Dietary cod protein improves insulin sensitivity in insulin-resistant men and women: a randomized controlled trial.

Abstract

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. 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). Beta-cell function, estimated by oral glucose tolerance test-derived parameters, was also assessed. There was a significant improvement in insulin sensitivity (P = 0.027) and a strong tendency for a better disposition index (beta-cell function x 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 x 10(-3) mg x kg(-1) x min(-1) x pmol(-1)) was taken into account, an interaction on the 30-min C-peptide-to-30-min glucose ratio, used as an index of beta-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). 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.