Partial starch substitution with resistant starch lowers postprandial glucose and glycaemic variability in people with type 2 diabetes

Aims

Approximately 40% of the caloric intake of the UK diet consists of starch. Most of which is readily digestible, thereby raising blood glucose. However, resistant starch (RS) evades metabolism in the small intestine, and in healthy adults, partial substitution of the diet with RS lowers postprandial glycaemia. The effect of RS in adults with type 2 diabetes is unknown.

Methods

We investigated the effect of substituting ~15% of dietary starch with RS on glycaemic measures in adults with type 2 diabetes in a controlled but free-living setting. This was a single-blinded, crossover design, comparing 4-day RS and control diets. Proportions of resistant and digestible starch in identical food products were the only difference. IPro™2 continuous glucose monitors captured glycaemic excursions and glycaemic variability.

Results

Twenty adults with type 2 diabetes, HbA_1c (52 ± 2 mmol/mol; 6.9 ± 0.3%), age 58 ± 11 years, were enrolled, with 95% completing arms. Mean amplitude of glycaemic excursion (MAGE) was lower over lunch with RS (0.94 mmol/L; p = 0.004), as was SD glucose (0.31 mmol/L; p = 0.027), and peak glucose (0.94 mmol/L; p = 0.028). RS prolonged the time it took glucose to peak by 18 min at lunch (p = 0.046) and 28 min at dinner (p = 0.002). Time in range (TIR; glucose 3.9–10.0 mmol/L) was 7.8% greater with RS (p = 0.021).

Conclusion

Substituting a proportion of starch with RS lowers blood glucose without changing the sensory attributes of foods significantly. There is potential to develop a functional diet for adults with type 2 diabetes to aid glycaemic control.