Impact of dietary fiber intake on insulin resistance in type 2 diabetes: A systematic review

Abstract

This systematic review examines the impact of dietary fiber intake on insulin resistance in individuals with type 2 diabetes mellitus (T2DM). Given the global rise in T2DM prevalence and the central role of insulin resistance in its pathophysiology, there is an increasing emphasis on nonpharmacological interventions, such as dietary fiber, to manage glycemic outcomes. A comprehensive search was conducted across six databases including PubMed, Scopus, Web of Science, ProQuest, CINAHL, and CENTRAL, focusing exclusively on randomized controlled trials (RCTs) up to June 2022. Thirteen RCTs, involving a total of 641 participants, were included in the final synthesis. The interventions varied in fiber type (soluble, insoluble, and mixed), source (whole grains, legumes, flaxseed, composite flour), and dosage (5–50 g/day), with durations ranging from 1 to 6 months. Findings consistently demonstrated that dietary fiber, especially soluble and mixed types, significantly improved insulin resistance as measured by HOMA-IR and related indices. Additionally, notable improvements were observed in fasting glucose, HbA1c, LDL cholesterol, and body weight in several trials. While the results are promising, limitations, such as short study durations, small sample sizes, heterogeneity in intervention protocols, and limited long-term data, constrain broader generalization. Despite these challenges, the evidence strongly supports dietary fiber as an effective adjunct in managing insulin resistance in T2DM. The review underscores the need for longer-duration, multicenter RCTs with standardized fiber interventions to confirm findings and inform clinical practice. Dietary fiber should be integrated into individualized diabetes management strategies to enhance metabolic outcomes and overall health.