What did you eat yesterday? The messy science of measuring what we eat

Posted by Dr Kath Roberts, Senior Lecturer in Public Health Nutrition, University of York

Ask anyone what they ate yesterday and you’ll likely get a pause, a guess, and maybe a laugh. That’s the reality nutritional epidemiologists (scientists who study how diet affects people’s health) work with every day. Measuring what people eat sounds straightforward but is surprisingly complex. And yet, understanding dietary intake is central to advancing nutrition science, improving public health, and shaping government dietary guidelines.

Increasingly, attention is turning not just to what people eat, but how well they eat overall. The concept of diet quality, looking at the overall balance, variety, and healthfulness of the diet has become a cornerstone of nutrition research. It also offers a way to bring together fragmented messages about nutrients, food groups, ultra-processed foods and national guidelines into one meaningful measure. But defining and measuring diet quality is just as tricky as tracking individual foods.

This blog reflects on the practical and scientific challenges of defining, collecting, analysing and interpreting dietary data and reflects on how improvements in methods and technology are shaping the future of dietary data.

Why measuring diet is so difficult

Capturing dietary intake data involves a tangle of practical and methodological problems. First, there’s the human element. People often don’t remember exactly what they ate or may selectively forget. This recall bias is especially tricky with foods eaten on the go or in small amounts. Then there’s social desirability bias. People want to give the “right” answers, especially if being questioned by an actual human (as opposed to filling out a diary or survey). So while a few honest folk might confess to having a chocolate bar for breakfast and a midweek takeaway, many prefer to report kale and quinoa - or at least a committed adherence to the holy ‘five-a-day’ grail. The result? A gap between what people say they eat and reality.

Then there’s the issue of burden. Some methods, like weighed food diaries, ask a lot of participants. Accurately weighing and logging every bite is time-consuming and often tedious. It may even change behaviour just to make recording easier. My own experience some years ago with logging foods through a free and widely used app was that it made me lean towards buying and consuming processed foods that I could just scan the barcode of, rather than cooking from scratch or shoving whatever was in the fridge onto a plate as I usually would. Other methods like food frequency questionnaires (FFQs) and 24-hour recalls try to reduce this burden but come with their own compromises.

Tools of the trade: strengths, weaknesses, and trade-offs

FFQs remain popular in large epidemiological studies because they’re cost-effective and can capture habitual intake over time. However, they rely on memory and a fixed list of foods that might not reflect cultural or personal variation, only capturing, by design, data on what they ask about. 24-hour recalls offer more flexibility and less reliance on long-term memory, especially when conducted with structured prompts like the USDA's multiple-pass method. But they only capture a snapshot in time and one day rarely reflects the whole story. Diaries, whether weighed or estimated, provide rich detail but at a cost. They demand motivation, literacy, and a willingness to record every meal, snack, and nibble without altering usual habits.

Brief screeners, like the US Healthy Eating Index or dietary diversity scores, offer pragmatic options for surveys or interventions. They’re easier to administer and analyse, but they tend to gloss over the nuance of full dietary patterns. And they still face questions of sensitivity and specificity - are they really measuring what matters most for health?

So what is a healthy diet anyway?

Amidst the tangle of dietary data collection challenges, there is the important question of ‘what is a healthy diet’? This is where the idea of diet quality comes in. Rather than counting single nutrients or fixating on particular foods or food groups, diet quality looks at the whole picture: how balanced, varied, and aligned with health guidelines someone’s overall eating pattern is. It’s become a cornerstone of nutrition science and epidemiology, but it’s surprisingly hard to pin down and turn into a clear, usable measure for research.

This also matters for public health messaging. People are bombarded with a range of different messages. We have the NHS Eatwell Guide, the High Fat Salt Sugar (HFSS) advertising restrictions, front-of-pack nutrition labelling, SACN Dietary Reference Values, rising concerns about ‘ultra-processed foods’ - and these don’t always line up. Each of these frameworks is based on different criteria and assumptions; food-based, nutrient-based, processing-based - which can send mixed messages and make public health advice feel inconsistent or overwhelming. Without a consistent definition of what a ‘healthy diet’ looks like, it’s easy to get confused.

That’s why the idea of diet quality is so powerful: it can provide a coherent construct that integrates these strands and translates complex nutritional science into something more intuitive and holistic. But the reality of defining and measuring diet quality is messy. Efforts like the UK-DQQ show promise, offering a simple, food-based screener aligned with national guidance, derived from empirical dietary patterns and validated against both biomarkers (e.g. blood and urine) and nutrient intakes. But even this needs updating as dietary trends evolve and must be validated in diverse population groups.

