Acute Postprandial Glycemic Responses to Breads Made from Five Commercial Wheat-Flour Formulations: A Small Exploratory Nonrandomized Within-Participant Crossover Study

Abstract

Background/Objectives: Glycemic responses to bread vary with flour composition and processing; this study compared white bread with four specialty wheat-flour breads consumed in T & uuml;rkiye. Methods: This nonrandomized five-condition within-participant crossover study included 12 healthy adults. Test flours were a purple-labeled refined flour formulated with fruit and vegetable extracts and ascorbic acid (not purple wheat), wholemeal einkorn, refined yellow durum, and wholemeal Karak & imath;l & ccedil;& imath;k landrace. White bread was consumed first, then the test breads in two fixed, partially balanced sequences. Portions provided 50 g available carbohydrate from manufacturer-declared composition. Capillary glucose was measured at 0, 30, 60, 90, and 120 min; the primary outcome was total incremental area under the curve (iAUC). Results: Purple-flour bread had 32% lower total iAUC (Holm-adjusted p = 0.035) and early iAUC (0-60 min; p = 0.041) than white bread. The early contrast held in the Wilcoxon test (p = 0.049), whereas interpretation of the total iAUC contrast depended on the model: it reached significance in neither rank-based Wilcoxon (p = 0.064) nor log-transformed (p = 0.058) analyses. In exploratory comparisons, purple-flour bread had lower early iAUC than the other test breads and lower total iAUC than yellow durum (all Holm-adjusted p <= 0.016). Conclusions: The purple formulation was associated with lower early glycemic exposure, einkorn with intermediate and yellow durum with the highest responses; Karak & imath;l & ccedil;& imath;k did not differ significantly from white bread. Higher declared fiber content was not consistently associated with lower acute glycemic responses in the products tested. Findings apply only to the formulations tested and require confirmation in randomized, counterbalanced studies with verified composition.