Glycemic Response to Gluten-Free Bread in Healthy Adults

Background: Research has found that nearly a quarter of the American population follows a gluten-free diet in some capacity, while only about 1% of the population is diagnosed with celiac disease. Although the amount of research-based evidence supporting any health benefits of a gluten-free diet in an individual without a gluten- related disorder is limited, the number of people claiming to follow a gluten-free diet continues to rise. Also, despite an increasing belief that gluten is harmful for health, the potentially undesirable effects of gluten substitutions used in gluten-free foods are largely unknown. Due to the protein network encapsulating starch granules, gluten is thought to lengthen the amount of time needed during starch digestion, thereby reducing postprandial glycemia. Therefore, it is predicted that breads containing gluten will produce a lower glycemic response compared to gluten-free breads. Aim: The aim of this study was to investigate the glycemic response of gluten-free bread made with different types of flour compared to bread made with gluten-containing wheat flour. Methods: This study involved a 3-week, randomized, single blind crossover study in which 17 healthy individuals were asked to consume a different type of bread each week, 2 of which were gluten-free. Blood glucose was taken by finger prick at fasting as a baseline measurement, then for 2 hours after bread consumption in 30-minute increments. Results: Across the three groups, there was no significant difference in iAUC values after 120 minutes (p=0.192 ). The greatest mean was seen in the gluten-containing bread (145.3 ± 82.6), then the gluten-free bread made with rice flour (125.5 ± 62.8), and lastly the gluten-free bread made with potato and fava bean flour (112.4 ± 64.5). Conclusion: The inconsistent results of this study compared to previous, similar studies suggests that the postprandial glycemic response of gluten-free products can not be generalized as a whole, but instead is dependent on the type of product and the ingredients used to replace the gluten. Although the results did not show a significant difference, it does argue against the belief that gluten-free products are invariably better for health in the general, non-gluten sensitive population.