# The Influence of Various Types of Functional Bread on Postprandial Glycemia in Healthy Adults
## 4 Discussion
Other ingredients and their proportions, besides the addition of seeds, are also important. Adding oilseeds to bread significantly increased the content of not only fat, but also protein and fiber, and the content of protein and fat was associated with the change in postprandial glycemia,especially in the second hour after a meal. It is worth noting that, the greater the share of ingredients in the bread recipe, the higher the estimated GI of the bread. The results of this study indicated that sourdough bread has a lower GI than bread made with baker's yeast. Studies on this subject have been conducted for several decades and also often confirm this relationship [54; 55; 56; 57]. The process of sourdough fermentation, among other things, increases the number of phenolic compounds, improved protein digestibility, and improved dietary fiber composition [58]. The flour component matrix was partially loosened during sourdough fermentation and the water-extractable polyphenols can be released, which may increase their content in bread [59]. The increase in the content of polyphenols in sourdough with the lactic bacteria may also result from their proteolytic activity. Dietary polyphenols can affect postprandial glycemia through inhibition of the \(\alpha\)-amylase and \(\alpha\)-glucosidase activity and glucose absorption in the intestine by sodium-dependent glucose transporter 1 (GGLT1), the stimulation of insulin secretion, and reduction in hepatic glucose output [60]. Lower postprandial glycemia after consuming sourdough bread can be caused by various mechanisms. Starch bioavailability is decreased by interactions between gluten and starch [61] or organic acids produced by the sourdough microflora which delay gastric emptying [55; 58; 62]. Furthermore, the effect of lactic acid on amyloid enzymes causes the starch to be absorbed more slowly [55]. Bread with sourdough was also observed to have a higher resistant starch (RS) content. This may be related to the presence of organic acids promoting starch retrogradation due to baking temperature [63; 64]. Additionally, phenolic compounds are produced during sourdough fermentation, which can also lower the GI of bread [65]. The influence of the addition of sourdough in the bread-making process on the digestion and utilization of carbohydrates may be indicated by a significantly lower concentration of glucose in the blood at the end of the first hour after their consumption compared to bread with yeast. Notably, in this study, bread with both sourdough and baker's yeast had a higher glycemic response compared to sourdough bread, which may indicate a lower amount of lactic acid bacteria and lactic acid, thus, a decreased effect on lowering postprandial glycemia. Among the assessed breads, breads produced with sourdough, to a greater extent, reduced postprandial glycemia, especially in the first hour after the meal, and their IAUC value depended inversely on their fat and protein content and positively on the carbohydrate content. Additionally, the GI of sourdough bread was significantly lower than that of bread prepared with the addition of yeast (median 48.7 vs. 56.7-65.0). The glycemic index value is influenced by factors related to the type of sugars and starch, the presence of other macronutrients and antinutrients, and the technological process, such as preparation (mixing, resting time, dough storage temperature) and baking methods (time, temperature, portion size), and finally the physical form of the food. Different breads with a similar composition may look almost the same, but differences in the technological aspects, including time of individual stages of preparing and baking the dough, temperature and baking time, the use of drying, freezing, or other methods affecting the dough matrix can result in differences in the degree of starch gelatinization, absorption, and utilization, and consequently in the GI values [66]. [PERSON] et al. (2010) did not observe, however, that the dough rising method, or the addition of leavening agents, affected the GI of the bread.