Year: 2014
Type: article
Abstract: (pdf)Glycaemic response to carbohydrate-containing foods is a combination of glucose absorption, endogenous glucose production, and tissue glucose uptake.After a carbohydrate-containing meal, blood glucose rises, which stimulates insulin secretion.The different amount and type of carbohydrates influence postprandial glucose and insulin responses differently.The concept of the glycaemic index (GI) was developed to rank carbohydrates according to their effect on blood glucose levels.Food with a low GI value is considered beneficial in maintaining optimal blood glucose due to smaller incremental increase in blood glucose than food with a high GI value.Foods characterized by a low GI therefore have been found to induce benefits on several risk markers related to type 2 diabetes and cardiovascular disease.The concept of the GI was originally developed as a tool for individuals with diabetes in choosing the most beneficial carbohydrate-rich foods regarding blood glucose responses.To assess the extent to which eaten food raises insulin levels, the concept of the insulinaemic index (II) was launched.The calculation of II values is performed similarly to GI values.The concept of GI has been widely studied and debated in the scientific literature.The main aim of this thesis was to investigate the effect of methodological choices on measured glucose and insulin responses, especially on GI values.To achieve these goals, five different postprandial studies were conducted in healthy individuals and in individuals with impaired glucose tolerance.Capillary and venous blood samples were collected up to 2-3 h postprandially and the incremental area under the curve (IAUC), GIs, and IIs were calculated.In the first study, the effects of methodological choices on measured glycaemic response and GI values were determined.Comparisons were done between blood sampling type (capillary vs. venous blood samples), type of reference food (white bread vs. glucose solution), and how many times the reference food should be repeated.Results revealed that the variation was smaller when capillary samples were used, performing the reference food test twice is sufficient, and to achieve better accuracy the glucose solution should be used as the reference food.In the second study, the effects of coffee on postprandial glucose and insulin responses were determined.Coffee as such does not modify the glucose and insulin responses of a carbohydrate food.Coffee had no marked effect on GI values.In the third study, the effects of subjects' physiological characteristics, namely glucose tolerance and overweight, on postprandial glucose and insulin responses were examined.Both overweight and impaired glucose tolerance increased glycaemic and insulinaemic responses to the tested meals and the reference food.As a consequence, physiological characteristics did not affect the measured GI values.In the fourth study, the effects of other macronutrients, namely fat and protein, on glycaemic responses to a starchy food were examined.Both fat and protein have an independent decreasing effect on glycaemia, and as a consequence, GI values Challenges in MeasuringGlycaemice Index diminished.Insulin responses to the meals were also measured.Adding protein to the mashed potato-based meals considerably enhanced insulin responses to the meal.In the fifth study, the effects of alcohol on postprandial glucose and insulin responses were determined.Alcohol was found to increase postprandial glucose and insulin responses, probably through acutely increased insulin resistance.In addition, high GI values were measured for both beer and non-alcoholic beer.This should be taken into account when GI databases are compiled for epidemiologic studies.In summary, several factors affect measured GI values, highlighting that different methodological choices should be carefully considered.The use of recent international standards, for measuring GI values is highly recommended, and GI values measured prior to the standard should be interpreted and utilized with caution.To increase the reliability of GI measurements in the future, GI should be measured in combination with II measurements.
Author: Katja A. Hätönen
Language: English
Subfield: Nutrition and Dietetics
Field: Nursing
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W1926445953