A possible mechanism underlying conditioned pain modulation

Effects of Spicy Stimulation and Spicy-Food Consumption on Human Pain Sensitivity: A Healthy Volunteer Study

Spicy-food intake has been shown to affect various human physiological systems and diseases. This study tested the analgesia effect caused by stimulation of a spicy sensation (spicy stimulation) and explored the effect of spicy-food consumption on human basal pain sensitivity. A total of 60 healthy undergraduates were included in the primary study. Placebo and sweet stimulation were used as reference interventions. Pressure and cold-pain thresholds were measured before and after taste stimulation. The frequency of spicy-food intake was also evaluated. An additional 100 subjects were recruited to validate the results. Compared to placebo stimulation, both pressure and cold-pain thresholds increased during spicy stimulation (P < .05). The increased thresholds remained, even when the taste stimulation residue was nearly eliminated (P < .05). The pressure (10.0 [2.1] vs 12.7 [3.0] kg/cm2, P < .001) and cold-pain (4.4 [1.6] vs 6.2 [2.7] seconds, P = .003) thresholds in subjects who consume spicy food ≥3 days/week were significantly lower than in those who consume it <3 days/week. In the validation population, the frequency of spicy-food intake was negatively associated with subjects' pressure (β = -.218, P = .013) and cold-pain (β = -.205, P = .035) thresholds. Spicy stimulation has an analgesia effect on adults that persists even after the taste stimulation stops. Conversely, a long-term spicy diet can reduce the human basal pain threshold. TRIAL REGISTRATION: The study protocol was approved by the Medical Ethics Committee of the Second Affiliated Hospital of Army Medical University, People's Liberation Army (identification No., 2017-023-01), and it was registered on the Chinese Clinical Trial Registry at www.chictr.org.cn (No. ChiCTR1800015053). PERSPECTIVE: This study directly examined the effects of stimulation of a spicy sensation on adult pain sensitivity and was the first to explore the relationship between long-term spicy-food intake and human pain sensitivity. The results provide evidence for future clinical pain intervention and individualized pain treatment.