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

Results

Studies

The search initially yielded 1623 studies. Of these, 28 met inclusion criteria. Of these 28 studies, 13 were excluded for meeting one of the exclusion criteria, resulting in a total of 15 studies (Figure 1). Of the 15 included studies, 5 were randomized controlled trials[19–23] and 10 were randomized crossover trials.[24–33] Among these 15 articles, 13 contained data for fasting blood glucose that could be extracted and 10 contained data for HbA1c that could be extracted. Further details regarding the types of fiber and the specific interventions used in each study are listed in Table 1. Using the GRADE assessment, 11 of the studies were of high quality and 4 were of moderate quality.

Demographics

Table 2 lists the demographic features of each study. The total number of participants for fasting blood glucose was 400 and for HbA1c was 324. Mean ages ranged from 52.1 to 69.1 years. The proportion of female participants ranged from 7.7% to 73.4%. Mean body mass index ranged from 23.4 to 32.5. Fiber interventions ranged from 4 to 40 g/d of additional fiber, with a mean increase in fiber for the intervention of 18.3 g/d. No studies reported any bias.

Fasting Blood Glucose

Results for the meta-analysis of fasting blood glucose are shown in Figure 2. Because the test for heterogeneity was not statistically significant (P = .40), the fixed-effects model was considered valid for the analysis. Overall, fiber intervention was more effective than placebo in reducing fasting blood glucose. The overall mean difference was a reduction of fasting blood glucose by fiber of 0.85 mmol/L (95% CI, 0.46–1.25) more than the reduction from placebo. This is equivalent to a reduction over placebo of 15.32 mg/dL (95% CI, 8.29–22.52). The funnel plot for fasting blood glucose data are fairly symmetrical, with 7 studies favoring fiber and 6 favoring control, indicating low risk of publication bias for this data.

Figure 2.

Forest plot for fasting blood glucose. Mean, SD, and mean difference are shown in units of mmol/L.

Glycosylated Hemoglobin

Results for the meta-analysis of HbA1c are shown in Figure 3. Because the test for heterogeneity was not statistically significant (P = .25), a fixed-effects model was considered valid for analysis. Overall, fiber intervention was more effective on HbA1c than placebo, with an overall reduction in HbA1c by fiber of 0.26% (95% CI, 0.02–0.51) more than the reduction from placebo. The funnel plot for HbA1c data is asymmetrical, indicating that there may be a risk of publication bias for this data.

Figure 3.

Forest plot for glycosylated hemoglobin.

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