Sustained Trial

What is good for the planet is often good for our health. The Sustained study is testing out a new approach to helping people make more sustainable and healthier choices when shopping for groceries online.

We are doing this using a browser extension. The browser extension was developed by a company called Sustained, who work with food industries to design and manufacture eco-friendly products. If you would like to know more about the research design of this study, Find out more about the research design of this study.

The study is led by researchers at the University of Warwick and Queen Mary University of London. It has been approved by the University of Warwick's Humanities and Social Science Research Ethics Committee (you can see the approval here).

This study is part of a bigger group of studies called the SALIENT food trials, which are led by Professor Peter Scarborough from the University of Oxford and Professor Martin White from the University of Cambridge. The SALIENT food trials are funded by the UK government through the Economic and Social Research Council (ESRC).

Study partners include:

Eco-labels provide easy-to-interpret ratings (scores) based on the environmental impact of food products, helping you make informed decisions by considering the environmental impact of food items.

How do we score food items?  

Products are given an overall score of either A, B, C, D, E, F, or G.  Like a grade (with A being the best, and G the worst).

A lot of work goes into giving food products a sustainability score. This is how we work it out:

Scoring of ingredients:  

Some food products, like fruit and vegetables, only have one ingredient. Other food products can be made up of different ingredients, sometimes lots of ingredients. To give an overall score to a product, we need to look at each ingredient to see how it impacts the environment. There are 16 categories we examine for every single ingredient in every single product within a large database. You can click here to find out what each of these categories means.

Scoring of products:  

Each food product’s impact is calculated using the scores from the ingredients it contains, adjusted by weight. Let’s look at an example together: For Tesco 2 Giant Yorkshire Puddings 220G the system looks at the listed ingredients and approximates the percentage of the individual ingredients (where all ingredient percentages are not specified). The ingredient is matched with an ingredient from the databases we are using and their impact per kg ingredient is evaluated, resulting in a single score for each.

These scores are calculated by taking the physical impacts of the ingredients in the 16 impact categories, normalised and weighted to be comparable. All the individual impact category scores are then aggregated into the unique score shown below. In this case, the following percentages were estimated by the system:

Next, the system takes a weighted average of the ingredients to determine the product’s score. In this case that results in 25.79. Higher scores mean that the product has a bigger environmental impact, while lower scores indicate that the product has more eco-friendly ingredients. Finally, all scores calculated are looked at and divided into equal percentiles for each letter grade between A and G. As this score fell into the 4th percentile, it received the grade ‘D’.

Want to take a closer look at a score?  

If you would like to take a closer look at a particular eco-label score, click on the rating above any food product at tesco.com. This will take you to a more detailed dashboard, giving you a breakdown of how a product is rated (e.g. by clicking on the letter G shown in the screenshot below, you will be able to see the breakdown of the score). From best to worst, it will inform you in which areas the food is sustainable as shown in the picture below. By clicking on the drop-down arrows, you can view the scores and additional information for each of these areas.  If a rating looks suspicious or surprising, please see our FAQs which explain some common misunderstandings and may answer your concerns. If you still think there is something wrong with the rating for a product and you would like to report it, click on the 'Unexpected Grade? Report it now' button as shown in the picture below.

Data will be securely stored on the University of Warwick computers which are all password-protected and will be processed only for scientific analysis. Access to the data will be restricted to the researchers involved in this study and the wider team of investigators in the SALIENT consortium. Summaries of the study findings may be presented at conferences and included in scientific publications. Data will be reviewed after a period of 10 years, in line with the University of Warwick data retention policy.

Please refer to the University of Warwick Research Privacy Notice which is available here Research Privacy Notice (warwick.ac.uk) or by contacting the Legal Compliance Team at GDPR@warwick.ac.uk.