Vitamin C: A cure for your cold?

Vitamin C is what lots of us reach for when we’re feeling ill, with the hope it’ll give our immune systems a boost.

While its ability to fight a cold is debatable (sorry), this vitamin does help us resist infection and also plays a part in regulating inflammation when the body is under physical stress.

Vitamin C acts as an antioxidant, helping to protect cells by neutralising free radicals. Left unchecked, these free radicals (which are produced by our bodies) can damage cells and DNA. It’s also great for skin health as it plays a role in the synthesis of collagen, the main structural protein in our skin and connective tissue.

It helps us absorb iron, too. This is especially important for people following plant-based diets, because iron from plants is harder to absorb than from animals.

How much vitamin C do I need?

Unlike some other vitamins, our bodies can’t produce vitamin C, so we need to get it through our diet.

In the UK, the recommended intake for adults is 40 milligrams (mg) a day. That climbs to 50mg during pregnancy and 70mg when breastfeeding.

These guidelines were set in 1991 and are designed to prevent deficiency. But other guidelines suggest that optimal intakes are higher: European recommendations, for instance, are 110mg a day for men and 95mg a day for women.

People who smoke will need more vitamin C. That’s because smoking creates free radicals and depletes vitamin C. There are no guidelines for smokers in the UK, but US recommendations suggest an additional 35mg a day.

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Am I getting enough vitamin C?

You should be able to get enough of this vitamin from a healthy balanced diet that includes plenty of fruit and vegetables (a medium orange contains over 80mg). The problem? UK adults aren’t eating the recommended five-a-day.

It’s unsurprising, then, that data from the most recent National Diet and Nutrition Survey (a large, ongoing survey of the UK’s nutrition intake) suggests that almost a quarter of adults don’t get enough vitamin C.

The survey also found that the five biggest contributors to vitamin C intake were fruits, cooked vegetables, smoothies, fruit juice and sugar-sweetened soft drinks.

If you think soft drinks sound like an unusual source of vitamin C you’re right – it’s usually added by the producer.

What happens if I don’t get enough?

Scurvy isn’t just a historical ailment of sailors from centuries ago. It’s the name for severe vitamin C deficiency and, while it’s rare in the UK, there has been an increase in cases over recent years.

This is linked with rising food prices and a lack of access to fruit and vegetables for people living in deprived areas.

Symptoms of scurvy include:

• Tiredness and low energy
• Low mood
• Inflamed and bleeding gums
• Skin that bruises easily
• Slow-healing wounds
• Joint and muscle pain

The human body has around 1,500mg of vitamin C in total, and signs of scurvy appear when levels fall to around 350mg. But for this to happen, you’d need to consume little to no vitamin C for four to 12 weeks.

Research suggests the risk of low vitamin C levels increases with:

• A prolonged lack of fresh fruits and vegetables
• A ‘tea and toast’ diet, more common in older adults living alone with limited access to nutritious food
• Smoking
• Excessive alcohol intake
• Conditions that can affect vitamin C absorption, like Crohn’s disease

Which foods are a good source of vitamin C?

Many fruits and vegetables are high in vitamin C, especially citrus fruits and soft fruits like oranges and strawberries, and leafy green vegetables like spinach and kale.

How to boost your vitamin C intake

Focus on eating five varied portions of fruits and vegetables a day. For example, an orange with breakfast, a bowl of leafy greens with a sandwich at lunch, broccoli and peas with your evening meal and a handful of strawberries for pudding will provide more than 200mg of vitamin C.

Also think about how you store and cook fruit and vegetables. Vitamin C levels in food fall during cooking and with prolonged storage.

To get the most vitamin C from fruits and vegetables, choose steaming or stir-frying instead of boiling your veg, aim to eat raw leafy greens like watercress and spinach, and try to make sure your fruit and veg is as fresh as possible – or buy frozen.

Can extra vitamin C help treat a cold?

Vitamin C has been sold as a cold remedy for decades, but a review of 29 studies found no convincing evidence that taking vitamin C supplements regularly prevents colds.

There is some evidence that it might slightly reduce the duration of a cold, but only by around 8%. So for a cold that lasts a week, that’s around half a day.

People who seemed to benefit more from supplements were those under extreme physical stress, like marathon runners or those training in cold temperatures. In these cases, taking a vitamin C supplement two to three weeks before the intense training exercise reduced the risk of developing a cold by half.

Taking more than 1,000mg (one gram) a day of vitamin C has been linked with diarrhoea and stomach cramps. At doses above one gram, absorption also falls to less than 50%, and anything your body doesn’t absorb is flushed out in urine, so mega doses offer little benefit.

Originally published October 2025

Laura Tilt is a registered dietitian with a master’s in public health nutrition and a postgraduate diploma in dietetics. Since qualifying in 2012, she has specialised in gastroenterology at London’s UCLH before moving into freelance practice. With over 10 years of experience translating nutrition science into accessible, meaningful advice, Laura’s specialist interests include digestive health, disordered eating, and sports nutrition.

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