Dietary Cod Protein Improves Insulin Sensitivity in Insulin-Resistant Men and Women

Abstract

OBJECTIVE—The purpose of this article was to compare the effects of cod protein to those of other animal proteins on insulin sensitivity in insulin-resistant human subjects. RESEARCH DESIGN AND METHODS—Insulin sensitivity (M/I) was assessed using a hyperinsulinemic-euglycemic clamp in 19 insulin-resistant subjects fed a cod protein diet and a similar diet containing lean beef, pork, veal, eggs, milk, and milk products (BPVEM) for 4 weeks in a crossover design study. Both diets were formulated to differ only in protein source, thus providing equivalent amounts of dietary fibers and monounsaturated, polyunsaturated (including n-3), and saturated fatty acids (1.1:1.8:1.0). β-Cell function, estimated by oral glucose tolerance test–derived parameters, was also assessed. RESULTS—There was a significant improvement in insulin sensitivity (P = 0.027) and a strong tendency for a better disposition index (β-cell function × M/I) (P = 0.055) in subjects consuming the cod protein diet compared with those consuming the BPVEM diet. When median baseline M/I (4.8 × 10−3 mg · kg−1 · min−1 · pmol−1) was taken into account, an interaction on the 30-min C-peptide–to–30-min glucose ratio, used as an index of β-cell function, was observed between diet and M/I status (P = 0.022). Indeed, this ratio strongly tended to increase in subjects with low M/I consuming the cod protein diet compared with those consuming the BPVEM diet (P = 0.065). CONCLUSIONS—Dietary cod protein improves insulin sensitivity in insulin-resistant individuals and thus could contribute to prevention of type 2 diabetes by reducing the metabolic complications related to insulin resistance.