Wholegrain processing and glycaemic control in type 2 diabetes: a randomised crossover trial
Research Design and Methods: Participants of this crossover trial were randomised to two interventions of two-weeks, separated by washout. They were advised to replace the grain foods they normally consumed with intervention foods. Intervention foods were nutrient matched wholegrain products of wheat, oats, and brown rice that differed in their degree of processing. No other lifestyle advice was given. Continuous glucose monitoring systems were worn. Other cardiometabolic risk factors and alkylresorcinols (a biomarker of wholegrain intake) were measured pre and post interventions.
Results: 31 adults with type 2 diabetes (63±13 years old, BMI 32.4±7, HbA1c 7.5±3.4% (59±14mmol/mol)) commenced the trial, 28 (90%) completed both interventions. The increase in alkylresorcinols did not differ between interventions and there was no difference in reported energy intake. Postprandial responses were 9% (95%CI 3-15%) lower following breakfast and 6% (95%CI 1-10%) lower following all meals of less processed whole grains when compared with finely milled grains. Day-long glycaemic variability also reduced when measured by 24-hour standard deviation (-0.16mmol/l 95%CI -0.25 to -0.06) and MAGE (-0.36 95%CI -0.65 to -0.08). Mean change in body weight differed by 0.81kg (95%CI 0.62 to 1.05) between interventions, increasing during the finely milled intervention and decreasing during the less processed wholegrain intervention. This was not a mediating factor for the glycaemic variables considered.Conclusions: Consuming less processed wholegrain foods over two weeks improved measures of glycaemia in free-living adults with type 2 diabetes when compared with an equivalent amount of wholegrain foods that were finely milled. Dietary advice should promote the consumption of minimally processed whole grains.