The Poor Digestibility of Rapeseed Protein Is Balanced by Its Very High Metabolic Utilization in Humans 1
Abstract
Rapeseed protein (RP, Brassica napus) is used in only animal feed despite its high nutritional potential for human nutrition. We sought to assess the nutritional quality of rapeseed by measuring its real ileal digestibility (RID) and net postprandial protein utilization (NPPU) in humans fed 15 N-RP. Volunteers equipped with an intestinal tube at the jejunal (n ¼ 5) or ileal level (n ¼ 7) ingested a mixed meal containing 27.3 g 15 N-RP and a total energy content of 700 kcal (2.93 MJ). Dietary N kinetics was quantified in intestinal fluid, urine, and blood sampled at regular intervals during the postprandial period. The RID of RP was 84.0 6 8.8%. Dietary N at the ileal level was mostly in the form of undigested protein from both 12S and 2S rapeseed fractions. Aminoacidemia was not significantly increased by meal ingestion. The postprandial distribution of dietary N was 5.4 6 1.8% in urinary urea and ammonia, 8.2 6 3.4% in body urea, and 7.7 6 2.0% in plasma protein 8 h after the meal. The NPPU of RP amounted to 70.5 6 9.6% and the postprandial biological value (PBV) was high at 83.8 6 4.6%. RP has a low RID in humans compared with other plant proteins but also exhibits a very low deamination rate. Thus, the PBV of RP is excellent in humans, being as high as that of milk protein. We conclude that RP has a high nutritional potential for human nutrition.