The surprising backstory behind a popular cold 'remedy'

From the first hint of cold winter mornings, supermarkets and pharmacies begin heavy marketing to coax us to stock up on vitamin C to get through the cold and flu season.

As we'll see, it’s a story including a Nobel Prize winner, a book and some claims that don’t quite stack up.

Linus Pauling was a chemist from the United States who won two Nobel Prizes. One was in 1954 for chemistry, for his research into chemical bonds. The other was in 1962 for peace, for his activism against nuclear weapons testing.

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He was not a dietitian or an infectious disease physician. But that didn’t stop him publishing a book on vitamin C and colds in 1970. This book is widely credited with the skyrocketing sales of vitamin C at the time, a trend that continues today.

In this book, Pauling said we should consume high doses of vitamin C, around 1,000–2,000 milligrams a day for good health, and even more to prevent a cold.

His recommendations were said to be initially from one placebo-controlled trial in children on a ski camp in the Swiss Alps. He then analysed a further four studies conducted after his claims.

But his interpretation of these studies has been widely criticised. There were incorrect mathematical analyses, reliance on four poor-quality trials and the overemphasis of the study in children.

The short answer is not really. Multiple studies conducted since the ones Pauling analysed show that if there is an effect on vitamin C and colds, it’s minimal. Even then, any marginal benefits are only under certain circumstances, such as if you’re an athlete or in the army.

One study, published in 2023, was a meta-analysis that combined the results of ten placebo-controlled trials. These looked at the effect of vitamin C on the severity and duration of colds. In total, these trials involved 2,736 healthy people (adults, children and athletes) who regularly took at least 1,000mg of vitamin C a day, not just when they had a cold.

Overall, the researchers found people who took vitamin C had a 15 per cent reduction in severe cold symptoms compared to those who didn’t take it. This was expressed as the number of days "confined indoors", which the authors acknowledged as a limitation. Vitamin C did not affect how long mild symptoms lasted.

A meta-analysis in 2013 found taking lower doses (at around 200mg a day) did not decrease the number of colds in the general population. However, there were fewer colds for athletes and army personnel.

Similar to the other study, regular vitamin C supplements showed a reduction in severity of symptoms in children and adults by 8–14 per cent. However, taking vitamin C at the start of the cold had no benefit.

So, from these two meta-analyses, Pauling’s original advice is over-stated. There is no evidence vitamin C will reduce your risk of catching a cold.