{"id":15329,"date":"2026-05-20T11:49:06","date_gmt":"2026-05-20T11:49:06","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/yijun-li\/"},"modified":"2026-05-20T11:49:14","modified_gmt":"2026-05-20T11:49:14","slug":"yijun-li","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/yijun-li\/","title":{"rendered":"Yijun Li"},"content":{"rendered":"","protected":true},"excerpt":{"rendered":"","protected":true},"author":7,"featured_media":15330,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-15329","us_portfolio","type-us_portfolio","status-publish","post-password-required","hentry","us_portfolio_category-new-template"],"acf":{"naam_van_het_proefschift":"Optimizing food supply for nutrition and environmental sustainability","samenvatting":"Het wereldwijde voedselsysteem staat voor uitdagingen op het gebied van zowel voeding als ecologische duurzaamheid, hoewel er regionale verschillen bestaan. Er zijn verschillende strategie\u00ebn voorgesteld om deze uitdagingen aan te pakken, waaronder de herverdeling van landbouwareaal, mengteelt, het verminderen van voedselverlies en -verspilling, en dieetveranderingen. Het implementeren van deze strategie\u00ebn vereist echter een afweging van lokale omstandigheden zoals land- en watervoorraden, populatiekenmerken en de voedingsstatus van de bevolking. Een toegenomen gebruik van plantaardig voedsel, als gedeeltelijke vervanging van dierlijk voedsel, heeft het potentieel om bij te dragen aan betere gezondheids- en milieuresultaten. Daarom onderzoekt dit proefschrift het potentieel van plantaardige voedingsmiddelen om de aanvoer van voedingsstoffen te verbeteren en de negatieve milieueffecten te verminderen met strategie\u00ebn die zijn afgestemd op lokale omstandigheden. Dit proefschrift richt zich voornamelijk op China, gezien het grote aandeel in de wereldbevolking en de belangrijke rol in de wereldwijde voedselproductie, handel en consumptie.\n\nHoofdstuk 1 schetst de huidige uitdagingen op het gebied van voeding en milieu in China. Vanuit voedingsoogpunt omvatten deze onevenwichtige di\u00ebten, gekenmerkt door een lage inname van voedselgroepen zoals volkorenproducten, bonen en noten in vergelijking met aanbevelingen, en een hoge inname van geraffineerde granen en rood vlees. Micronutri\u00ebntentekorten werden gerapporteerd voor stoffen zoals calcium, vitamine A en D, riboflavine, seleen, ijzer en zink. Eiwit wordt als essentieel macronutri\u00ebnt benadrukt in de Chinese voedingsplannen, die het belang onderstrepen van het verkennen van strategie\u00ebn om de aanvoer van hoogwaardige plantaardige eiwitten te verhogen. Vanuit milieuoogpunt overschreed de voedselproductie in China in 2011 al verschillende nationale duurzaamheidsgrenzen, en zonder verzachting zouden de grenzen voor water, land, stikstof, fosforemissies en broeikasgassen (GHG) tegen 2030 worden overschreden. Deze uitdagingen onderstrepen de noodzaak om strategie\u00ebn te onderzoeken voor het verbeteren van de aanvoer van voedingsstoffen op een duurzame en diverse manier, wat het algemene doel van dit proefschrift is.\n\nHoofdstuk 2 bespreekt de belangrijkste uitdagingen en mogelijke oplossingen in Aziatische agro-voedingssystemen, gevolgd door drie casestudy's (\u00e9\u00e9n in China) over ge\u00efntegreerde interventies. Een belangrijke uitdaging in de voedselproductie was het balanceren van productiviteit met duurzaamheid op lange termijn. Oplossingen zijn onder meer het diversifi\u00ebren van teeltsystemen en het bevorderen van technologie-adoptie onder boeren. Latere stadia in de keten, zoals opslag en verwerking, waren gericht op het minimaliseren van verliezen en het verhogen van de kwaliteit. Voedselomgevingen moeten beschikbaarheid, toegankelijkheid en betaalbaarheid van voedzame producten waarborgen. Casestudy's in India, China en Singapore lieten zien hoe succesvolle interventies meerdere fasen van de keten kunnen beslaan, waarbij geco\u00f6rdineerde actie tussen sectoren essentieel is.\n\nHoofdstuk 3 onderzocht de rol van plantaardige voedselvoorziening om te voldoen aan de behoeften aan energie en 17 voedingsstoffen voor de Chinese bevolking. De dekking (aanbod\/vraag ratio) en brondiversiteit werden gebruikt om de voortgang te volgen. Resultaten toonden aan dat de dekking van calcium en seleen laag was, en die van riboflavine en vitamine A gemiddeld. Scenario-analyses toonden aan dat het halveren van voedselverlies en -verspilling, het verhogen van volkorengebruik en het matigen van de inname van rood vlees de dekking van alle voedingsstoffen met 8-44% verbeterde ten opzichte van de nulmeting. Het herbestemmen van gewassen van veevoer naar directe menselijke consumptie resulteerde in zelfvoorziening voor energie en 14 voedingsstoffen.