Pre-operative modification of dietary glycemic index improves pre but not post-operative indices of insulin resistance in patients undergoing coronary artery bypass graft surgery

Background: Improving insulin sensitivity in coronary artery bypass grafting (CABG) patients may translate into improved glycemic control and postoperative outcomes. The implementation of a low glycemic index (LGI) diet in the pre-operative period may improve insulin sensitivity and subsequently impact on the development of post-operative insulin resistance. The aim of this study was to determine whether a short term LGI diet would reduce postoperative insulin resistance. Methods: Eleven non-diabetic patients referred for elective CABG surgery were randomized to consume either a high glycemic index (HGI)(5) or LGI (6) diet for three weeks prior to their surgery. Outcomes, including insulin sensitivity (SITT, HOMA), were measured at baseline, preoperatively and postoperatively. Results: Substitution of HGI or LGI foods resulted in an average 8.6 unit increase, or 11.0 unit decrease, respectively, in glycemic index. Insulin sensitivity (HOMA) improved significantly in the LGI group preoperatively compared to the HGI group (p = 0.018). Insulin sensitivity (SITT) was significantly reduced postoperatively in both groups, but no significant difference was found between groups. There was a trend in the LGI group towards improved glycemic control which warrants further investigation. Conclusion: A preoperative LGI diet presents a non-invasive cardio-protective opportunity warranting clinical trial.