Consumption of a Legume-Enriched, Low-Glycemic Index Diet Is Associated with Biomarkers of Insulin Resistance and Inflammation among Men at Risk for Colorectal Cancer

Abstract

The Legume Inflammation Feeding Experiment is, to our knowledge, the first randomized crossover feeding trial testing the effects of a legume-enriched, low-glycemic index (GI) diet among men characterized for colorectal adenomas and insulin resistance (IR) status. This study was designed to test the effects of a legume-enriched diet compared with a healthy American (HA) diet under weight-stable conditions. The primary objective was to assess effects on C-reactive protein (CRP) and C-peptide levels. The secondary objective was to assess changes by IR status or history of adenomas. A total of 64 men who completed a colonoscopy within the previous 2 y consumed 2 diets in random order each for 4 wk separated by a washout period. The diets were a legume-enriched (250 g/d), low-GI (GI 38) diet and a high-GI (GI 69) HA diet. We measured fasting glucose, insulin, C-peptide, CRP, and soluble tumor necrosis factor-α receptors I and II (sTNFRI/II) at the beginning and end of the diet periods. Participants who consumed both the legume and HA diets had favorably improved CRP (−20.2 and −18.3%) and sTNFRI (−3.7 and −4.4%) concentrations, respectively. The sTNFRII concentrations declined marginally during the legume diet period (−3.8%; P = 0.060) and significantly during the HA diet period (−5.1%; P < 0.001). Fasting glucose increased significantly during both the legume (+1.8%) and HA (−2.2%) diet periods. Only the changes in glucose differed between the diet periods. Serum C-peptide and plasma insulin levels did not change in participants consuming either diet. Healthful dietary changes can improve biomarkers of IR and inflammation.