The trouble with comparing apples to oranges (or diet scores to diet scores)

No universal agreement on how to define a ‘healthy diet’ contributes to variation between studies, making it hard to compare results or synthesise evidence. Some researchers focus on diet quality scores (like HEI), others on dietary diversity, others on adherence to national guidelines or cultural patterns like the Mediterranean diet. These varied definitions mean that two studies can report on ‘diet quality’ but be talking about quite different things.

The Mediterranean Diet Index and its adaptations, such as the relative Mediterranean Diet Score or alternate Mediterranean Diet Score, are widely used in Europe. These scores capture core elements of Mediterranean dietary patterns: a lot of vegetables, pulses, fruits, nuts, olive oil and fish; moderate alcohol drinking; and low amount of red meat and dairy. In countries like Spain, Italy and Greece, these tools have helped characterise regional diets and assess traditional dietary patterns in relation to cardiovascular disease, cancer, and overall death rate.

European examples such as the EPIC cohort (European Prospective Investigation into Cancer and Nutrition) show how differing dietary patterns and assessment methods between countries can complicate analyses. EPIC responded by conducting extra studies to adjust for differences in how diets were measured across countries.

The cost of precision

Gold-standard methods like weighed food diaries or duplicate meals offer unmatched detail, but they’re expensive, burdensome, and often impractical for large groups. Even with trained coders and food composition databases, analysis is slow and complex. Participants may forget to record, misestimate, or change how they eat.

And food diaries only capture a few days raising the question: are those days typical? People might eat differently on weekends, holidays, or when they’re sick. So we need multiple days, and sometimes biomarkers or repeat measures, to estimate what is usual. That’s time and resource intensive. And even then, we must account for people who report eating less than they actually do.

In the UK, the National Diet and Nutrition Survey switched from 7-day weighed diaries to 4-day estimated ones, to computerised 24 hour recall methods. These changes reflect the challenge of balancing accuracy, rigour, realism and resource constraints.

From challenge to opportunity: smarter tools, better insight

The good news? We’re getting better. Digital tools like Intake24, MyFood24 and ASA24 allow self-administered, online 24 hour recalls with built-in prompts, portion images, and food databases. These tools reduce burden and standardise data collection. AI is also being explored for recognising foods from images, helping reduce reliance on memory and self-reporting.

Dietary pattern analysis is also on the rise. Rather than fixating on individual nutrients, researchers are looking at how foods cluster together using tools like principal component analysis. These approaches acknowledge that we eat meals, not molecules and that whole-diet patterns may offer a more stable and interpretable link to people’s health.

What now?

Dietary data collection isn’t perfect and may never be. But it’s getting better. By balancing scientific rigour with practical constraints, and by using emerging technologies and analytic strategies, researchers can produce meaningful insights. Whether it’s via smarter recalls, better biomarkers, or dietary pattern-based analysis, the goal is the same: to understand how what we eat affects our health and how we live. That journey starts with listening carefully, thoughtfully, and with an appreciation for just how tricky it is to answer the simple question: “What did you eat yesterday?”

So the next time you try to recall what you ate yesterday, remember you're not alone - even science is still figuring it out!

Cookies, coffee and co-production during Covid

Posted by Emma Adams, Fuse/NIHR School for Public Health Research (SPHR) Pre-doctoral Fellow at Newcastle University, in collaboration with Experts by Experience from Fulfilling Lives Newcastle Gateshead and #HealthNow Newcastle

Photo taken by Jeff Parker (one of the individuals with lived experience involved in our
co-production) of the masks he made for each of us at our first face-to-face meeting. 

COVID-19, has forced all researchers to re-think engagement and how we work with people with lived experience. I like many, have been navigating how best to do this within my study that aims to explore and understand access to community-based mental health and substance use support in Newcastle and Gateshead for those experiencing homelessness during the pandemic.

Since March 2020 I have been collaborating with five people with personal experience of homelessness, mental health, and/or substance use to co-produce the analysis for this study. During that time we have discovered a very helpful approach (albeit with an imposing name) - Interpretative Phenomenological Analysis.

Here comes the science…

This approach was very reflective and recognised that we were trying to understand how our participants made sense of what had happened to them. We wrote exploratory comments to reflect on the word-for-word text from interviews and then used both to develop themes. This approach lent itself really well to our analysis, as we found it was less rigid than other coding-based approaches (such as thematic analysis) and had more opportunity for reflection. 

The saying ‘no two things are alike’ describes how we ran our co-production meetings given COVID-19 restrictions. We sent out printed packages with anonymised transcripts for comments, held Zoom meetings to discuss our comments and thoughts, hosted in-person meetings with sticky notes and marker pens to develop themes and unpick key ideas, and used physical and virtual highlighters to identify our top quotes. Accompanied with a healthy amount of coffee, baked treats, and fruit, we set our sights on trying to understand our data. We broke down each analysis into three sessions, with the first session focussed on reviewing the transcripts and writing comments, the second focussed on developing some initial themes, and the third focussed on identifying and refining all the themes and key quotes.