\n\nOnderbenutte granen en bonen (UCB's) zijn meer nutri\u00ebntendicht en vereisen minder middelen dan rijst en tarwe. Hoofdstuk 4 onderzocht in hoeverre de voedingsstoffenvoorziening en milieuduurzaamheid in China verbeterd kunnen worden door landbouwareaal te verplaatsen van rijst en tarwe naar UCB's. Deze gecombineerde strategie verhoogde de gemiddelde aanvoer van micronutri\u00ebnten met 12-82%, verhoogde de eiwitvoorziening met 7% en verminderde het waterverbruik en de broeikasgasemissies met 11-12%, terwijl de energievoorziening gehandhaafd bleef.\n\nHoofdstuk 5 verkende manieren om het aanbod van benutbaar eiwit (utilizable protein) te verhogen, waarbij rekening wordt gehouden met eiwitkwaliteit. Resultaten tonen aan dat het gemiddelde aanbod van benutbaar plantaardig eiwit met 50% verhoogd kon worden door de uitbreiding van sojabonen- en sorghumarealen en de implementatie van ma\u00efs\/soja-mengteelt in 22 provincies. Dit verhoogde ook het aanbod van voedingsvezels en vijf micronutri\u00ebnten met 13-80%, terwijl de nationale sojaproductie met 84% steeg.\n\nTen slotte vatte hoofdstuk 6 de bevindingen samen. Het toonde aan hoe herverdeling van areaal, mengteelt, vermindering van voedselverlies en dieetverschuivingen de aanvoer van voedingsstoffen kunnen verhogen en de milieimpact kunnen verlagen. De thesis benadrukt het belang van het integreren van herverdelingsanalyses in een supply-chain kader en het rekening houden met de biobeschikbaarheid van voedingsstoffen. Concluderend stelt het proefschrift dat deze strategie\u00ebn een aanzienlijk potentieel hebben om de voedings- en milieuresultaten in China te verbeteren, mits er sprake is van een ge\u00efntegreerde aanpak.","summary":"The global food system exhibits challenges in both nutrition and environmental sustainability, although regional differences exist. Various strategies have been proposed to address these challenges, including crop area reallocation, intercropping, reducing food loss and waste, and dietary shifts. However, implementing these strategies requires the consideration of local conditions such as land and water resources, population characteristics, and nutrient status of the population. An increased use of plant-based foods, in partial substitution of animal-based foods, has the potential to contribute to better health and environmental outcomes. Therefore, this thesis explores the potential of plant-based foods to enhance nutrient supply and reduce environmental externalities with strategies tailored to local conditions. This thesis focused mainly on China, given its large share of the global population and its important role in global food production, trade, and consumption.\n\nChapter 1 outlined the current nutrition and environmental challenges in China. From the nutrition perspective, these included imbalanced diets, characterized by low intake of food from food groups such as whole grains, beans, and nuts relative to recommendations, and high intake of refined grains and red meat. Micronutrient deficiencies were reported for nutrients such as calcium, vitamins A and D, riboflavin, selenium, iron, and zinc. As an essential macronutrient, protein is emphasized in China\u2019s nutrition plans, which highlight exploring potential strategies to increase the supply of high-quality plant protein. From the environmental perspective, food production in China in 2011 already exceeded several national sustainability boundaries, and without mitigation, boundaries for water, land, nitrogen, phosphorus emissions, and greenhouse gas (GHG) emissions were projected to be exceeded by 2030. These challenges underscore the need to explore potential strategies for enhancing nutrient supply in a sustainable and diverse way, offering insights into options supporting healthy diets and promoting environmental sustainability, which is the overall aim of this thesis.\n\nChapter 2 reviewed the major challenges and potential solutions in Asian agri-food systems for improving nutrition and environmental sustainability, followed by three case studies (one in China) that report on implemented integrated interventions. A key challenge in food production was balancing productivity (both in quantity and quality) with long-term sustainability. Solutions for this challenge could be diversifying cropping systems and adopting participatory approaches to promote technology adoption among farmers. Downstream stages, such as storage, distribution, and processing, aimed to minimize quantitative losses and enhance quality (through processing and fortification) while keeping environmental and economic costs as low as possible. Food environments should be created to ensure availability, accessibility, affordability, and appeal for diverse and nutritious foods, and provide clear information to encourage healthy dietary choices. Finally, consumers need information and incentives to make healthy diet choices and to avoid waste. A case study in India showed possible subsidy