Feed a cold – Starve a fever?

Have you ever noticed that when your puppy or cat gets sick, they tend to stop eating for a while? Well, feed a cold-starve a fever is an old saying, but does it really hold water?  According to a new study there might be some truth in this, according to what researchers found with mice.  The mice with a bacterial infection died after being fed, while mice with a viral infection survived after eating.  Ruslan Medzhitov, senior author and a Howard Hughes Medical Institute investigator at Yale School of Medicine in New Haven, Ct and team, have reported their findings in the journal Cell.  He reports that most of their knowledge about bacterial and viral infections stems from studies that have investigated how the immune system responds to pathogens and how it works to eradicate them.

Other ways to defend ourselves is where we change and adapt, so that microbes don’t cause harm.  The team found in the latest study that food intake during infection may influence the immune system’s ability to fight pathogens, depending on whether the infection is bacterial or viral, and what type of foods are consumed.  The effects of feeding were both positive and negative, but show it has a strong protective effect with certain infection, but not with others. These findings were conducted through a series of mouse experiments in which they fed or starved mice that had been infected with bacteria or viruses.

The team first infected mice with Listeria monocytogenes, which is a bacterium know to cause food poisoning.  The mice stopped eating just as expected, which is a common occurrence with food poisoning.  They did eventually make a full recovery, but those infected with L. monocytogenes that were force-fed, died.

The team also found that it was glucose that proved fatal to the force-fed mice, and proteins and fats appeared to have no effect.  When the chemical 2-DG was administered (inhibits glucose metabolism) to force-fed infected mice, the glucose no longer proved fatal.  The mice were also infected with the flu virus A/WSN/33 in another experiment.  The team found that force-feeding these mice with glucose led to their survival, but those given 2-DG, or starved of glucose, died.

The team found by analyzing the brain scans of the mice that died from either bacterial or viral infection, that each infection affected different brain regions.  This suggests that the metabolic requirements of the mice may be determined by what parts of their immune system are switched on.  

Findings could be beneficial for sepsis research.  The team believes their current findings may have important implications of research into this potentially fatal blood infection.  Sepsis is a critical problem faced by hospital ICUs that defies most modern medical approaches.  They are now in the process of seeing how changes in sleep patterns might affect the immune system’s ability to stave off infection.  Studies are also being conducted that will investigate what pathways play a role in food preferences, in an attempt to explain certain food cravings people have when they are ill.  

Some studies are looking at nutrition in those patients with sepsis, and results have been mixed.  The studies do not segregate patients based on whether their sepsis was bacterial or viral.  Trials should be designed on the premises that patients should be stratified by the cause of their sepsis.

-Dr Fredda Branyon