Friendship, findings and reflections

We are now starting to share initial findings and determine creative ways to present the information. Having built a strong friendship, we reflected on how much we enjoyed the collaborative co-production experience, despite the circumstances created by COVID. We also reflected that not all co-production is positive. Here we share a few thoughts from the experience.

Why did you become involved in the study?
Everyone in our group felt motivated by the opportunity to have their voices heard and make a difference.

"Because I am interested in how the pandemic has affected people and am a member of the Experts by Experience and would like to change things for the better" – Joanne

"I wanted to do a different sort of user health research having done some last year in Newcastle for Crisis and Groundswell. Getting involved in analysing the anonymised data was a fantastic opportunity for myself" – Tony

What did you enjoy and learn?
Everyone enjoyed being involved as the research continued to grow and their continuous involvement meant we could develop friendships.

"Actually being involved from start to finish, Emma baking" – Jeff

"Analysing some of the data and the group! I feel new friendships have been made" – Fiona

 Although different learnings were shared, it was clear that everyone enjoyed working in a team to try out new things and have a ‘behind the scenes’ peak into doing research.

"One day I would really like to do more of this work in a permanent position as part of my continuing personal development. So it was very nice to get the opportunity to find out what this sort of work entailed and whether or not I would enjoy doing it too" – Tony

"Co-production can really work if it's formulated with an organic and lived experience perspective at the heart of the study, the information gathered was not lost in translation and the language from participants' interview was not tampered with" – Des

What did you find challenging and wish researchers knew?
Forcing ourselves to think about some of the things we all found challenging, we realised it is important to touch base with people involved in co-production to understand what they are struggling with and how they can be better supported.

"Biggest problem I have is getting to a venue, I have anxiety issues travelling by bus" – Jeff

"Emma would send me a gentle reminder a few days before work was due and it would spur me to either start, or finish off and get the work sent in. This really helped me" – Fiona

What would you say to a friend about getting involved in research?
Across the board, everyone said they want to continue to be involved in research projects and would encourage friends to do so.

"At first it might fly over the top of your head, but give it time and you will learn things you never knew you were capable of" – Joanne

"Go for it, maybe you can help affect change that will help others who have been through what you have. Plus, you’ll make some new friends and may enjoy yourself too" – Jeff

What are you most excited about?
When asked about what they were most looking forward to and anything else they wanted to share, responses ranged from gaining specific experience, to celebrating successes.

"It made a nice change to be more involved and now I’m doing more research with Crisis its helped me to help them shape how it can be done and how sense making is carried out" – Jeff

"The biggest rush of the project was to receive an email from the Lancet after we submitted a piece on the work. If it gets published, I’m throwing a party" – Fiona

"Emma has kept us updated throughout and involvement moving forward looks bright … and on the back of this there is confidence to come back to the university and vice versa in other research projects" – Des

Lessons learned from a researcher perspective

The depth and richness gained through co-producing my analysis is something I could have never done on my own. I learned that it is okay to admit when you are feeling a bit lost about the best approach, as that allows for an open dialogue to determine what can be done to make things better. Through our co-production, I realised how to make findings more accessible and engaging for everyone. The pandemic has meant that we have all missed out on in-person contact. Listening to our group I was shocked and humbled by how much the little touches mattered; well-timed cookies or an invite for a coffee chat can make a big difference. These small touches allowed me to develop relationships with everyone and have frank and honest conversations. From this experience, I have learned that you do not need to wait until you have findings to make a difference, rather you have a chance through co-production to make lasting impacts across the span of your research project.

Emma's study 'Exploring and understanding access to community-based mental health and addiction services in Newcastle and Gateshead' is NIHR School for Public Health Research (SPHR) ResNet funded.

This project is funded by/ supported by the National Institute for Health Research (NIHR) School for Public Health Research (Grant Reference Number PD-SPH-2015-10025). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.

Find the gap: where is the healthy, enjoyable human body in policy?

Posted by Rachel Kurtz, PhD researcher at Durham University

Balancing varied and sometimes conflicting priorities within a large geographical area and between multiple departments is not a job to be envied. Ensuring the detail is suitably deliberated while also holding in mind how a policy affects other interests must be attempted but cannot possibly be achieved to perfection. My role on behalf of County Durham Sport was much easier. Over three weeks in June, I reviewed Durham County Council documents and the priorities of the Area Action Partnerships (AAPs) to identify areas of local strategy that did (or did not) address the issues of physical inactivity and the climate emergency. As an environmentally-informed, lifelong dancer-turned-researcher, I simply had to view the documents from two perspectives in which I am already personally invested and consider possible changes. Some interesting things emerged.

