Dietary Fiber for the Treatment of Type 2 Diabetes Mellitus

A Meta-analysis

Robert E. Post, MD, MS; Arch G. Mainous III, PhD; Dana E. King, MD, MS; Kit N. Simpson, DrPH

Disclosures

J Am Board Fam Med. 2012;25(1):16-23. 

In This Article

Abstract and Introduction

Abstract

Background: The evidence of the relationship between fiber intake and control of diabetes is mixed. The purpose of this study was to determine if an increase in dietary fiber affects glycosylated hemoglobin (HbA1c) and fasting blood glucose in patients with type 2 diabetes mellitus.
Methods: Randomized studies published from January 1, 1980, to December 31, 2010, that involved an increase in dietary fiber intake as an intervention, evaluated HbA1c and/or fasting blood glucose as an outcome, and used human participants with known type 2 diabetes mellitus were selected for review.
Results: Fifteen studies met inclusion and exclusion criteria. The overall mean difference of fiber versus placebo was a reduction of fasting blood glucose of 0.85 mmol/L (95% CI, 0.46–1.25). Dietary fiber as an intervention also had an effect on HbA1c over placebo, with an overall mean difference of a decrease in HbA1c of 0.26% (95% CI, 0.02–0.51).
Conclusion: Overall, an intervention involving fiber supplementation for type 2 diabetes mellitus can reduce fasting blood glucose and HbA1c. This suggests that increasing dietary fiber in the diet of patients with type 2 diabetes is beneficial and should be encouraged as a disease management strategy.

Introduction

Diabetes mellitus is an ever increasing problem in the United States. As of 2010, the Centers for Disease Control and Prevention estimates that there are 18.8 million people affected with this disease in the United States with another 7 million people with undiagnosed diabetes.[1] Furthermore, almost 2 million people older than the age of 20 were newly diagnosed with diabetes in 2010.[1] Diabetes was estimated to cost more than $174 billion in 2007 in the United States when taking into account medical costs and loss of productivity.[2] Diabetes increases mortality by almost 2-fold and increases mortality by cardiovascular disease by 2- to 3-fold.[3]

Lifestyle modification is an important part of the management of diabetes. One of the main strategies for this is known as "medical nutrition therapy." The goals of medical nutrition therapy include improving control of blood glucose levels, lipid profiles, and blood pressure to reduce the risk of cardiovascular disease in patients with type 2 diabetes mellitus.[4] Medical nutrition therapy has been shown to reduce glycosylated hemoglobin (HbA1c) by 1% to 2% in patients with type 2 diabetes mellitus.[5] It also has been shown to cause improvements in low-density lipoprotein cholesterol, an important marker in controlling the risk of cardiovascular disease.[6] The American Diabetes Association recommends a specific diet as part of medical nutrition therapy for secondary and tertiary prevention in patients with type 2 diabetes mellitus. This diet includes the consumption of fiber-rich foods.[4]

Fiber has been studied in the treatment of diabetes for many years because increased fiber content decreases the glycemic index of foods.[7–9] The theory, then, is that the decreased glycemic index would lead to smaller increases in blood glucose, and thus reduced blood glucose and HbA1c levels. Although high fiber intake has been linked to a decreased risk of diabetes,[10,11] the evidence on fiber intake and control of diabetes is mixed. Specifically, many of the studies focused on fiber intake and glycemic control are small and have conflicting results; some studies show an improvement in diabetes control and others show no improvement.[12–17] Therefore, the purpose of this study was to perform a meta-analysis of these studies to determine to what extent an increase in dietary fiber affects HbA1c and fasting blood glucose in patients with type 2 diabetes mellitus.

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