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Bioavailability of Proteins from Plant Based Diets
Closed for proposals
Project Type
Project Code
E43031CRP
2048Approved Date
Status
Start Date
Expected End Date
Completed Date
8 December 2021Participating Countries
Description
Recently, protein quality has emerged as an important health issue, especially in low income countries where plants form the main source of protein in the diet. Protein quality is likely to have an impact on the WHO Global Nutrition Target 2025 of reducing the prevalence of stunting (low height-for-age) in children under 5 years by 40%. Stunting has been shown to reduce capacity for learning in children, and hence productivity in adults. Nutrition underpins sustainable development. Uncertainty over the quality of diet, specifically with reference to its protein quality potentially impacts a nation’s health, economy, agriculture and nutrition security, and hence Sustainable Development Goals (SDGs). In particular SDG 1 – End Poverty in all its forms; SDG 2 – End Hunger, achieve food security, improved nutrition, and sustainable agriculture; SDG 3 – Ensure Healthy lives; SDG 4 – Ensure quality education and learning; SDG 5 – Ensure gender equality and empowerment. Estimates of amino acid digestibility based on analysis of faeces relative to foods ingested do not represent the fraction of amino acid absorbed. Ideally, amino acid bioavailability should be measured from oro-ileal balances (the difference between ingested amino acids and the amino acids leaving the ileum), since absorption occurs only in the small intestine and colonic bacteria can recycle nitrogen. However this is virtually impossible to measure non-invasively in healthy humans. The measurement of intrinsically stable isotope labelled plant protein offers a solution to this problem. Either 13CO2 or 2H2O can be used. 2H2O is economically feasible and appropriate for plant proteins. Indispensable amino acids (IAA) become labelled within the food matrix and following preparation and ingestion of the food, their appearance in the blood gives a unique bioavailability measure. If a labelled test meal is accompanied by a trace quantity of a differently labelled reference protein, such as casein, or single cell proteins, comparative tracer appearance gives a direct measure of digestion/availability of the protein under test. This CRP aims to develop and validate novel, minimally invasive techniques to assess protein digestibility and utilization from plant based diets, as they are consumed by vulnerable populations, in regions habitually relying on plant based diets. A novel approach to assessing protein quality will be developed based on the use of 15N, 13C and/or 2H labelled amino acids or intrinsically-labelled proteins. Intrinsically labelled local varieties of grain legumes will be grown in collaboration with local agriculture colleges/institutes.
Objectives
To develop minimally invasive methods to establish quality protein as an important factor of sustainable diet and nutrition for health along the life course.
Specific objectives
To develop a simple method to assess protein quality in vulnerable populations
To develop and characterize a high quality protein that is representative of different diets around the world; to be used as an internal control in the test at all centres
To produce intrinsically stable isotope labelled protein foods to achieve objective 1, including locally available common foods e.g. grain legumes, cereal, milk, eggs, single cell proteins, and fish and flesh foods
To quantify dietary indispensable amino acids made available to the body for optimal growth, development and function along the life course
Impact
The CRP generated new information on indispensable amino acid digestion from diverse pulses consumed in Africa, Asia and Latin America and the Caribbean. This information is based on a new index, the Digestible Indispensable Amino Acid Score, that has been recommended by the FAO since 2013 for more accurate assessment of protein quality. The results have already been widely shared through peer reviewed publications. In some cases the results are already applied to inform dietary recommendations.
For example, Shivakumar and co-workers (2019) estimated true ileal IAA digestibility of 4 foods commonly consumed in complementary diets in India, showing that the digestibility of key IAA such as methionine was lower than may have been assumed. They also showed that the DIAAS was associated with stunting and recommended the inclusion of animal source foods (ASF) in children's diets to improve growth. Two further publications are in preparation including a Human Health Series on the Dual Isotope Tracer Method. Results published from India are already being considered by policy makers to inform the quality of protein in food subsidies for children.
Capacity building
The CRP fostered both South-South and North-South technology sharing and transfer. For example, researchers from Mahidol University, Thailand, have been supported by experts from the IAEA Collaborating Centre in nutrition, St. John’s Research Institute, Bengaluru, India, to develop analytical capacity in protein digestion assessment. Similarly, Moroccan scientists based at the AFRA Regional Designated Center in nutrition in Rabat benefited from fellowships and technical support from experts based at AgroParisTech, Paris, France and have since set up their own analytical capacity.
Gender balance
The CRP enabled training of women scientists and PhD students. A total of 19 students and technicians (10 women) were trained in both agronomy and nutrition and human health.
Cross-discipline interaction
In each country involved there is now a network of human nutrition and agricultural scientists.
