Thesis title: Effect of sourdough fermentation on metabolic and satiation parameters in a sample of healthy adults
The growing use of sourdough fermentation for bread making is driven by its potential to modify the glycemic profile and reduce antinutritional factors (e.g., phytates, lectins, gluten). However, previous scientific literature has shown inconsistency, making it uncertain whether these in vitro alterations translate into definitive, clinically relevant health benefits. This randomized, crossover, in vivo study aimed to compare the metabolic and satiation effects of consuming bread fermented with Type II sourdough bread (SB) versus standard baker’s yeast bread (BYB) in healthy young adults. Thirteen healthy subjects (age 30.31±3.88, BMI 23.45±2.21) completed both treatments, with portions standardized to 50 grams of available carbohydrates. Biochemical characterization confirmed that SB exhibited significantly higher acidity (lower pH, higher TTA) and Total Free Amino Acids (TFAA) (p<0.05). Crucially, SB showed significantly higher in vitro protein digestibility (IVPD: 74.3±1.1%) and a lower predicted Glycemic Index (pGI: 80.5±0.6%) compared to BYB (IVPD: 63.7±1.9%, pGI: 94.6%). Metabolic outcomes, including postprandial glucose, insulin, esting Energy Expenditure (REE), Respiratory Quotient (RQ), and Thermic Effect of Food (TEF), were measured up to 180 minutes. Analysis of glucose homeostasis showed no statistically significant overall difference in postprandial glycemia or glucose net incremental Area Under the Curve (net iAUC) between SB and BYB. While a significant time-treatment interaction was observed for insulin (p=0.046), resulting in transiently higher insulin levels after SB at 15 minutes (p<0.001), the overall insulin net iAUC did not differ significantly (p=0.128). Furthermore, metabolic parameters related to energy expenditure (REE, RQ, and TEF) were not significantly affected by treatment type. Despite the confirmed favorable in vitro characteristics of sourdough bread—attributed to biological acidification promoting beneficial changes like amylose retrogradation and increased protein digestibility—the study found no substantial superiority for Type II sourdough bread over baker’s yeast bread regarding postprandial glucose, overall insulin response, or resting energy expenditure in a cohort of healthy young subjects.