Is it true that … you should feed a cold and starve a fever?

Tom Wilkinson, professor of respiratory medicine at the University of Southampton, says there is some truth to this age-old saying. When you get a respiratory viral infection, otherwise known as a cold, your immune system is activated, he explains. Your ability to fight it off depends on how strong your system’s responses are – and you need to be fuelled up in order to respond well.

“Activated immune cells are among the most metabolically demanding – they take a lot of energy from the body,” Wilkinson says. That means you ideally need to be consuming nutrient-dense, calorie-rich foods. He refers to an experiment in which randomised volunteers were either given a liquid meal or starved for 24 hours. Those who were fed displayed a more robust immune system.

“Going on a diet as you’re developing a cold is probably not the best idea,” he advises. It’s especially important to keep up your calorie intake if your immune system is compromised. Also, if you are frail or malnourished, “you may have an increased requirement for nutrients”.

As for starving a fever? One theory is that this could be a mistranslation, Wilkinson says, and the original phrase was “feed a cold, stave off a fever”, as proper nourishment may help prevent secondary infections.

“We do often lose our appetite when we have a fever,” he adds, although the “jury is out” as to whether this indicates a positive response. “Some evidence suggests that starvation may have an effect on immune responses, but that’s not proven. I wouldn’t suggest that you start starving yourself.”

The takeaway? Your immune system needs energy and nutrients to work efficiently, so eat a balanced diet. And hydration is important, too, Wilkinson says: “There’s lots of evidence that it improves outcomes.”