The impact of ingestion of breads of varying composition on biomarkers of glucose metabolism in overweight and obese adults
This thesis examined the impact of ingestion of breads of varying composition on biomarkers of glucose metabolism in overweight and obese adults. In study 1, the metabolic responses to acute ingestion of 50 g available carbohydrate of 4 breads (sourdough, whole-wheat, whole-wheat barley and white) were examined after first and second meals. Ingestion of sourdough bread significantly lowered blood glucose and GLP-1 responses in the two meal periods while ingestion of whole-wheat breads did not change the metabolic responses compared to white bread. In study 2, metabolic responses to acute ingestion of whole-grain (11-grain, sprouted-grain and 12-grain), sourdough and white breads, were examined in a 2-part study. In part 1, ingestion of 50 g available carbohydrate of sprouted-grain bread significantly lowered the blood glucose response compared to sourdough and white breads. The GLP-1 response for sourdough bread was significantly lower than all the other breads. In part 2, ingestion of a fixed portion (107 g) of sprouted-grain bread significantly lowered the blood glucose and serum insulin responses compared to sourdough bread. In both study parts, the GLP-1 response for sprouted-grain bread was significantly greater than white bread. In study 3, the impact of 6 wk ingestion of 11-grain or white bread, on biomarkers of glucose metabolism was examined in metabolically challenged obese men and postmenopausal women, and healthy subjects. In the former group, 6 wk ingestion of 11-grain bread reduced the glycemic response, compared to white bread. The insulinogenic index increased post-11-grain bread, compared to post-white bread, in the control group and there was a trend (' P' =0.06) in the metabolically challenged group. Taken together, these results suggest that sourdough bread ingestion may improve postprandial glycemia while whole-wheat bread ingestion does not. Among whole-grain breads, ingestion of sprouted-grain bread lowered postprandial glycemia, while acute ingestion of 11-grain bread has no impact on glucose metabolism; this suggests that metabolic response to whole-grain breads vary among different recipes. Furthermore, chronic ingestion of 11-grain bread may improve glycemia in metabolically challenged obese population and increase insulin sensitivity in healthy population.