Research

Exponential increase in postprandial blood-glucose exposure with increasing carbohydrate loads using a linear carbohydrate-to-insulin ratio

Kerry Joan Marran, Beverley Davey, Alison Lang, David Grant Segal

Abstract


Background. Postprandial glucose excursions contribute significantly to average blood glucose, glycaemic variability and cardiovascular risk. Carbohydrate counting is a method of insulin dosing that balances carbohydrate load to insulin dose using a fixed ratio. Many patients and current insulin pumps calculate insulin delivery for meals based on a linear carbohydrate-to-insulin relationship. It is our hypothesis that a non-linear relationship exists between the amounts of carbohydrate consumed and the insulin required to cover it.

Aim. To document blood glucose exposure in response to increasing carbohydrate loads on fixed carbohydrate-to-insulin ratios.

Methods. Five type 1 diabetic subjects receiving insulin pump therapy with good control were recruited. Morning basal rates and carbohydrate- to-insulin ratios were optimised. A Medtronic glucose sensor was used for 5 days to collect data for area-under-the-curve (AUC) analysis, during which standardised meals of increasing carbohydrate loads were consumed.

Results. Increasing carbohydrate loads using a fixed carbohydrate-to-insulin ratio resulted in increasing glucose AUC. The relationship was found to be exponential rather than linear. Late postprandial hypoglycaemia followed carbohydrate loads of >60 g and this was often followed by rebound hyperglycaemia that lasted >6 hours.

Conclusion. A non-linear relationship exists between carbohydrates consumed and the insulin required to cover them. This has implications for control of postprandial blood sugars, especially when consuming large carbohydrate loads. Further studies are required to look at the optimal ratios, duration and type of insulin boluses required to cover increasing carbohydrate loads. 


Authors' affiliations

Kerry Joan Marran, Department of Paediatric Endocrinology, Charlotte Maxeke Academic Hospital, Johannesburg, South Africa

Beverley Davey, Donald Gordon Medical Centre, University of the Witwatersrand, Johannesburg, South Africa

Alison Lang, Donald Gordon Medical Centre, University of the Witwatersrand, Johannesburg, South Africa

David Grant Segal, Department of Paediatric Endocrinology, Charlotte Maxeke Academic Hospital, Johannesburg, South Africa

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Keywords

carbohydrate; insulin; ratio; post-prandial;diabetes

Cite this article

South African Medical Journal 2013;103(7):461-463. DOI:10.7196/SAMJ.6382

Article History

Date submitted: 2012-10-08
Date published: 2013-04-10

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