduce your risk too – and shouldn’t be dismissed,’ says Dr Thakkar.