Symptom effects and central mechanism of acupuncture in patients with functional gastrointestinal disorders: a systematic review based on fMRI studies

# How Acupuncture Acts on the Gut-Brain Axis: Findings on Functional Gastrointestinal Disorders

Functional gastrointestinal disorders represent a group of conditions that affect millions of people around the world. These conditions, which include functional dyspepsia, irritable bowel syndrome, and functional constipation, are characterized by persistent digestive symptoms without structural alterations being found on conventional examinations. A recent study conducted by Chinese researchers brought new evidence on how acupuncture can benefit these patients, investigating not only the clinical effects, but also the changes that occur in the brain during treatment.

The importance of this topic lies in the fact that functional gastrointestinal disorders significantly affect patients' quality of life. Functional dyspepsia affects about 11.5% to 23.5% of the population, while irritable bowel syndrome and functional constipation have global prevalences of 11.2% and 15.3%, respectively. In addition to digestive symptoms such as abdominal pain, distension, alterations in bowel rhythm, and stool characteristics, these patients frequently develop anxiety and depression. Modern medicine recognizes that these conditions are closely related to changes in communication between the digestive system and the central nervous system, known as the gut-brain axis.

To better understand how acupuncture works in the treatment of these conditions, the researchers conducted a systematic review that analyzed ten randomized controlled clinical trials. These studies included a total of 474 participants and used advanced functional magnetic resonance imaging technology to observe the changes that occur in the brain during acupuncture treatment. The methodology included searches in five major scientific databases, with rigorous criteria for study selection. Studies were included that compared different types of acupuncture, including manual acupuncture, electroacupuncture, and transcutaneous auricular vagus nerve stimulation, with control groups receiving placebo acupuncture, medications, or other treatments.

The results demonstrated that acupuncture produced significant improvements in patients' gastrointestinal symptoms. Reduction of abdominal pain, decreased abdominal distension, improvement in stool frequency, and changes in stool characteristics were observed. Equally important was the finding that acupuncture also alleviated symptoms of anxiety and depression, confirming its beneficial effect on patients' psychological well-being. Through brain imaging, researchers identified that acupuncture promoted functional changes in specific regions of the brain, including the insula, anterior cingulate cortex, prefrontal cortex, thalamus, hippocampus, and amygdala.

These regions are fundamental for the processing of visceral sensations, pain regulation, and emotional control.

The findings about the central mechanism of acupuncture have important implications for patients and health professionals. For patients, these results offer a scientific explanation of how acupuncture can help both the digestive symptoms and the emotional aspects of their conditions. The research suggests that acupuncture does not merely relieve symptoms superficially, but acts at a deep neurologic level, restoring balance in communication between gut and brain. For practitioners, these findings provide objective evidence that can guide treatment decisions and help with the integration of acupuncture as a complementary therapy in the management of these disorders.

The study also highlighted that different acupuncture techniques can activate slightly different brain circuits, suggesting that personalization of treatment may be important to optimize results.

The study presents some important limitations that should be considered. First, all included studies were conducted in China, which may limit the generalization of results to other populations. Second, there was great variation in the acupuncture protocols used, including different acupuncture points, treatment durations, and techniques applied, making it difficult to determine which approach is most effective. Third, most studies used only resting-state brain imaging, while more advanced techniques could provide more detailed information about the mechanisms involved.

Furthermore, several studies presented methodological flaws, such as problems with treatment blinding and concealment of participant allocation, which may have influenced the results. Finally, the studies were unable to fully clarify whether the effects of acupuncture represent a true cure or only temporary symptom relief.

Despite these limitations, this research represents a significant advance in the scientific understanding of acupuncture for functional gastrointestinal disorders. The results suggest that acupuncture offers a promising approach for patients suffering from these conditions, providing both physical and psychological benefits through modulation of specific brain circuits. However, more high-quality studies are needed, with more rigorous methodologies and more diverse populations, to confirm these findings and establish more precise treatment protocols. In the meantime, patients interested in acupuncture should discuss this option with their physicians, considering it as part of an integrated treatment plan that may include other conventional therapies and lifestyle changes.