schemes to incentivize farmers to shift from one crop to another, along with information interventions to promote consumption of the crops encouraged for growing. A case study in China demonstrated how e-commerce platforms, in collaboration with local farmers and enterprises, connected rural production to broader markets and increased farmers\u2019 incomes. A case study in Singapore highlighted that whole-grain consumption can be promoted through information interventions for consumers (e.g., media campaigns and regulated health-claim labeling), along with aligned actions among government agencies, the processing industry, and retailers. Together, these case studies exemplified how successful interventions may span multiple stages along the food supply chain, highlighting the importance of cross-sector coordinated adjustments to transform food systems towards more sustainable outcomes.\n\nChapter 3 explored the role and potential to improve plant-based food supply to sufficiently and diversely meet nutrient intake needs for dietary energy and 17 nutrients for the Chinese population. Coverage (supply\/demand ratio) and source diversity (exponentiated Shannon entropy), were used to assess and track progress in improving and diversifying nutrient supply from plant-based foods. We tracked the progress of coverage and source diversity for each nutrient from plant-based foods during 1997\u20132018, and assessed coverage and source diversity for each nutrient from plant-based and animal-based foods (the latter treated as one source) in 2018, serving as a baseline scenario. Results showed that the baseline coverages of calcium and selenium were low, and those of riboflavin and vitamin A were medium, while the other 13 nutrients and dietary energy showed high coverage. Source diversity of these nutrients ranged from 5 to 16. The temporal trend (1997\u20132018) showed that the improvement was minimal for nutrients with low and medium coverage. Scenario analyses showed that reducing food loss and waste, increasing whole-grain use, and moderating red meat intake increased coverage of all nutrients by 8\u201344% relative to the baseline. Repurposing crop products from feed and non-food uses to direct human consumption resulted in self-sufficiency for energy and 14 nutrients, substantially increased the coverage of dietary energy and multiple nutrients, thus enabling greater contribution from nutrient-dense crops with lower yields and lower environmental impact than major crops. Moreover, the results highlight the need for more up-to-date, comprehensive micronutrient status evidence to understand the consequences of current food systems and to guide policies for food-system transformation towards better nutrition and environmental outcomes.\n\nThe so-called underutilized cereals and beans (UCBs) are (pseudo-)cereals and beans with smaller cultivated area than the major staples rice and wheat, but are more nutrient-dense and require less resource inputs (e.g., water, fertilizer). Yet, on average, they have lower yields. Chapter 4 explored to what extent the nutrient supply to the population and the environmental sustainability of crop production in China may be improved by reallocating cultivated area from rice and wheat to UCBs, in combination with an increased use of unrefined rice and wheat. This combined strategy increased the average per capita supply of micronutrients (iron, thiamin, riboflavin, calcium, and zinc) and dietary fiber by 12\u201382% across provinces, raised protein supply by 7%, and reduced total weighted water use and GHG emissions by 11\u201312%, while maintaining dietary energy supply. These improvements required expanding the cultivated area of sorghum (+5.5 Mha), millet (+2.5 Mha), beans (+1.4 Mha), and oats (+0.2 Mha), while reducing rice area by 7.9 Mha (26% of the current total) and wheat area by 1.7 Mha at the national level. For consumers, the combined strategy supported a wide adoption of healthier diets. The supply of UCBs for food consumption increased from 7 to 73 g capita\u22121 day\u22121, along with higher supply of brown rice and whole wheat flour and lower supply of refined rice and wheat products.\n\nThe potential of UCBs to improve nutrient supply and environmental sustainability highlights the need to reassess their value beyond calorie production by accounting for their health and environmental benefits. Such an assessment can inform the design of subsidy schemes that incentivize producers to shift from major staples to more nutrient-dense crops. It is also important to integrate the shift in production with consumption-side interventions that encourage dietary shifts.