Potential engagement with climate change scientists, agro-economists
With the emerging crisis of climate change and water scarcity, both protein content and yield of plant food protein sources is likely to decrease; it is unknown how protein digestibility will change in these conditions. Opportunity exists in determining the protein content and digestibility of drought-resistant plant varieties. Further, inputting the DIAAS into models of global protein food supply in the context of a growing global population and adverse environmental change is highly imperative.
Potential for cross-agency collaboration through Joint IAEA/FAO Database on Protein Quality of Foods
With the outputs on ileal digestibility of legumes in 7 countries, a detailed description of the protein quality of different legumes by the DIAAS index is now possible. This is the first integrated effort to collate data that will inform the FAO protein quality recommendations for humans. FAO is seeking standardized DIAAS data in humans to inform recommendations for protein requirements for all age groups. Results of this CRP inspired a first of its kind Joint IAEA/FAO Technical Meeting to establish a framework for a global database on protein quality.
International Conferences
1. Some of the results were presented during the IUNS International Congress of Nutrition, December 2022, Tokyo, Japan.
2. Results will be further shared at the planned International Symposium on Dietary Protein and Human Health in September 2023. The IAEA is part of the organizing committee.
Related TC Projects
The CRP inspired a new Asian regional project in the 2022-2023 cycle: RAS6103 ‘Applying Stable Isotope Techniques to Assess Protein Quality of Sustainable Food Sources for the Improvement of Maternal and Child Nutrition’.
Related CRPs
The CRP also inspired an on-going CRP E43036 'Efficacy of Amino Acid Supplementation in Treating Environmental Enteric Dysfunction Among Children at Risk of Malnutrition'.
Relevance
Protein quality has a great importance in meeting the nutritional needs of populations across the developing world throughout the life course, but in particular during pregnancy and early childhood. Protein quality is likely to have an impact on the WHO Global Nutrition Target 2025 of reducing the prevalence of stunting (low height-for-age) in children under 5 years by 40%. Stunting has been shown to reduce the capacity for learning in children, and hence productivity in adults. Nutrition underpins sustainable development. Uncertainty over the quality of diet, specifically with reference to its protein quality potentially impacts a nation’s health, economy, agriculture and nutrition security. Estimates of amino acid digestibility based on analysis of faeces relative to foods ingested do not represent the fraction of amino acid absorbed. Ideally, amino acid bioavailability should be measured from oro-ileal balances (the difference between ingested amino acids and the amino acids leaving the ileum), since absorption occurs only in the small intestine and colonic bacteria can recycle nitrogen. However this is virtually impossible to measure non-invasively in healthy humans. The measurement of intrinsically stable isotope labelled plant protein offers a solution to this problem. Either 13CO2 or 2H2O can be used. 2H2O is economically feasible and appropriate for plant proteins. Indispensable amino acids (IAA) become labelled within the food matrix and following preparation and ingestion of the food, their appearance in the blood gives a unique bioavailability measure. If a labelled test meal is accompanied by a trace quantity of a differently labelled reference protein, such as casein, or single cell proteins, comparative tracer appearance gives a direct measure of digestion/availability of the protein under test. This CRP enabled the development of a novel, minimally invasive technique to assess protein digestibility and utilization from plant based diets, as they are consumed by vulnerable populations, in regions habitually relying on plant based diets.
The CRP brought together crop scientists and nutritionists from 7 developing countries who worked in collaboration and exchanged skills and knowledge with experts from more resource endowed countries to generate new information on the bioavailability of indispensable amino acids (IAA) in pulses consumed across the Asian, African, Latin American and the Caribbean regions. The results generated will in the short run be included in a planned joint FAO/IAEA database on protein quality and will eventually be used to inform future intervention studies aimed to provide the recommended amino acid intake from local plant based foods, i.e., by providing the available IAA supply judged to meet the daily demands for growth and maintenance.
To date 7 publications and 1 conference presentation, and 1 web-article have helped to make the results available worldwide. The method was also highlighted in the Nuclear Technology Review 2020 'New Dual Isotope Tracer Method for Protein Quality Assessment in Humans'. The CRP has inspired two Technical Cooperation projects, 1 regional (RAS6103 Asia) and 1 national (PHI6027 Philippines) project, and 1 CRP E43036. Results from the CRP were presented at the Joint FAO/IAEA Technical Meeting on the Development of a Protein Database and the Way Forward for Reviewing Protein Requirements, held in October 2022 and will be included in the planned database. The results will also be presented at the planned International Symposium on Dietary Protein and Human Health to be held in Utrrecht, The Netherlands in September 2023; IAEA is co-organizing the symposium.