Nanoscale materials derived from natural biopolymers like cellulose and chitosan have many potentially useful agri-food and oral dnig delivery applications. Because of their large and potentially bioactive surface areas and other unique physico-chemical properties, it is essential when evaluating their toxicological impact to assess potential effects on the digestion and absorption of co-ingested nutrients. Here, the effects of cellulose nanofibers (CNF), cellulose nanocrystals (CNC), and chitosan nanoparticles (Chnp) on the digestion and absorption of carbohydrates were studied. Starch digestion was assessed by measuring maltose released during sinuilated digestion of starch solutions. Glucose absorption was assessed by measuring translocation from the resulting digestas across an in vitro transwell tn—culture model of the small intestinal epithelium and calculating the area under the curve increase in absorbed glucose, analogous to the glycemic index. At 10/0 wiw, (NF and Chnp had small but significant effects (11% decrease and 14% increase, respectively) and CNC had no effect on starch hydrolysis during simulated digestion of a 1%w/w rice starch solution.