Randomised controlled trials (RCTs) that involved an increase in dietary fibre as an intervention versus control in patients with type 2 diabetes mellitus were eligible for inclusion. Trials had to report on glycosylated haemoglobin or fasting blood glucose as an outcome. Trials in which two types of dietary fibre were compared or where diets were dissimilar between groups were excluded.
The included trials studied various forms of soluble and insoluble fibre (including cereal, guar gum, beet fibre and wheat fibre). The increase in dietary fibre compared with the control group ranged from 4g to 40g. Where reported, the mean age of patients ranged from 51.9 to 69.1 years. Trials were published between 1984 and 2007. More than half of the trials were randomised cross-over design.
The authors did not state how many reviewers undertook study selection.