# The Influence of Various Types of Functional Bread on Postprandial Glycemia in Healthy Adults
## 4 Discussion  
Bread is one of the oldest and most convenient food products commonly consumed by people worldwide. By promoting bread that can boost health, including reducing postprandial glycemia and the risk of metabolic syndrome [30], informed dietary choices can be promoted as part of a sustainable diet. The current study attempted to characterize the relationship between the composition and nutritional value of different types of bread and postprandial glycemic response values. The postprandial glycemic response and, thus, glycemic index (GI) value of food is influenced by various factors, which can be broadly categorized into the macronutrient composition, type of carbohydrate, fiber content, food processing methods, presence of anti-nutrients, and individual physiological differences [10; 30]. The amylose, resistant starch (RS), dietary fiber, lipid, protein content, and phenolic flavonoid presence in food significantly reduce starch hydrolysis and lower the GI value [31]. Considering all the bread tested, our study indicated negative relationships between incremental areas under the glycemic response curve (IAUC) elicited by the tested food and protein, fat content, and fiber/carbohydrate ratio. In addition, tested products containing more than 5.9 g of fat per 100 g portion (median of fat) had a significantly lower glycemic index value than those with a fat content below 5.9 g. These associations align with previous data [31; 32]. Higher fat content has the potential to delay gastric emptying, which results in slower digestion and glucose absorption [32]. Concerning the protein content, we have shown that it significantly affects the postprandial glycemic response, which may be linked to the stimulation of insulin secretion that blunts postprandial hyperglycemia during the monitored period [33]. However, this observation was not associated with a significant relationship between protein content and glycemic index value in our study. Comparing the nutritional value and the effect of postprandial glycemic response according to dominant flour, we observed statistically lower median values for GI and IAUC for the group with dominant rye flour than the wheat/spelt group. This may be due to differences in the type and composition of cereals used to produce the flour. Rye generally contains less starch and crude protein than wheat but has a significantly higher dietary fiber content, the highest among common cereals [34; 35]. This was also observed in our tested products--the group of bread with predominantly rye flour was characterized by a significantly higher content (median value) of dietary fiber (per 100 g) compared to the other two groups (6.8 g vs. 6.0 and 6.1 g, respectively). The main components of rye's dietary fiber include arabinoxylan, \(\beta\)-glucan, fructan, cellulose, and lignin, while the first three components are more abundant than in wheat [33; 34]. Arabinoxylan and \(\beta\)-glucan are associated with the viscous properties of soluble dietary rye fiber, which may promote the technological functionality and various beneficial health effects of rye. Dietary fiber can play a role in glycemic control by decreasing gastric emptying, modulating gastrointestinal hormone secretion, suppressing alpha-amylase activity, and inhibiting the hydrolysis of starch, thereby reducing the rate of digestion and absorption of starch-rich products [10; 31]. Regarding the protein and fat content which was significantly higher in the wheat/spelt-based flour group than in the rye flour group, it is possible that fiber content or structural differences between wheat and rye played a more significant role in the reduction in postprandial glycemia and thus the glycemic index values than other nutrients [35; 36; 37]. However, there was a negative association between IAUC and protein content in both groups and only in the rye group--an inverse relationship between IAUC and fat and dietary fiber content. Additionally, fat content in both groups was negatively related to glycemic index value.