Food Systems and Nutrition Evidence and Gap Map

To address the challenge of malnutrition and food insecurity, decision-makers need to understand what evidence exists on various interventions. 3ie’s first living evidence and gap map (E&GM) includes the largest collection of high-quality research on food systems interventions in low- and middle-income countries. With support from BMZ through GIZ’s “Knowledge for Nutrition” program, we continuously monitor the available evidence and regularly add studies to ensure the E&GM remains a useful and current tool for our users.


Food systems are crucial to achieving most of the 17 Sustainable Development Goals (SDGs), as well as multiple other goals and commitments, such as those on climate change. What we need is science-driven food transformation and research will continue to play a vital role in this. 3ie has been engaging in its ambitious living evidence-mapping process for three years. The project has now been extended for an additional year and will continue through March 2024. Our first living evidence and gap map (E&GM) includes the largest collection of impact evaluations and systematic reviews on food systems interventions in low- and middle-income countries. Our Food Systems and Nutrition Evidence E&GM shows where evidence is available and where new research is needed to fill evidence gaps regarding the impacts of food systems interventions.

Making sense of a vast and growing literature

Our E&GM includes over 2,400 studies and presents a rich body of evidence, including the latest research, in the fast-growing field of food systems impact evaluations. It reports on evidence from all key areas and intervention types and identifies potential primary and synthesis evidence gaps. We regularly publish summaries of how the literature has changed and provide insight into the development of evidence gaps and clusters. We are also leveraging it to produce a series of evidence synthesis products.

In the last two years, since the continuous update process started, we have added 414 impact evaluations and systematic reviews to our already large evidence mapping project (containing 2,035 studies at its launch in January 2021). Although this represents a 20 percent increase, we actually find that the rate of expansion in the evidence base has decreased since 2019. After reviewing the studies added to the map and current development priorities, we determined that none of the previously identified evidence gaps have been filled. We added three additional evidence gaps based on interventions: cold chain initiatives, farm-to-market transport, and food safety regulation. In addition, few high- or medium-confidence systematic reviews have been published, meaning that this evidence base is rapidly becoming out of date.

The map is expanding. We have added a filter for ‘year’ at  the top of the map, interventions and outcomes considering gender transformative approaches. We will also add social protection interventions.  Read the brief, full report, mid-term report and notes on the December 2021, April 2022, August 2022, January 2023, July 2023 and November 2023 updates

Findings from the original map

In the original E&GM (covering January 2000 – September 2020), evaluations disproportionally considered supplement provision (20%); fortification (16%); direct food provision (11%); and peer support and counselling targeting consumer behaviour (7%). No or few evaluations assessed advertising regulations, food waste education programs, food packaging, governmental price manipulations, and interventions supporting women’s decision-making or measured women’s empowerment outcomes.

Latest findings

The map has now been updated in six instances—December 2021 (covering September 2020-June 2021), April 2022 (covering July 2021 – January 2022), August 2022 (covering January – April 2022), January 2023 (covering May 2022 – December 2022), June 2023 (covering January 2023 – April 2023), and November 2023 (covering May 2023-July 2023). We have also published a mid-term report, summarizing the evolution of the evidence base from January 2021 to January 2023.

In this latest update, we added 146 new studies to the map. We see similar intervention trends to the original, but there is a reduction of proportion of studies evaluating supplementation and fortification interventions and an increase in agricultural education and training interventions.  In this update we have expanded the outcome framework by adding gender transformative outcomes. No new studies were included based on this outcome, but 19 already included studies were identified as measuring a gender transformative outcome. 

Studies added to the EGM

*These represent new priority areas identified through our mid-term report

Benefits of a living EGM

Because this is a living evidence-mapping process, as new policy priorities develop in the field, we are able to rapidly identify studies evaluating relevant interventions and make these easily accessible to decision-makers. This ensures that the most up to date evidence is available. We are able to highlight the evolving evidence needs of the field through our regular stocktaking of the distribution of the evidence.

Extending the use of the living EGM

To fill some of the key gaps identified through the mapping process, 3ie produced two additional synthesis products: a rapid evidence assessment on the impact evaluations of women’s empowerment interventions included in the map and a systematic review on the use of fiscal policies to support a healthy diet. These synthesis products were produced in less than half the time of traditional systematic reviews because we were able to leverage the E&GM. 

Evidence on women’s empowerment within the food systems 

Findings: There were ten impact evaluations of interventions to support women’s empowerment within the Food Systems and Nutrition Evidence and Gap Map. Overall, these interventions generally had positive impacts on food security and food affordability and availability. Evidence from qualitative work suggests that women’s empowerment interventions best influenced nutritional outcomes when adopting gender-transformative approaches and addressing gender and social norms.  

Implications: Policy-makers should consider improving women’s social capital so they can better control and decide how to feed their families. Qualitative evidence suggests that multi-component interventions seem to be more sustainable than single-focus interventions, especially when they combine a livelihoods component (asset transfer or financial services) with behavioural change communication. Researchers need to address issues with inconsistent data and reporting, particularly relating to seasonal changes, social norms and time taken between rounds of data collection in order to implement high-quality evaluations. Future studies could further contribute to the evidence base of gender-transformative approaches by carefully considering contextual norms and avoiding stereotyping women into pre-decided roles which may perpetuate social norms. 

Read the Brief

Evidence on taxes and subsidies to support a healthy diet

Findings: We identified 49 impact evaluations and two systematic reviews through an additional systematic search that extended beyond the Food Systems and Nutrition Evidence and Gap Map. Unfortunately, these represented only 24 unique intervention-outcome-population combinations due to the repeated evaluation of the same taxes. We found that taxes on unhealthy foods may decrease the purchases of unhealthy foods, but this effect was driven by a single, high risk of bias study. Impacts on diet, health, and well-being were rarely considered, so conclusions could not be reached. However, we did find evidence that awareness of the health-based justifications for the taxes and the health consequences of consuming such foods may facilitate the impacts of these interventions.  

Implications: Tax and subsidy policies aimed at improving diets should incorporate information campaigns on health benefits and health risks associated with certain food and beverage consumption. For tax policies, exposure to health information may amplify the signalling effects of taxes and reduce avoidance behaviours, such as cross-border shopping. Future evaluations of fiscal policies should diversify data sources to better understand the impact on diet and health outcomes. Future research should also use evaluation design strategies that account for confounding and independence from other programs or events that may occur during the implementation period. 

Read the Brief

Watch our webinar on ‘Filling knowledge gaps to transform the food system’ which brought together experts from GIZ, EAT Forum, IFPRI, Bill & Melinda Gates Foundation, and Centre for Global Child Health. The panel focused on the experience in navigating the evidence base within the field, the types of evidence needed, and how the research community can better respond to the evidence needs of policymakers and implementers.

The effects of food systems interventions on food security and nutrition outcomes in LMICs

The devastating impacts of malnutrition and food insecurity are well documented. In low- and middle-income countries (L&MICs), constraints and complexities within food systems are significant drivers of these conditions. As a result, there has been a significant global focus on improving food systems to facilitate better food security and nutrition outcomes. The evidence base regarding the impact of interventions within food systems in achieving these aims is massive, but complicated and disorganized, making it difficult for donors, policymakers and practitioners to navigate. 3ie's Evidence Gap Map addresses this challenge.