The acute impact of ingestion of sourdough and whole-grain breads on blood glucose, insulin, and incretins in overweight and obese men

Abstract

Consumption of whole-grain and sourdough breads is associated with improved glucose homeostasis. We examined the impact of commercial breads on biomarkers of glucose homeostasis in subjects at risk for glucose intolerance. In a randomized, crossover study, overweight or obese males ingested 11-grain, sprouted-grain, 12-grain, sourdough, or white bread on different occasions, matched for available carbohydrate (50 g) in part 1 (n = 12) and bread mass (107 g) in part 2 (n = 11), and blood glucose, insulin and glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were determined for 3 h. In part 1, glucose response for sprouted-grain was lower than 11-grain, sourdough, and white breads. Insulin area under the curve (AUC) for sourdough and white was lower than 11-grain and sprouted-grain breads. GLP-1 response to sourdough was lower than all breads. In part 2, glucose and insulin AUC for sourdough was greater than 11-grain, sprouted-grain, and 12-grain breads. Sprouted-grain bread improved glycemia by lowering glucose response and increasing GLP-1 response. In overweight and obese men, the glycemic response to sprouted grain bread was reduced in both parts 1 and 2 while the other whole-grain test breads did not improve metabolic responses in the acute postprandial state.

Figure 1

Fasting and postprandial glucose responses to the ingestion of 50 g available carbohydrate of the test breads. Data are means. Standard errors are not included for clarity, n = 12. Test bread was ingested after collection of fasting blood sample at time point −15 min. Significant overall treatment effects were found in glucose responses to the breads (Sprouted-grain bread was lower than 11-grain (P < 0.009), sourdough (P < 0.001), and white (P < 0.006) breads). Twelve-grain bread was lower than 11-grain (P < 0.04) and sourdough (P < 0.003) breads).

Figure 2

Fasting and postprandial insulin response to the ingestion of 50 g available carbohydrate of the test breads. Data are means. Standard errors are not included for clarity, n = 12. Test bread was ingested after collection of fasting blood sample at time point −15 min. Significant overall treatment effects were identified (11-grain bread was greater than sourdough (P < 0.005) and white (P < 0.03) breads).

Figure 3

Fasting and postprandial GLP-1 responses to the ingestion of 50 g available carbohydrate of the test breads. Data are means. Standard errors are not included for clarity, n = 11. Test bread was ingested after collection of fasting blood sample at time point −15 min. Significant overall treatment effects were found (sourdough bread was lower than 11-grain (P < 0.0001), sprouted-grain (P < 0.0001), and white (P < 0.02) breads. 11-grain bread was greater than 12-grain (P < 0.03) and white (P < 0.03) breads. Sprouted-grain bread was greater than 12-grain (P < 0.009) and white (P < 0.05) breads).

Figure 4

Fasting and postprandial insulin responses to the ingestion of a consistent amount of the test breads. Test bread was ingested after collection of fasting blood sample at time point −15 min. Data are means. Standard errors are not included for clarity, n = 11. Significant overall treatment effects were found in insulin response to the breads (sprouted-grain bread was lower than 12-grain (P < 0.03) bread, and 12-grain bread was lower than sourdough (P < 0.001) and white (P < 0.001) breads).

Figure 5

Fasting and postprandial GIP responses to the ingestion of a consistent amount of the test breads. Data are means. Standard errors are not included for clarity, n = 11. Test bread was ingested after collection of fasting blood sample at time point −15 min. A significant overall treatment effect was found (11-grain bread was lower than sourdough (P < 0.008) bread).

Figure 6

Fasting and postprandial GLP-1 responses to the ingestion of a consistent amount of the test breads. Data are means. Standard errors are not included for clarity, n = 10. Test bread was ingested after collection of fasting blood sample at time point −15 min. Significant overall treatment effects were found (sprouted-grain bread was greater than 11-grain (P < 0.008), sourdough (P < 0.001), 12-grain (P < 0.04), and white (P < 0.04) breads).