When we have a cold or a fever, our eating habits change. Often we may lose our appetite and eat very little food.

However, a recent study suggests that we should treat fever and cold differently, because our body immune system has different responses to the two types of infections. The finding is recently published in Cell.

Usually, colds are caused by viruses, and fevers are caused by bacterial infection. In both cases, inflammation occurs because an invader is detected by the immune system. To survive an infection, we need to tolerate our own immune responses when the immune system is killing the invaders.

In the study, researchers found that the fasting metabolism of the body treats bacterial and viral infections differently: it is protective in bacterial infection but not in viral infection.

Researchers conducted experiments on mice with a cold or fever. When mice have these illnesses, they are just like humans, losing their appetite in the beginning. But it is observed that mice with cold resumed eating, whereas mice with fever stopped eating.

It is possible that eating is helpful to survive the viral infection (colds), but harmful to survive the bacterial infection (fevers). Researchers tested this possibility by changing metabolic processes in mice.

They found that when mice had a viral infection, they needed glucose (a type of sugar providing energy) to protect their brain cells from being hurt by the inflammation.

On the other hand, when the mice had a bacterial infection, they dealt with the illness better if there was a lack of sugar. It is known that the body will metabolize fat when there is no sugar. This process generates chemicals called ketones that can benefit the body with bacterial infection.

The finding suggests that when we have a cold, it may be more helpful if we have food rich in carbohydrates (and hence glucose), e.g., chicken soup. But when we have a fever, it may be better to avoid food rich in carbohydrates.

Researchers suggest that this study can help develop new diagnosis methods and new ways to fight against colds/flus and fevers in the near future.

Citation: Wang A, et al. (2016). Opposing Effects of Fasting Metabolism on Tissue Tolerance in Bacterial and Viral Inflammation. Cell, 166: 1512-1525.e12. doi: 10.1016/j.cell.2016.07.026

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