amino acids energy and protein metabolism human nutrition and metabolism nitrogen isotopes oxidation albumin arginine bioavailability cysteine dietary fiber endothelial function exercise food labeling globilin glutathione guar gum health claims human nutrition humans ileal digestibility liver lupin protein metabolism and metabolic studies nitrogen nutrient metabolism pea protein pharmacokinetics plant protein postprandial retention protein metabolism protein utilization public health soyabean protein stable isotope urea kinetics viscosity