Capsaicin—the spicy ingredient of chili peppers: A review of the gastrointestinal effects and mechanisms

Chili peppers are commonly consumed spices worldwide and capsaicin is the main source for the spicy flavors, which is reported to have many biological activities. However, long-time consumption of chili peppers may probably cause the gastrointestinal discomfort due to the strong pungency of capsaicin. The beneficial and adverse effects of capsaicin on gastrointestinal health and the underlying mechanisms haven't been revealed. The review summarized the effects of capsaicin ingestion on the gastrointestinal tract and their possible mechanisms, illustrated the current and potential strategies for relieving capsaicin-induced discomfort, and provided insight into further studies on capsaicin and gastrointestinal health. Key Findings and Conclusions: Long-term and high levels of capsaicin ingestion may cause gastrointestinal discomfort and affect gastrointestinal digestion, which is more pronounced in specific gastrointestinal disorders. By analyzing the possible mechanisms, we found that capsaicin receptor TRPV1 and the neuropeptides can regulate the visceral pain and immune response, thereby affecting the oxidative stress and tissue permeability of the gastrointestinal tract. Furthermore, capsaicin can alter the structure of gut microbiota and affect the levels of short chain fatty acids (SCFAs). Current strategies can only decrease the oral pungent taste, but cannot relieve the gastrointestinal discomfort. Based on the effects of probiotics on gastrointestinal disorders and the correlation studies between probiotics and TRPV1, probiotics have the potential to relieve the capsaicin-induced gastrointestinal discomfort.