Exercise a Cold, Rest a Fever

You have probably heard the old adage, "Feed a cold, starve a fever." There is something to the advice. When you eat, your body has to burn the calories. The burning of food creates carbon dioxide, and you breathe more deeply to take in oxygen in and breathe the carbon dioxide out. Deeper breathing loosens up phlegm and helps you get over a cold faster.

Eating a few extra fats and sugars increases your body's production of inflammatory chemicals. That is usually not a good thing. You don't want inflammation in your joints or in your arteries. But when you have a viral infection of the respiratory tract, inflammation can help your body get rid of infected cells and to create the mucus and phlegm that isolate viruses so you can expectorate the infection out of your system.

One time it is important not to feed your cold is when you are taking high-dose vitamin C. That is because eating more increases the acidity of the mucus lining your upper respiratory tract, and vitamin C works best in an alkaline environment. But it's only the first dose of vitamin C that helps you get over your symptoms.

While feeding a cold helps you open up, stoking your calorie-burning metabolic furnace is not a good idea when you have a fever. Your body turns up its thermostat to kill viruses. Adding heat to your fever doesn't make the viruses any more dead. It just makes you more uncomfortable.

The same thing can be said for moderate exercise, which also gets you sweaty and warmer. Anything that makes you breathe a little faster and a little more deeply helps loosen phlegm. Anything that makes you hot and sweaty puts more stress on your immune system and can cause a setback. But there is a simple, commonsense rule that can help you know whether exercise would be beneficial or not.