The cold and flu season is getting underway: can vitamin C provide protection?

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A dripping nose along with a sore throat, head and joints – a cold can become a serious burden. And an expensive one: around 30 per cent of all work absences are due to the common cold. So as the cold months begin, we try to prevent it, often on our own at first. For example, commonly sold supplements such as vitamin C are popular, but is there any proof that taking extra ascorbic acid helps the body? Could it even have a negative effect? We’ve decided to get to the bottom of it:

Why does the body need vitamin C?

Vitamin C plays a role in many metabolic processes. According to the German Dietetic Association (DGE), it is required to build and maintain the structure of our connective tissue, bones and teeth. Vitamin C has an antioxidative effect, meaning it blocks damaging molecules such as free radicals, thus protecting the body. Vitamin C is already part of a healthy diet of course, with fruit and vegetables being the main providers. Major sources of vitamin C include citrus fruits, potatoes, cabbage, spinach and tomatoes.

So why take vitamin C supplements?

The belief that vitamin C supplements can fight a cold is a persistent one. 250 years ago, vitamin deficiencies were rife in Europe. Naval crews on voyages spanning months suffered from muscle wastage and rotting gums, in short: scurvy. They were unaware that they were lacking vitamin C. As the decisive substance became known through increasing research into vitamins, the consumption of ascorbic acid became commonplace. Nowadays, vitamin C deficiencies are practically non-existent in the developed world. Ascorbic acid is even added to sausages, bread and yoghurt in the form of the additive E 300, which is designed to increase shelf-life and maintain colour.

Vitamin C: the perfect defence? Proof is yet to come …

From a scientific viewpoint, there’s no evidence that routine consumption of vitamin C prevents colds. In order to support this point, researchers carried out a study on a total of 6,200 people who put their bodies under a normal amount of day-to-day stress. This means none of the participants were extreme athletes. 61 to 63 per cent had at least one cold within the space of around three months. And when the participants were given vitamin C? The rate stayed exactly the same. Therefore, there is no proof that the vitamin supplement prevents colds.

Vitamin C weakens the effects of the cold

The scientists did however make another discovery: in a period of two to four months, pre-emptively taking vitamin C can reduce the duration of a cold from ten days to seven. This was found after 6,600 people were examined in a total of ten studies, so the idea that a cold can be made milder and shorter by pre-emptively taking vitamin C is based on solid data.

And what about extreme athletes?

If we take marathon runners as an example for stress, taking a vitamin c supplement of between 250 and 1000 mg daily has the potential to prevent a cold over a period of around two to eight weeks. Studies suggest that 17 per cent of athletes suffered from a cold at least once while taking vitamin C. Without vitamin C supplements it was 35 per cent.

Can too much vitamin C be dangerous?

Taking a supplement of up to around 1000 mg of vitamin C per day in addition to dietary intake should not have any negative side effects, says the DGE. Taking 3000 mg to 4000 mg per day can lead to temporary gastro-intestinal issues such as diarrhoea. You can view a fact check examining all named studies and figures provided by AOK here.

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