Determination of glycemic index values of some gluten-free breads sold in the market

The use of gluten-free products have became widespread in recent years, however, the information about the nutritional values and glycemic effects of these products is very limited. This study aimed to determine the glycemic index value of some gluten-free breads sold in the market in Turkey, and thus to contribute to the further clinical studies in this field. The study was conducted on 12 adults aged 19-35 years (27.3 ± 2.35 years) with a body mass index between 18.5-24.99 kg/m2 (22.5 ± 1.97 kg/m2). Participants visited the research center 11 times in total by intervals of 4 to 10 days in order to determine the glycemic index values of two reference foods (white bread and glucose) and nine different gluten-free breads. At each visit, participants consumed reference or test food that contains 25 g of available carbohydrate following the capillary fasting blood glucose measurement and fasting-toughness score assessment with 100-mm VAS, and then the measurements were repeated after 15, 30, 45, 60, 90, and 120 minutes of the consumption. When the reference is glucose, the glycemic index values of gluten-free breads were ordered as C brand gluten-free crisp bread (87.3), E brand gluten-free bread (82.7), white bread (80.3), B brand gluten-free crisp bread (74.5), C brand gluten-free daily bread (63.1), A brand gluten-free bread (61.5), F brand gluten-free bread (58.0), D brand protein reduced baguette bread (51.7), D brand protein reduced small bread (47.1) and B brand gluten-free home bread (42.4). Four breads (C brand gluten-free crisp bread, E brand gluten-free bread, and B brand crisp bread) were categorised as high glycemic index (≥70); three breads (C brand gluten-free daily bread, A brand gluten-free bread and F brand gluten-free bread) were categorised as medium glycemic index (56-69), and the other three (D brand protein reduced baguette bread, D brand protein reduced bread and B brand gluten-free home bread) were categorised as low glycemic index (≤55). When the reference is white bread, all gluten-free breads had high glycemic index (≥70). The glycemic index of breads were decreased by the increased content of fiber (r= -0.265, p=0,003). B brand gluten-free crisp bread showed a positive correlation between the incremental area under the blood glucose response curve and the toughness scores (r= 0.580, p=0.048) while C brand gluten-free bread showed a negative correlation between the same parameters (r= -0.706, p=0.010). Furthermore, C brand gluten-free daily bread showed positive correlations between the incremental area under the blood glucose response curve and all of fasting, edible amount and desire to eat scores were found (r=0.762, p=0.004; r= 0643, p=0.024; r= 0.692, p=0.013, respectively). Conversely, a negative correlation between incremental area under the blood glucose response curve of F brand gluten-free bread and the desire to consume sugary foods were obtained (r= -0.629, p=0.028). Reformulation of gluten-free products that provides a decline in glycemic index values of these products is required, and also it is important to ensure that such products are preferred by consumers.