Introduction: Attention Deficit Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental condition marked by symptoms of inattention, impulsivity, and hyperactivity. While its exact causes remain unclear, genetic, environmental, and neurobiological factors are implicated. Emerging research on the microbiota-gut-brain axis (MGBA) highlights the significant influence of gut microbiota on brain function and behavior, suggesting a novel avenue for ADHD intervention. Dietary components can alter gut microbial composition, presenting opportunities for targeted modulation through nutrition. Chili peppers, rich in bioactive compounds such as capsaicin, vitamin C, and fatty acids, have demonstrated effects on both the central nervous system and gut microbiota. Capsaicin, in particular, has shown promise in neurological disorders like Parkinson’s disease and depression. These findings suggest that chili peppers may hold therapeutic potential for ADHD by modulating gut microbiota, although further rigorous studies are needed to confirm these effects and clarify underlying mechanisms.
Methods: This review comprehensively examined peer-reviewed cohort, case-control, and interventional studies published between 2019 and 2025, retrieved through systematic keyword searches across databases including PubMed, Scopus, Medline, and ScienceDirect. Selection criteria prioritized research focused on the effects of capsaicin and chili-derived bioactive compounds on gut microbiota composition, neuroinflammation, neurotransmitter modulation (particularly dopamine and serotonin), and behavioral outcomes relevant to ADHD. Both preclinical and clinical studies were included to explore mechanistic pathways underlying the gut–brain axis, with specific attention to dietary modulation, microbiota diversity, and neurochemical signaling.
Results: Dietary interventions, including the Mediterranean diet, ketogenic diet, and elimination diets, demonstrate significant improvements in ADHD symptoms by modulating gut microbiota composition and function. Key bioactive compounds in chili peppers—capsaicin (CAP), vitamin C, and omega-3 polyunsaturated fatty acids—exert beneficial effects on ADHD through gut microbiota regulation. CAP influences the gut-brain axis by activating TRPV1 receptors, altering microbial diversity, and enhancing neurotransmitter production. Vitamin C promotes the growth of beneficial bacteria such as Lachnospiraceae and increases short-chain fatty acid (SCFA) production, contributing to anti-inflammatory and antioxidant effects. Omega-3 PUFAs improve cognitive function by restoring microbial balance and increasing SCFA-producing bacteria. Collectively, these dietary components modulate neuroimmune, neuroendocrine, and neural pathways via the microbiota-gut-brain axis, reducing neuroinflammation and improving neurotransmitter synthesis, thereby alleviating core ADHD symptoms.
Conclusion: Dietary modulation of the gut microbiota presents a promising complementary approach for managing ADHD, with chili peppers offering potential therapeutic benefits due to their active compounds—capsaicin, vitamin C, and omega-3 fatty acids. These components influence the microbiota-gut-brain axis through anti-inflammatory, antioxidant, and neuroprotective mechanisms. While current findings, mainly from animal and in vitro studies, suggest positive effects, robust clinical evidence in human populations is still lacking. Future research should focus on well-designed, large-scale clinical trials to determine safe dosage ranges, long-term effects, and individual responses, paving the way for the development of personalized dietary interventions and novel therapeutic strategies for ADHD.
Keywords: ADHD, gut microbiota, capsaicin, dietary intervention