The influence of the albumin fraction on the bioavailability and postprandial utilization of pea protein given selectively to humans

Pulse seed proteins such as those found in peas (Pisum sativum) contain fra ctions of very dissimilar composition and properties, which may therefore b e differently utilized by the human body. To analyze the nutritional value of the soluble protein fractions of pea seed, human volunteers ingested a m ixed meal of 30 g of raw purified pea protein either as [N-15]-globulins (G , n = 9) or as a mix of [N-15]-globulins and [N-15]-albumins (GA, n = 7) in their natural proportions (22.8). Dietary and endogenous nitrogen fluxes a t the terminal ileum were assessed using a tube perfusion technique with an isotopic dilution method. Systemic dietary amino acid availability and the retention of dietary amino acids were determined using 15N enrichment in p lasma amino acids and deamination products in blood and urine for 8 h postp randially. The results showed that the pea albumin fraction had the followi ng effects: 1) significantly lowered the real ileal digestibility of pea pr otein (94 +/- 2.5% for G vs. 89.9 +/- 4% for GA), probably because of a dir ect effect of trypsin inhibitors; 2) did not promote acute intestinal losse s of endogenous nitrogen; and 3) did not significantly improve the postpran dial biological value of pea protein (76.5 +/- 3.9% for G vs. 78.7 +/- 3.6% for GA), despite the fact that it corrected the globulin deficiency in sul fur amino acids. We conclude that both G and GA are of good nutritional val ue for humans and show that cysteine-rich albumins have a far more modest e ffect on the efficiency of postprandial dietary protein utilization than wo uld be expected from the amino acid scores.