The immune system supports healthy bodies, too

The immune system is a complex network of cells and proteins that are found all throughout the body. While it is well known that the immune system helps to defend the body against infection, a new study reveals that immune cells are also hard at work when the body is perfectly healthy. 

Study co-lead author Anne Loft is a postdoc at the Department of Biochemistry and Molecular Biology at the University of Southern Denmark.

“Until recently, it was believed that the immune system was mostly dormant unless the body was under attack in connection with infections. However, it now turns out that the immune system most likely also plays an important role for perfectly healthy people and can affect the body’s production of vital energy sources,” said Loft.

The experts found that in a healthy body, the immune system causes the liver to produce an energy source called ketone bodies during the metabolism of fats. 

“When we’re fasting – that is, we haven’t eaten anything for maybe half a day or a full day – we start drawing on our fat deposits, but not all of our body cells are capable of burning fat. This applies, among other things, to the brain, which instead depends on the production of ketone bodies, which the liver forms by metabolizing fats,” explained study co-lead author Søren Fisker Schmidt. “The ketone bodies thereby energize the body, allowing us to function even if we don’t eat anything.”

Ketone bodies are the focus of many popular weight loss strategies that aim to cut out carbohydrates. In the absence of carbs (and glucose), the body begins to burn stored fat. Beyond promoting weight loss, ketone bodies have been linked to improve levels heart health and blood sugar levels. 

“We now believe that the immune system affects the production of ketone bodies in fit and healthy individuals and given the beneficial effects of ketone bodies in various common metabolic disorders, this knowledge can hopefully also be applied to understand how the immune system is trying to keep the body in equilibrium when we’re sick,” said Loft.

The study is published in the journal Cell Metabolism. 

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By Chrissy Sexton, Earth.com Staff Writer