Under-nutrition and related health problems are widespread in India, and food quality, rather than quantity is one of the key issues (1). Many recent meetings of International organizations have addressed major issues pertaining to the dietary protein intake and its bioavailability.  FAO released a Dietary Protein Quality Evaluation Report in 2011 (2), which was a preface to the 2012 WHO technical note on foods for the management of moderate acute malnutrition in children (3). Further to this, an Expert Consultation in October 2013 was held to discuss various stable isotopic based methods to measure protein quality in humans (4). Protein bioavailability is measured from oro-ileal balance studies. Since absorption occurs only in the small intestine and colonic bacteria can recycle nitrogen, it is impossible to measure it non-invasively in humans. Hence, the use of intrinsic labeled protein is the best approach to measure bioavailability of indispensable amino acids (IAA) in humans.

Stable isotope labeled plant protein in the food matrix labels the IAA following the preparation and ingestion. Further, their appearance in the blood gives a unique bioavailability measurement. Use of 13C labeled reference protein, such as casein, or 13C-labeled free amino acids along with labeled test meal, gives a direct measure of the digestion/availability of the protein under testing. Therefore, the present study aim is to utilize non-invasive, precise, fast throughput methods to measure digestibility and utilization of specific plant nutrients, specifically proteins/ amino acids; focusing on legume-based food products, i.e., chickpea and yellow pea, as it is critical to evaluate the digestion and absorption of dietary amino acids from these products. This is particularly important for lysine (which is limiting in the target population’s diets) and methionine (which is potentially limiting in legume protein), and important because the target group could have environmental enteric dysfunction, which could limit digestibility and absorption. 

While it may seem that protein digestibility is simply the oro-fecal balance of ingested protein, fecal protein is largely microbial protein and compositionally bears no resemblance to the array of dietary amino acids remaining undigested at the end of the ileum. Accordingly, digestibility determined at the ileal level, as an oro-ileal balance, is critical for determining amino acid losses of both dietary and endogenous origin. However this is virtually impossible to measure non-invasively in healthy human subjects. Therefore, there is a need to evaluate the term digestibility by using stable isotopically labeled techniques which employs the use of labeled protein in food based matrix.