Experts explain the facts behind vitamin C, vitamin D and zinc for avoiding illness

Two professors have addressed common misconceptions about using vitamins to help prevent colds.

You only have to scroll a little way through social media to be bombarded with pills, drinks and supplements claiming that without vitamins X, Y or Z, you are bound to fall ill.

So what is actually true? Two professors have now weighed in on some of the biggest claims and which, if any, may help keep you from getting sick, especially during the colder months.

Warnings such as not going out with wet hair or you will “catch your death” are familiar to many people, especially from childhood. But are they true, or just myths that have been passed down for years?

Social media can sometimes sound much like those old warnings, only on a much larger scale.

Vitamin C, vitamin D and zinc are among the most talked-about supplements, with vitamin C often praised for helping to ward off colds. But which of them actually helps against an approaching flu or cold?

During an appearance on the ZOE Science & Nutrition Podcast, Professor Daniel Davis said the idea that vitamin C protects against colds is really “a 50-year-old myth”.

And vitamin C is not the only claim that needs unpacking.

The reality about vitamin supplements and taking vitamin C, D and zinc

Professor Davis said that while vitamin C is “important for health in lots of ways,” its role in preventing colds is an “absolute myth.”

“High doses won't stop you catching a cold,” he said.

He added that if someone takes a “high dose of vitamin C,” they may, on average, get over a cold about eight percent quicker. Even so, it is difficult to know for certain because people often take more than one supplement at the same time.

On zinc, Prof. Davis said he does not “think there's any clear evidence around” it.

When it comes to vitamin D, the picture is slightly different.

Professor Tim Spector said the evidence changes over time, but that there is currently some weak support for the idea that having high vitamin D levels may slightly reduce the risk of respiratory infections, by around 10 percent.

Prof. Davis echoed that point, saying the benefit appears small, though the NHS does advise that people may consider taking vitamin D during the winter months.

“Everything else, slightly depends on whether you're really deficient at the beginning,” Spector added. “There’s very little data to show that if you've got normal levels that supplements really, really help you and prevent an illness.”

So what actually lowers the chances of catching a cold?

Professor Davis said people are more likely to get colds in colder months because viruses can survive for longer in low temperatures.

He said the best defence lies in diet.

“If you have a healthy gut, then you're much more likely to have a healthy, well-balanced immune system,” Prof. Davis said.

He also noted that mucus is an important part of the body’s defence, explaining that it contains a mixture of molecules, including some that can directly destroy viruses.