The desire to eat during illness is tied to whether the body requires glucose energy to fight off the infection, say researchers at Harvard University. Photo by Michal Kowalski/Shutterstock
NEW HAVEN, Conn., Sept. 22 (UPI) -- While some people prefer to eat while sick and others can't stand the sight of food, a new study suggests the desire to eat during an infection has more to do with the infection itself than the infected person.
Eating helps the body defeat viral infections, but eating certain foods can hinder its ability to fight a bacterial infection, say researchers at Harvard University, who found the difference is in whether the body requires glucose to fight the infection.
The researchers say the instinct for whether or not to eat during sickness has evolved over millions of years to match exactly what cells need for survival, and gaining a greater understanding of how this works could help doctors treat infections more effectively.
"When animals are infected they stop eating and they switch to a fasting metabolic mode," Ruslan Medzhitov, an immunobiologist at Harvard University, said in a press release. "The question was whether fasting metabolism is protective or detrimental."
For the study, published in the journal Cell, researchers fed groups of mice with either viral or bacterial infections to see the effects of food consumption on the illness.
Mice with viral infections survived their illness after being fed, but those with bacterial infections died from their illness. Nutrient tests on the animals for fat, protein and glucose showed glucose caused detrimental effects on those with bacterial infections.
The researchers repeated the experiment, feeding both groups of mice again, but blocked glucose metabolism in both sets of rodents. This time, mice with bacterial infections survived and those with virus infections died.
Based on the results, the researchers surmise each infection causes a different type of inflammation and the immune response and tolerance of inflammation was affected by types of nutrition. The theory, Medzhitov said, is the production of ketones -- used by cells for energy in the absence of glucose -- when sick people don't eat is needed to survive a bacterial infection.
The study suggests dietary preferences of sick people are more than just preferences and, though more research is needed to understand how this works, the researchers say the new knowledge could help doctors decide when, how and what to feed ill patients.