FactSentinel

The adage "feed a cold, starve a fever" is not supported by medical evidence, and thermometer readings, whether from mercury or modern digital devices, have never shown that eating less is the right response to a fever. A thermometer measures body temperature only. It says nothing about what a sick person should or should not eat. The saying is a folk belief that predates modern medicine, and the claim that mercury thermometer readings back it up has no scientific basis.

Current medical guidance points the other way. Fever raises the body's metabolic rate, so it increases the need for energy and fluids. Dehydration is a particular risk because fever causes fluid loss through sweating and faster breathing. Health organizations generally recommend drinking plenty of fluids and eating nourishing food as appetite allows, whether the illness is a cold, the flu, or another infection. Both colds and fevers are best managed with rest, hydration, and adequate nutrition. Little evidence supports deliberately restricting food in either case.

The proverb is often traced to a 1574 dictionary entry, and the idea that it distinguishes between types of illness has been repeated for centuries. Some researchers have speculated that eating might affect immune signaling differently in viral and bacterial infections, but this has been tested mainly in animals and is not a basis for advice to people. A related misconception is that a fever is itself an illness. It is usually a sign that the immune system is responding to infection. Mercury thermometers, now largely phased out because of toxicity concerns, were simply an older way to measure it.