Measurements of the gastric emptying rate by use of ultrasonography: studies in humans using bread with added sodium propionate

BACKGROUND: Foods with a low glycemic index are increasingly being acknowledged as beneficial for individuals with disorders related to the insulin resistance syndrome. The presence of certain salts of organic acids has been shown to lower the glycemic index of bread products and one of the suggested mechanisms is a lowered gastric emptying rate (GER). One obvious pitfall with many of the common techniques for GER measurement is that the food structure, and hence the gastric release of nutrients, may be affected by enclosure of the marker for gastric emptying, eg, paracetamol. Ultrasonography is a noninvasive method for which the above pitfall is to a large extent avoided. OBJECTIVE: The main objective was to evaluate the use of ultrasonography to determine whether the lowered glycemic and insulinemic responses to bread ingestion after the addition of sodium propionate are explained by a specific effect of propionate on the GER. DESIGN: The effect of sodium propionate in bread was evaluated in 9 healthy volunteers. Barley bread products, with or without added sodium propionate, were ingested as breakfast after an overnight fast. The GER was monitored for 2 h by ultrasonography; during this period, capillary blood was withdrawn repeatedly for measurement of blood glucose and insulin. RESULTS: The GER of the barley bread decreased markedly after the addition of sodium propionate and was accompanied by lowered glycemic and insulinemic responses. CONCLUSION: The lowered glycemic response to ingestion of bread with added sodium propionate appears to be related to a lowered GER.