This winter, most of us will catch a cold. Our kids will probably catch at least two or three. We all know you are supposed to feed a cold and starve a fever. But does it really make any difference if they eat or not?
Cold picture from Shutterstock
This proverb appears to have become popular in the nineteenth century. However, dozens of websites attribute the phrase back to the fourteenth century and Geoffrey Chaucer's Canterbury Tales. But no such phrase exists by Chaucer. It seems that everyone simply copied a story, without checking its original source. This is also how many medical myths start.
Colds are caused by viruses that infect the nose, sinuses and throat. But the unpleasant symptoms (blocked and runny nose, cough, sneezing, sore throat and headache) are largely triggered by our body's reaction to them, rather than any damage caused by these bugs.
The runny nose (often accompanied by sneezing) is caused by increased secretions from the glands in the nose and seepage of serum (the yellow cell-free part of blood) into the nose.
Progressively, white blood cells also find their way in and their presence causes the gunk coming out your nose to turn yellow or green, as these cells contain a green protein called myeloperoxidase. This change in colour is not caused by bacteria and does not mean you need to take antibiotics.
The blocked nose comes about as the large veins in your nose dilate to narrow the space available for air to flow, while at the same time, the volume of secretions are increased and their clearance is diminished, especially during the latter phases of a cold.
Curiously, one nostril is usually worse than the other, at any one time. And it's not always the same one. In fact, which nasal passage is most blocked usually alternates from one to the other over a period of several hours. This so-called "nasal cycle" is thought to be defensive response, possibly to keep one open while the other one is being pumped clean with protective fluids.
When you have a cold you often don't feel much like eating anything. This is the result of chemicals released by your body to fight off infection also affecting your brain. These same chemicals can also make you feel irritable, lethargic, or just plain miserable.
But why should your brain want you to starve if you are ill? One reason may be that you don't want to waste precious energy finding food that you could otherwise use in getting well? Of course this theory doesn't wash if Mum has just made you chicken soup. But the modern brain still works much like a caveman's did.
In fact, if you force-feed mice during an infection they are actually more likely to die than if they only eat what they feel like.
These facts have led to the idea that there may have been a semantic shift in the idiom. What we think of as "feed a cold, starve a fever" may originally have been "fede a cold starb o'feber" (fede = "stoke [a fire]", starb = "die", feber = "fever") or "stoke the inflammation of an infection and you die".
But while starving (in the short term) can keep a feverish mouse alive, this may have little relevance to an innocuous cold.
Most times grown-ups get a cold they don't even get a temperature. Adults generally save fevers for bugs they've never seen before or severe infections, like influenza.
So you have a sore throat and a runny nose, but no fever or cough from the beginning, you're probably just coming down with a common cold. And so you may just as well feed (during) your cold, and save your starving for the fever.
For kids all bugs are new, so fevers are commonplace. This doesn't mean they're in any danger, but they'll probably be more miserable than you are.
Whether or not you are feeding a cold or starving it makes little difference to the biology of a common cold. In the end, most colds are mercifully short lived and will peter out after a week or so, regardless.
But feeling healthy is much more than biology. When you've got a cold, food is essentially a comfort not a cure. And at these times we all could use some of that.
Merlin Thomas is Adjunct Professor of Preventive Medicine at Baker IDI Heart & Diabetes Institute. He does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.
Rebecca McNamara contributed to this article. She works for the Australian Research Council Centre of Excellence for the History of Emotions (Europe 1100-1800). She receives funding from the Australian Research Council. She works at the University of Sydney.