\n\nChapters 3 and 4 analyzed crude protein supply (total protein quantity). However, protein quality is a crucial factor to consider when analyzing protein adequacy or comparing animal and plant protein, because maximizing crude protein supply for food consumption does not necessarily increase the amount of protein the human body can use. Chapter 5 explored ways to increase the supply of utilizable protein, which is an indicator evaluated as crude protein adjusted for protein quality. This chapter explored how reallocating areas among crops and expanding maize\/soybean intercropping can increase utilizable protein supply without compromising other nutritional or environmental indicators. It considered seven (pseudo-)cereals (rice, wheat, maize, millet, sorghum, oats, buckwheat) and three bean species (soybean, mung bean, adzuki bean). Results show that the average per capita utilizable protein supply could be increased by 50% relative to the 2022 baseline by expanding sole-cropped soybean and sorghum areas and implementing maize\/soybean intercropping in 22 out of 31 provinces, while reducing the cultivated area of rice (1.1 Mha), wheat (0.7 Mha), and some of the considered minor crops. The supply of dietary fiber and five micronutrients (thiamin, riboflavin, calcium, iron, and zinc) was increased by 13%\u201380%, and national soybean production rose by 84% compared to the baseline. The findings highlight the importance of accounting for protein quality when assessing protein supply. Furthermore, area reallocation among crops and expansion of maize\/soybean intercropping are effective in increasing utilizable protein supply and micronutrient supply, and can contribute to soybean self-sufficiency in China.\n\nFinally, Chapter 6 synthesized findings from Chapters 2\u20135 to show how area reallocation, intercropping, reducing food loss and waste, and dietary shifts can increase nutrient supply and lower environmental impact. I discussed how this thesis had broader scientific implications beyond China and policy implications for China. From the scientific perspective, I articulate the potential of further research to embed area reallocation analysis in a supply-chain framework because changes at one stage may affect the entire food supply chain and food system. I note the usefulness of using the area reallocation approach to determine how much cultivated area should be allocated to intercropping, which crop combinations and which intercropping designs to adopt to meet specific goals (e.g., maximizing utilizable protein supply) under certain conditions (e.g., water availability). I show how linking evidence of nutrient supply, nutrient intake, and nutrient status can help identify nutrient gaps, exploring potential strategies to narrow the gaps. The chapter further highlights the need to critically incorporate the bioavailability of nutrients when exploring alternative food systems for better human nutrition.\n\nIn conclusion, this thesis evaluated strategies to increase nutrient supply and reduce environmental impact, with an emphasis on the Chinese context. It explored solutions for area reallocation and expansion of maize\/soybean intercropping, given provincial and national resource constraints, and quantified the overall impact of reducing food loss and waste, using more whole grains, reducing red meat intake, and repurposing non-food uses to direct food consumption. Results showed that these strategies have substantial potential to improve nutritional and environmental outcomes in China, while realizing the potential requires integrated approaches and aligned actions from cultivation all the way to consumption. The thesis proposed several approaches, including analyzing food system capacity to cover nutrient needs in terms of sufficiency and diversity of supply sources, using a systematic framework to assess the impact of area reallocation, and identifying the optimal scale of intercropping at the provincial level. These approaches can be applied to other countries or regions, aiming to use similar strategies to enhance nutrient supply and reduce environmental externalities.","auteur":"Yijun Li","auteur_slug":"yijun-li","publicatiedatum":"15 juni 2026","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/yijunli?iframe=true","url_download_pdf":"https:\/\/ebook.proefschriftmaken.nl\/download\/87fcaff8-57ce-42a8-a759-d100694500bf\/optimized","url_epub":"","ordernummer":"18757","isbn":"","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":15331,"naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15329","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=15329"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15329\/revisions"}],"predecessor-version":[{"id":15332,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15329\/revisions\/15332"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/15330"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=15329"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=15329"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}