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 3 sourdough bread (SB) versus standard baker’s yeast bread (BYB) in healthy young adults. Thirteen healthy subjects [age: 30 (29-33) years, BMI: 23.4 (22.4-25.1 kg/m2); data are expressed as median (1st-3rd quartile)] 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, Resting 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 and positive incremental Area Under the Curve (iAUC) between SB and BYB. No significant time-treatment interaction was observed for insulin (p>0.1), 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) and hunger or satiation hormones (total and acylated ghrelin, GLP-1, GIP, Leptin, PYY) were not significantly affected by treatment type (all p>0.1). However, a significant effect on zonulin total area under the curve by treatment was apparent (p>0.02). Although the favorable in vitro characteristics of sourdough bread did not lead to a substantial superiority for Type 3 SB over BYB regarding in vivo postprandial glyco-metabolic parameters, a modulating effect on zonulin holds promise for future trials focusing on subjects with altered intestinal permeability.