Starve a Cold, Feed a Fever?

A new study finds there is truth in the folk advice to "feed a fever and starve a cold".  Researchers at Yale University looked at the effects of providing nutrients during infection. They found opposing effects depending on whether the infections were bacterial or viral. Mice with bacterial infections that were fed died, while those with viral infections who were fed lived.

"We were surprised at how profound the effects of feeding were, both positive and negative," says senior author Ruslan Medzhitov, Professor of Immunobiology and at Yale School of Medicine. "Anorexia -- not eating -- is a common behavior during sickness that is seen in people and all kinds of animals. Our findings show that it has a strong protective effect with certain infections, but not with others."

In a series of experiments, investigators infected mice with the bacterium Listeria monocytogenes, which commonly causes food poisoning. The mice stopped eating, and they eventually recovered. But when the mice were force fed, they died. The researchers then broke the food down by component and found fatal reactions when the mice were given glucose, but not when they were fed proteins or fats.

When the researchers did similar studies in mice with viral infections, they found the opposite effect. Mice infected with the flu virus A/WSN/33 survived when they were force fed glucose, but died when they were denied food or given 2-DG.

Further research showed that different areas of the brain were affected depending on which type of infection the mice died from, indicating that the animals' metabolic needs differ depending on which part of the immune system had been activated.

"Almost everything we know about infection is based on immune response studies and looking at how the immune system eliminates pathogens," Medzhitov says. "But that's not the only way we defend ourselves. There are also cases where we change and adapt so that microbes don't cause harm. Our study manipulated the ability of these mice to tolerate and survive infection without doing anything that had an effect on the pathogens themselves."