Are you feeling under the weather? Why not feed a cold and starve a fever…or is it starve a cold feed a fever? Somewhere along the line, the phrasing of this popular dictum got switched around to ‘feed a fever starve a cold,’ adding more puzzlement to an already befuddled issue.

‘Starve a fever feed a cold’ is the original logic, dating back to the pre-scientific Dark Ages. Although the precise origin of the advice is not known, we do know of a dictionary author named John Withals who included a snippet in his 1574 reference manual. “Fasting is a great remedie of feuer,” he wrote with the best of intentions.

Sixteenth century medieval physicians believed that a “cold” was the consequence of a drop in body temperature, and a “fever,” conversely, the result of a temperature spike. It made sense then, to try and warm up individuals struck with a cold. Those with a fever should simply cool off. Physicians thus advised patients to either eat or not eat, depending on their condition. After all, eating does increase body temperature. Hence: Feed a cold starve a fever.

Is there any scientific evidence to verify the old bedside wisdom? Today, we know that colds and fevers are not opposing conditions, and that the temperature regulation mechanisms at work are much more complicated than the adage admits. Let’s examine each part of this bromine to determine whether it’s a full truth, a half-truth or merely a dead-wrong urban myth.

Why Not ‘Starve a Fever’?

Contrary to medieval advice, a fever is not the same as overheating; it’s the body’s way of treating infectious disease. Do you grill your burgers to high temperatures to kill pathogens? So does your body. A fever is your immune system purposely frying the pants off foreign invaders that are making you ill. It’s a well-regulated function in most multicellular organisms.

That is, fevers themselves aren’t the problem. They’re the good guys—the body’s go-to defense mechanism for quashing the conditions in which bugs survive. Hyperthermia, in contrast, is an externally-caused, unregulated temperature spike that can be imminently life-threatening—like heat stroke.

Unfortunately, just about everyone, including many Western doctors, believes that fevers - even mild ones - should be treated as a threat to physical well-being. This myth may be partly an artifact of the booming over-the-counter antipyrexia industry. Fever suppression, whether by aspirin or by dutiful fasting, doesn’t do anything but trade quicker healing for momentary comfort.

When you have a fever, Moms everywhere recommend stomaching what you can to keep up your strength, and that’s extremely good advice. When it comes to regulating internal energy, your body already has you covered. There’s no need to reduce food consumption on purpose; your missing appetite already accomplishes this.

The advice to ‘starve a fever’ is the biomedical equivalent of ‘friendly fire’ and should be tossed in the dustbin of history. Does that mean you shouldn’t treat a very high fever as a medical emergency? No! A very high fever is a sign that something is dreadfully wrong and requires immediate intervention.

Why ‘Feed a Cold’?

Is ‘feed a cold’ smart advice or is it just as misleading as ‘starve a fever?’ Colds are energy-draining viruses, so it is actually helpful to keep your nutrient levels stable when you come down with a cold.

Maintaining a healthy diet keeps your immune system strong when you’re not sick. When you are ill, getting the right nutrients and sufficient energy should take center stage. Eating right is essential for helping you recover faster and making sure you don’t relapse further down the road.

Specifically, you’ll need carbohydrates for baseline glucose energy; protein to help damaged tissues heal; and of course, the mighty warriors of the immune system—antioxidant-rich vegetables. Filling up on green veggies—the greener the better—sends essential chemical signals to key immune cells, without which they wouldn’t function properly.

Eat moderately and selectively to keep your energy up. When it comes to altering food intake during illness, take it easy. Both stuffing and starving yourself are stressful actions to take against the body. If you must go overboard with some kind of intervention, try fluids. Your body can’t stay hydrated without your help.

‘Feed a cold, starve a fever,’ then, is only a half-truth. The better advice is: douse both a fever and a cold with fluids; eat if you can, especially veggies; get plenty of sleep—and let your body do the rest.