Glycemic Index versus Wheat Fiber on Arterial Wall Damage in Diabetes: a randomized controlled trial

Abstract

<p> </p> <p><strong>OBJECTIVE: </strong>High cereal fiber and low glycemic index (GI) diets are associated with reduced cardiovascular disease (CVD) risk in cohort studies. Clinical trial evidence on event incidence is lacking. Therefore, to make trial outcomes more directly relevant to CVD we compared the effect on carotid plaque development in diabetes of a low GI diet versus a whole grain wheat fiber diet. </p> <p><strong>RESEARCH DESIGN AND METHODS: </strong>169 men and women with well controlled type 2 diabetes were randomized to counseling on either low GI or whole grain wheat fiber diets for 3 years. Change in carotid vessel wall volume (VWV) (pre-specified primary endpoint) was assessed by magnetic resonance imaging as an indication of arterial damage. </p> <p><strong>RESULTS: </strong>134 of 169 randomized participants completed the study. No treatment differences were seen in VWV. However, on the whole grain wheat fiber diet, VWV increased significantly from baseline, 23 mm3 (95% CI 4, 41) (p=0.016), but not on the low GI diet, 8 mm3 (95% CI-10, 26) (p=0.381). The low GI diet resulted in preservation of renal function, as eGFR, compared to the reduction following the wheat fiber diet. HbA1c was modestly reduced over the first 9 months in the intention-to-treat analysis, and extended with greater compliance to 15 months in the per-protocol analysis. </p> <p><strong>CONCLUSION:</strong> Since the low GI diet was similar to the whole wheat fiber diet recommended for cardiovascular risk reduction, the low GI diet may also be effective for CVD risk reduction. </p>