Post-prandial cardiovascular responses in man after ingestion of carbohydrate, protein or fat.

Changes in cardiac output and in superior mesenteric arterial flow were followed with Doppler ultrasound techniques in five young, healthy persons for 2 h after ingestion of medium-sized (4 MJ), fluid meals containing either carbohydrate, protein, fat or water only. Measurements were carried out before meals and at regular post-meal intervals, during which mean arterial blood pressure was also followed. All energy-containing meals caused marked and gradually developing post-prandial increases in cardiac output as well as in superior mesenteric arterial flow. The maximum flow levels were reached in the course of 30-60 min and maintained until the observations ended after 2 h. The intake of water caused no such flow increases. There were considerable interpersonal variations in the size and in the speed of development of the flow increases after the three types of energy-containing meals. The flow-increasing effects of the three meal types were not significantly different, even if the most marked increases (median values about 11 min-1 for both cardiac output and superior mesenteric arterial flow) occurred after carbohydrate meals. The marked effects on circulation of the three food components were also revealed in the calculated, integrated amounts of 'extra' cardiac output and superior mesenteric arterial flow observed in the course of the 2 h following the meal. Values of more than 100 1 for such 'extra' flows were seen after carbohydrate meals. The marked ingestion-released increase in blood flow to the splanchnic organs is apparently partly met by an increase in cardiac output, and partly by some redistribution of flow, which benefits the digestive system.