Vitamins C and D support normal immune function, but neither is a guaranteed cold remedy. Find out what the research says, how much you need and how to support your immune system.
🕒 7 min read
Up to 200 different viruses can infect the upper respiratory tract to cause symptoms of the common cold. Inflammation of the lining of the nose, throat and sinuses leads to the typical symptoms of sore throat, runny, stuffed-up nose, watering eyes, coughing and sneezing. Most people start to feel better within one to two weeks.1
Cold viruses are highly infectious and spread from person to person through coughing, sneezing and contact with shed viruses, which can survive on door handles, tissues and other surfaces for at least 24 hours. Good hygiene is therefore vital to limit the transmission of cold viruses.
How long does a cold last?
Most people start to feel better within one to two weeks. Rest, plenty of fluids and suitable symptom relief can help while you recover.1
Supporting your immune system against colds
Maintaining a healthy immune system helps your body respond to infections, but it does not guarantee that you will avoid a cold.
Good nutrition is key. Aim to eat a healthy, varied diet that supplies wholegrains, beans, 5-a-day fruit and vegetables, seafood and olive oil. Eating well supports normal immune function; no single food is a guaranteed defence against cold viruses.
A varied diet provides nutrients needed for normal immune function, including vitamins A, B12, B6, C and D, folate, copper, iron, selenium and zinc.
Vitamin C and vitamin D: support for normal immunity
Both vitamins contribute to the normal function of the immune system. That nutritional role is different from showing that a supplement prevents or treats a cold. A supplement can help top up intake when needed, alongside a varied, balanced diet.
Does vitamin C help with colds?
Vitamin C contributes to normal immune function and helps protect cells from oxidative stress. Researchers have also studied whether supplements affect the likelihood, duration and severity of colds.
A Cochrane review found that regular vitamin C supplements did not reduce the chance of catching a cold in the general population. They did modestly shorten cold duration on average. Starting vitamin C after symptoms began showed no consistent benefit.2
Some benefit in preventing colds was seen in people exposed to brief periods of extreme physical stress, such as marathon runners. This finding should not be assumed to apply to everyday life. The NHS says there is little evidence that vitamin C supplements prevent colds or help people get better more quickly.1
Vitamin C is present in plenty of fresh fruit and vegetables. A varied diet can usually meet your daily needs.
How much vitamin C do you need?
NHS guidance says adults aged 19 to 64 need 40mg of vitamin C daily. You should usually be able to get this from a varied, balanced diet. The 80mg nutrient reference value shown on supplement labels is a labelling reference, rather than a dose for treating colds.3
If you choose a supplement to top up your intake, follow the directions. Explore our Vitamin C range; higher doses do not guarantee faster recovery.
What foods contain vitamin C?
Vitamin C is found in many fruit and vegetables, especially citrus fruit, berries, blackcurrants, peppers, kiwi fruit and green leafy vegetables. Broccoli, Brussels sprouts and potatoes also contribute. Include a variety every day, as vitamin C cannot be stored in the body.3
Can you take too much vitamin C?
Taking more than 1,000mg daily can cause stomach pain, diarrhoea and wind. Follow the label and check your total intake if you use more than one supplement.3
Does vitamin D help prevent colds?
Vitamin D contributes to normal immune function, and immune cells have receptors that respond to it. However, low vitamin D levels being associated with infections does not prove that taking more prevents them.
In the UK CORONAVIT trial, offering vitamin D testing and supplements did not reduce the risk of acute respiratory infections. Vitamin D should therefore be considered for meeting nutritional needs, rather than as a proven cold-prevention treatment.5
Explore our Vitamin D range and read how to increase your vitamin D levels.
What foods contain vitamin D?
Food sources of vitamin D include oily fish, egg yolks and fortified foods such as some spreads and breakfast cereals. Check plant-based drink labels for fortification. UK cows’ milk is generally not a good source. See our guide to vitamin D in food.4
How much vitamin D do you need?
Although diet should always come first, getting enough vitamin D from food alone can be difficult. The NHS advises adults to consider 10mcg (400 IU) daily in autumn and winter, or throughout the year if they have little sun exposure or darker skin.4
A diagnosed deficiency may need a different dose prescribed by a healthcare professional. Higher doses are not routinely required simply because you have a cold.
Gummies and sprays are available for those who prefer not to take tablets.
Is vitamin D3 the same as vitamin D2?
Vitamin D2 and D3 are two forms of vitamin D. D3 can come from animal sources or vegan sources such as algae and lichen. Choose a suitable formulation and follow its label; see our vegan vitamin D3 guide.
Can you have too much vitamin D?
Too much vitamin D can cause calcium to build up in the blood. Adults should not take more than 100mcg (4,000 IU) a day unless advised by a doctor. Check the total across supplements and follow the label.4
When to seek advice about a cold
Contact your GP if symptoms worsen, do not improve after 10 days, or you have a high temperature for more than three days. Seek advice if you have chest pain, shortness of breath, a weakened immune system or a long-term medical condition.1
Ask a pharmacist about suitable symptom relief. Check with a healthcare professional before using supplements if you take prescribed medicines, are pregnant or breastfeeding, or have a medical condition.
