Reference Number: 83
Sourdough bread has been reported to improve glucose metabolism in healthy subjects. In this study postprandial glycaemic and insulin responses were evaluated in subjects with impaired glucose tolerance (IGT) who had a meal containing sourdough bread leavened with lactobacilli, in comparison to a reference meal containing bread leavened with baker yeast. The study was carried out using a mixed meal not only for making it more palatable but because it was suggested that the overall diet pattern, instead of single nutrients, which might have a synergistic or antagonistic effect on health
Sixteen IGT subjects (age range 52–75, average BMI 29.9 ± 4.2 kg/ m2 ) were randomly given a meal containing sourdough bread (A) and a meal containing the reference bread (B) in two separate occasions at the beginning of the study and after 7 days. Sourdough bread was leavened for 8 h using a starter containing autochthonous Saccharomyces cerevisiae and several bacilli able to produce a significant amount of D -and L -lactic acid, whereas the reference bread was leavened for 2 h with commercial baker yeast containing Saccharomyces cerevisiae . Plasma glucose and insulin levels were measured at time 0, 30, 60, 120, and 180 min.
In IGT subjects sourdough bread induced a significantly lower plasma glucose response at 30 minutes (p = 0.048) and a smaller change at 0–30 and 0–60 min (p = 0.020 and 0.018 respectively) in comparison to the bread leavened with baker yeast. Plasma insulin response to this type of bread showed lower values at 30 min (p = 0.045) and a smaller change 0–30 min (p = 0.018). This study shows that in subjects with IGT glycaemic and insulin responses after the consumption of sourdough bread are lower than after the bread leavened with baker yeast. This effect is likely due to the lactic acid produced during dough leavening as well as the reduced availability of simple carbohydrates. Thus, sourdough bread may potentially be of benefit in subjects with impaired glucose metabolism.
SIGNIFICANCE OF THIS STUDY
This study confirms that sourdough bread has a reduced glycemic index compared to baker’s yeast bread and this is further emphasised by a reduced insulin requirement as reported in a previous study (ref. study number 182). This is of great importance as it has been reported that even short bursts of hyperglycaemia may worsen insulin resistance in diabetic patients. Therefore these findings suggest that a diet program including sourdough bread may contribute to delay the evolution of IGT to diabetes. Finally, a lower postprandial hyperglycaemia elicited by sourdough bread could may lower the risk of further health complications in patients with diabetes. Further research is however needed to study the long term effects of sourdough bread on glycemic and insulin response.