Can chili peppers improve ADHD symptoms? Scientists explore their gut-brain connection

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Feb 20 2025

Scientists uncover how chili peppers may influence ADHD symptoms through gut-brain connections—could diet play a bigger role in treatment?

Research: The possible effects of chili peppers on ADHD in relation to the gut microbiota. Image Credit: MarcoFood / Shutterstock

In a recent review article in the journal Frontiers in Nutrition, researchers described what is currently known about the potential application of chili peppers in treating attention deficit hyperactivity disorder (ADHD) through its impacts on the gut microbiome.

Capsaicin, the active component found in peppers, along with fatty acids and vitamin C, may modify gut microbial communities and improve ADHD symptoms through the gut-brain axis. Research suggests capsaicin can influence neurotransmitter levels, including serotonin and dopamine, and reduce oxidative stress and neuroinflammation—factors implicated in ADHD pathology. However, research in this field remains preliminary. Rigorous trials are necessary before these properties can be established.

ADHD and Quality of Life

A common neurodevelopmental disorder in children is ADHD, characterized by impulsive behavior, attention deficits, and excessive activity.

Many children with ADHD continue to struggle with the condition as adults, while many adults remain undiagnosed. This condition severely affects interpersonal relationships and academic performance, and adults with ADHD suffer higher levels of daytime sleepiness, depression, and anxiety.

What causes ADHD development remains poorly understood, but psychosocial factors, atypical brain development, environmental influences, and genetic predisposition all play their part. Recent studies also suggest that the gut microbiota may contribute to ADHD by influencing neurotransmitter production and brain structure.

Doctors often prescribe drugs such as atomoxetine and methylphenidate to treat symptoms, but these medications have side effects such as insomnia, mood instability, loss of appetite, nausea, and vomiting.

Research into new therapies can lead to safer and more effective alternatives.

Diet, Gut Microbiota, and the Gut-Brain Axis

The gut microbiome, a microbial ecosystem found in mammalian gastrointestinal tracts, is a complex, dynamic system that significantly contributes to human health. It is critical for digestion, immunity, and heart and brain health.

Dietary patterns affect the metabolic activity and composition of gut microbes. Research shows a bidirectional relationship between the gut and brain, often termed the microbiome-gut-brain axis (MGBA), in which diet plays a critical role.

Diets rich in dietary fiber and healthy bacteria increase diversity, short-chain fatty acid (SCFA) production, and the development of bioactive compounds that improve brain function, gastrointestinal health, and metabolic health.

The Mediterranean diet, for example, increases beneficial bacteria populations such as those of Roseburia species and Faecalibacterium prausnitzii. However, diets rich in processed foods have been linked to depleted gut microbiomes and psychiatric, metabolic, and gastrointestinal disorders.

Through the MGBA mechanism, researchers believe the gut microbiome affects the development of diseases such as epilepsy, autism, Alzheimer’s disease, and ADHD. Recent animal studies show that transplanting gut microbes from ADHD patients into mice led to structural changes in the brain’s white and gray matter, supporting the idea that gut microbiota plays a causal role in ADHD symptoms.

Individuals with ADHD have less Lactobacillus in their gut microbes, and lower diversity appears to be correlated with higher hyperactivity.

In addition, some gut bacteria regulate neurotransmitter production, including dopamine and serotonin, which are critical for attention and mood regulation in ADHD.

When scientists transferred gut microbes from people with ADHD to mice, they found that it reduced the brain's structural integrity of grey and white matter.

Moreover, mice with these modified gut microbiomes changed their behavior. These experiments have led scientists to explore dietary interventions and nutritional supplementation as treatment options for ADHD.

Chili Peppers and ADHD

Peppers contain bioactive compounds such as fatty acids, vitamin C, and capsaicin. Chili peppers are increasingly produced and consumed worldwide and are integral to many dishes. They have also been shown to have anti-inflammatory, antioxidant, and lipid-reducing effects, and their bioactive compounds can modify the gut microbiome.

Capsaicin, which contributes to peppers' pungent taste, can move through the blood-brain barrier and act directly on the nervous system through transient receptor potential vanilloid 1 (TRPV1), which is found in the hippocampus, striatum, and cerebral cortex. These brain regions are critical for attention, impulse control, and emotional regulation—functions impaired in ADHD.

Capsaicin can also regulate synaptic plasticity and transmission, cognitive function, and autophagy. These properties make it important for protecting against cancer, hypertension, obesity, stroke, depression, and cardiovascular disease while alleviating cognitive impairment and pain, preventing neurodegenerative conditions, and reducing oxidative stress.

There is also evidence that it can affect gut microbes' function, abundance, and composition. Studies suggest capsaicin may enhance the ratio of beneficial gut bacteria like Firmicutes to Bacteroidetes, increase serotonin availability, and reduce gut inflammation, all of which may impact ADHD symptoms.

These links suggest that capsaicin could be helpful for people with ADHD.

In addition to capsaicin, chili peppers contain significant amounts of vitamin C, an estimated 43-247mg in 100g of fresh fruit. As a free radical scavenger and antioxidant, it promotes the absorption of iron ions, regulates the function of the immune system, and participates in the synthesis of hormones, carnitine, and collagen.

Research indicates that vitamin C supplementation can increase beneficial gut bacteria like Lachnospiraceae, which are known to support gut health and reduce inflammation. This suggests that vitamin C could have similar effects in those with ADHD.

The third important bioactive in chili peppers is polyunsaturated fatty acids (PUFAs), including omega-3 and omega-6 fatty acids.

There is evidence that people with autism, depression, and ADHD have omega-3 PUFA deficiencies and that supplementation can improve memory function for children with ADHD and increase bacteria that produce SCFAs in the gut.

Potential Risks and Limitations

This review outlines hypothetical pathways through which chili peppers, due to their bioactive compounds (vitamin C, fatty acids, and capsaicin), could regulate the gut microbiome and thus improve neural, endocrinal, immune, and ADHD pathways.

Rigorous clinical trials can explore these mechanisms and may result in effective treatments that do not come with the adverse effects of existing ADHD medications.

However, the researchers caution that there is currently no direct clinical evidence that chili peppers can effectively treat ADHD. Most of the findings come from animal or in vitro studies, and human trials are necessary to confirm these effects.

Additionally, excessive capsaicin intake may cause gastric irritation, neurotoxicity, or other adverse effects. Future research will need to determine safe and effective dosages for therapeutic use.

Conclusion

While chili peppers contain bioactive compounds that may influence the gut-brain axis and contribute to ADHD symptom management, their effects remain speculative until more rigorous human studies are conducted.

As an easily accessible dietary component, peppers could provide a potential adjunct therapy, but they should not be considered a replacement for established ADHD treatments.