“I have no strength, I am always tired, I am dying of sleep. I sleep a lot but wake up without energy. In addition, I suffer from pain in many areas of the body and if I make an extra effort, I pay for it later. My memory fails me a lot and I have a hard time concentrating on things. Everything exhausts me; I'm sick of living like this."
This is the real testimony of a patient with chronic fatigue, a problem suffered by between 2 and 6% of the population in developed countries and some 900,000 people in Spain. In her case, she appeared after a SARS-CoV-2 infection.
Although the cause is not yet clear, it affects people diagnosed with fibromyalgia and many patients with a post-covid condition, the official definition of the World Health Organization for what is also known as persistent covid.
For a long time, some health professionals have doubted its existence —and even continue to do so today— due to the lack of biomarkers to diagnose it. This makes their treatment much more difficult and patients do not understand what is happening to them either.
However, chronic fatigue syndrome has already been known for years. It is detected when the symptoms last more than six months (even years) and do not improve with rest. Apart from tiredness, it is usually accompanied by symptoms such as mental fog, discomfort after making an effort, headaches, muscle or joint pain, and low mood.
The appearance of cognitive and emotional alterations may have influenced the belief that it is an exclusively psychological problem, but this is not the case: on a physiological level, chronic fatigue is related to an increase in pro-inflammatory substances in the body due to an exaggerated activation of our defensive system.
In recent times, researchers have also linked this disease with an alteration of the intestinal microbiota, the ecosystem of microorganisms that live in our intestine. They feed on what we eat and in return generate useful and necessary substances for us. And as we will see below, its imbalance could explain the cognitive and emotional symptoms that characterize chronic fatigue.
When the body presents high levels of inflammation, pro-inflammatory substances have the ability to reach the brain and modify the action of microglia, cells that collaborate with neurons. This can start a cascade of inflammatory changes in the brain.
But this organ has no pain receptors. It does not hurt. Therefore, inflammation manifests itself differently: with mental fog, slowing down of thought, tiredness, depression, drowsiness, fatigue, lack of motivation, etc. That is, symptoms very similar to those reported by patients with chronic fatigue syndrome with high levels of inflammation.
Although the mechanisms are still not entirely clear, changes in the microbiota could affect the immune system, which would "neuroinflamm" the brain. So it is very possible that the aforementioned mental symptoms are related to what happens in the intestine, as more and more scientists point out.
Thus, a study carried out at Cornell University (New York) showed that people with chronic fatigue not only had a reduced and altered microbiota, but also had increased intestinal permeability. This hypermeability may be related to inflammation in patients.
For its part, a 2022 investigation found that the proliferation of certain bacteria in the small intestine can also trigger cognitive alterations.
All this reinforces the idea of the involvement of the gut-brain axis and the action of neuroinflammation. In fact, other research concluded that the gut and lung microbiome play a fundamental role in the development and treatment of the post-covid condition.
It is also true that a 2018 systematic review was unable to establish any relationship between the microbiota and chronic fatigue. This is explained because many investigations had not assessed the large number of drugs that those affected take, capable of altering the community of microorganisms that inhabit our intestine.
But that same year, a study published in the journal Frontiers in Microbiology refuted it, linking two types of microorganisms – from the genera Paraprevotella and Ruminococcaceae UCG_014 – with the risk of appearing to be chronic fatigue syndrome.
To this we must add another 2018 work published in Cell Host magazine
These changes in the microbiota may be due to the intake of medications, food or having suffered an infection from certain viruses or bacteria.
It is true that each person has their own community of microorganisms and that they must be analyzed individually, but there are certain probiotics –such as those rich in Bifidobacteria infantis strain 35624– that seem to reduce inflammation.
Lifestyle also influences. Practicing outdoor activities, reducing stress, respecting sleep-wake cycles or reducing the consumption of antibiotics and antacids help keep our microbiota healthy.
And in terms of food, it is usually recommended to reduce the consumption of ultra-processed foods, sugars and gluten and increase the consumption of fruits, vegetables and oily fish (rich in omega-3).
It seems that a field of study is opening up with possible solutions, but also with many doubts pending to be resolved.
This article was originally published on The Conversation. Beatriz Carpallo Porcar is
professor in the degrees of Physiotherapy and Nursing at the Universidad San Jorge. Researcher on the Post Covid Condition at the Aragon Health Research Institute, San Jorge University.
