An 8-week diet high in cereal fiber and coffee but free of red meat does not improve beta-cell function in patients with type 2 diabetes mellitus: a randomized controlled trial.

Background: Higher dietary intake of fibers and coffee, but lower red meat intake is associated with reduced risk for type 2 diabetes in epidemiological studies. We hypothesized that a calorie-restricted diet, which is high in fiber and coffee, but free of red meat, improves beta-cell function in patients with T2D.

Methods: In a randomized parallel-group pilot trial, obese type 2 diabetes patients were randomly allocated to consume either a diet high in cereal fiber and coffee, but free of red meat ( = 17) (L-RISK) or a diet low in fiber, free of coffee but high in red meat ( = 20) (H-RISK) for 8 weeks. Insulin secretion was assessed from glucagon stimulation tests (GST) and mixed-meal tolerance tests (MMTT) before and after dietary intervention.

Results: Both diets resulted in comparable reduction of fasting concentrations of insulin (H-RISK -28% vs. L-RISK -32%,  < 0.01), C-peptide (H-RISK -26% vs. L-RISK -30%,  < 0.01) and blood glucose (H-RISK -6.8%,  < 0.05 vs. L-RISK -10%,  < 0.01). Gastric inhibitory peptide (GIP) secretion increased by 24% after 8 weeks in the L-RISK only ( < 0.01). However, GST and MMTT showed no differences in insulin secretion after intervention.

Conclusions: Calorie restriction independent of the intake of fiber, coffee or meat failed to improve beta-cell function, but improved GIP secretion in obese patients with type 2 diabetes.

Trial Registration: Registration at Clinicaltrials.gov, Identifier number: NCT01409330, Registered 4 August 2011 - Retrospectively registered.