An examination of the effects of isoenergetic intragastric infusions of pure macronutrients on cold pain perception in healthy human volunteers.

Our previous study demonstrated that meals, particularly when rich in fat, significantly reduced the pain induced by the cold pressor stimulus in healthy human subjects. To determine the mechanisms involved, the aim of this study was to bypass the taste and cognitive component of food and to investigate the scope of these analgesic effects with direct intragastric infusion of pure macronutrients in a group of 16 healthy human volunteers (eight male and eight female) on the response to cold-induced pain. All subjects underwent the cold pressor test (CPT) on three occasions in a counterbalanced order: before and after intragastric intubation and infusion of isoenergetic fat (10% intralipid), carbohydrate (CHO-maltodextrin), and a control infusion of isotonic saline. All solutions were of equal volume and administered at room temperature. The CPT was carried out four times on each test day, once before intubation, and 0.5, 1.5, and 2.5 h after intragastric infusion. Radial pulse and blood pressure measurements and visual analogue scales of mood/emotional state were carried out before and after each CPT. There were no significant differences in pain scores between the three test conditions, suggesting that by bypassing the cognitive and taste component of eating, the trigger for any postingestive analgesic effects of food are lost.

The influence of food on pain perception in healthy human volunteers.

The aim of this study was to investigate if food could reduce pain perception in a group of 16 healthy human volunteers (8 male and 8 female), and to explore the differential effects of macronutrient composition on the response to cold-induced pain. All subjects underwent the cold pressor test (CPT) on 3 occasions in a counterbalanced order, before and after administration of isoenergetic high-fat low-carbohydrate (CHO) and high-CHO low-fat meals, and when no meal was given. The CPT was carried out 4 times on each test day, once before the meal, and 0.5, 1.5, and 2.5 h after the meal, and at the equivalent times on the day when no food was given. Radial pulse and blood pressure measurements and visual analogue scales of mood/emotional state were carried out before and after each CPT. Mean pain scores were significantly reduced following both meals compared with the no-food condition. The maximum reduction in pain occurred 1.5 h after ingestion, and a significantly greater effect was exerted by the high-fat low-CHO meal compared with the high-CHO low-fat meal. These results demonstrate that food, particularly when rich in fat, significantly reduces the pain induced by the cold pressor stimulus in healthy human subjects.