Comprehensive assessment of the global and regional vascular responses to food ingestion in humans using novel rapid MRI

Ingestion of food is known to increase mesenteric blood flow. It is not clear whether this increased flow demand is compensated by a rise in cardiac output (CO) alone or by redistribution of blood flow from other organs. We used a new comprehensive imaging method to assess the human cardiovascular response to food ingestion. Following a 12-h fast, blood flow in segments of the aorta and in organ-specific arteries, and ventricular volumes were assessed in 20 healthy adults using MRI at rest and following ingestion of a high-energy liquid meal. Systemic vascular resistance (SVR) fell substantially and CO rose significantly. Blood pressure remained stable. These changes were predominantly driven by a rapid fall in mesenteric vascular resistance, resulting in over four times more intestinal blood flow. Renal vascular resistance also declined but less dramatically. No changes in blood flow to the celiac territory, the brain, or the limbs were observed. In conclusion, this is the first study to fully characterize systemic and regional changes in vascular resistance after food ingestion in humans. Our findings show that the postprandial drop in SVR is fully compensated for by increased CO and not by redistribution of blood from other organs. With the exception of a modest increase in renal blood flow, there was no evidence of altered blood flow to nondigestive organs. The proposed oral food challenge protocol can be applied safely in an MRI environment and may be useful for studying the involvement of the gut in systemic or cardiovascular disease.