Scheduling days without food may have a knock-on effect that eases both chronic pain and its associated cognitive problems, according to a study on mice by researchers from the First Affiliated Hospital of Zhengzhou University in China.
The findings build on a growing body of research on the neurological connections between the brain and the digestive system, emphasizing the importance of our gut bacteria in maintaining good cognitive health.
Chronic pain is more than just a persistent state of discomfort that affects millions around the globe. The condition also puts individuals at risk of poor mental health, typically in the form of anxiety and depression. Yet current treatments treat the two states as separate conditions, targeting either the cognitive disorders or the pain.
Curiously, chronic pain and its associated impact on our mental functioning both appear to be strongly linked with the brain-gut axis. This could be a consequence of a breakdown in the functioning of the nerves themselves, hormonal dysregulation, changes in our gut’s microbes, or a combination of factors.
While research suggests intermittently abstaining from eating a significant number of calories may have an analgesic effect through hormone signalling, promoting repair of neural insulation, and reducing inflammation in the brain, there is little evidence of its impact on the mental health side of chronic pain.
To better understand the full relationship between each factor, researchers turned to mice engineered to have one of several different types of long-term discomfort, such as a constrictive injury or pain from inflammation.
Over 38 days, a selection of adult male mice alternated days of feeding with days without access to food. The rest of the mice were permitted to eat throughout the experiment.
Each animal then underwent a battery of tests to study their pain sensitivity, anxiety-like symptoms, gut microbes, metabolites, and neuroinflammation.
Responses to pain, such as heat, dropped throughout the different mouse models that underwent periodic fasting, as did cognitive deficits. Fasting mice with ongoing pain from a constrictive injury showed a drop in anxiety-like behavior, compared with controls.
Fasting mice also presented signs of a stronger gut barrier and reduced inflammation of the nervous system. The makeup of their gut’s microflora had also changed, with a species of bacteria called Alistipes finegoldii increasing significantly in numbers.
By topping up the guts of non-fasting mice with the bacteria, the researchers found they could reproduce many of the analgesic and mind-healing effects of intermittent fasting.
Further analysis suggests a compound called hippuric acid could be a key step in the therapeutic pathway. Produced when gut bacteria break apart specific nutrients in food, the metabolite was found to trigger a specific neuroimmune pathway known as the Stimulator of Interferon Genes, or STING.
Drawing a clear line that connects fasting with neuroinflammation through a common gut microbe and its impact on our blood’s chemistry provides researchers with a map they can explore for treating chronic pain and its associated mental anguish.
None of this means intermittent fasting is a cure for ongoing pain and anxiety, of course. More research is needed to reveal the full picture of the so-called Alistipes finegoldii–hippuric acid–STING neuroimmune axis.
However, there are multiple benefits to fasting as a part of a controlled, medically responsible diet. One day, the management of chronic pain and its cognitive impacts may be one of them.
This research was published in Brain, Behavior, and Immunity.
Source: MedicalXpress