As you might expect, topics are viewed through whatever lens highlights policy concerns in that area. For example, the County Durham Plan understands physical activity functionally, through land use, waste, and movement of people, advocating for active travel (walking, cycling etc.) and providing and improving recreational areas. Meanwhile, the Joint Health and Wellbeing Strategy considers the environment as either beneficial or detrimental to public health, e.g. air quality. Thinking that is limited by departmental divisions can make it difficult to link overlapping policy areas. Consequently, councils are attempting to increase communication and collaboration by forming multi-disciplinary teams to create joint policy and consider issues from multiple perspectives. The County Durham Health and Wellbeing Board (author of the previously mentioned strategy) is one such team. This ongoing shift towards a collaborative approach is already countering siloed thinking and Durham County Council is taking a systems perspective through its work in Mental Health, from its strategic partnership both within and outside the council to delivery vehicles like the AAPs (which give local people and organisations a say on how services are provided). Nonetheless, a change of perspective inevitably exposes assumptions and raises new challenges, and this was no exception.

Encouragingly, some of the documents reviewed, such as the 2018 Open Space Needs Assessment, comprehensively address both focus areas, however in most cases the environment features more prominently than physical activity. A Physical Activity Strategy is still being developed, therefore gaps in this area might be expected and indeed in many cases the human body was entirely absent from policy. However, what was most noticeable was the underlying attitude where physicality was mentioned. Almost none of the policy documents feature the healthy, enjoyable human body. To cite a specific example: while addressing a rising mental health crisis, the Health and Wellbeing Strategy implicitly regards bodies as problems to be solved. This is particularly noticeable in the section on older people who are seen as frail and in need of preventative and remedial support. The framing of the strategy is already being addressed in this case but overall, any focus on the impact of health and wealth inequalities on the body tends to see physical inactivity as a problem rather than an opportunity. There were exceptions at delivery level (e.g. the Healthy Weight Action Plan and some AAP interventions, both of which are very much about enrichment) but at the strategic level, bodies are overwhelmingly framed as problematic. This is true even where you might expect an enrichment perspective such as the Children and Young People’s Strategy and Strategic Walking and Cycling Delivery Plan.

As a dancer and embodiment researcher this outlook is all too familiar, and I understand it as cultural rather than a failing of the council. In the main bodies are accommodated, objectified and treated as problems to be solved, while the sensual, experiencing body is largely ignored. Unfortunately, when we take this deficit perspective, we lose important, humanising opportunities for productive fun. Policy could be very influential in this respect. If we choose instead the underpinning belief that bodies are an incredible gift through which we explore and enjoy an endlessly engaging world, we automatically find more playful and interesting solutions. Suddenly new possibilities abound, like generating power from playground equipment or a dancefloor made with kinetic tiles. When we remember our sense of fun, urban environments become play spaces for curious bodies. Street furniture is for parkour, roller blading or skateboarding as well as resting. Outdoor games and gyms spill out of parks and line the route of our walking commute. Community growing spaces (already a popular solution to poor diet, food miles, climate change preparedness, physical inactivity, social isolation and low income) are no longer confined to small allotment plots but proliferate around the city alongside the begonias, encouraging healthy eating and a pedestrian habit.

Negotiating such varied needs and uses does of course require extensive consultation and consideration, which again highlights the importance of a partnership approach through which all voices are heard, but as I said at the outset, policy making is inevitably a difficult job. The bonus of reframing in this way is that by using strategies that are intentionally enjoyable rather than those that feel worthy or obligatory, uptake is likely to be far higher and as a result there is a better chance of achieving positive outcomes. Surrounded by the richness of creative human expression and snacking on free, community-grown fruit as we walk, jog, cycle or even dance our way to work and school, why would we choose to drive? 

Images:

1. Photo by Anthony Fomin on Unsplash

2. Photograph 'Exercise Machines' (2103264189_e26de7ba22_z) by Catherine via Flickr © 2007: https://www.flickr.com/photos/30325243@N00/2103264189 (CC BY 2.0) Adapted (cropped)

3. Photo by markusspiske on Pixabay

Struggling to see a way through your data? Try a different lens

Posted by Peter van der Graaf, AskFuse Research Manager / Fuse Knowledge Exchange Broker, Teesside University

“Having trouble analysing your qualitative data? Are you lost in the sheer amount of data you have collected and don’t know where to start?”

This was the strapline of a course at Kings College London last week, called ‘Ethnography Language and Communication’ and a big reason why I attend the summer school. Within my NIHR Fellowship research, I have collected big piles of observation notes, interview transcripts and meeting minutes and struggled to make sense of them. So did the course deliver?

Over five days, we were presented with a range of analytical tools borrowed from linguistics and applied to qualitative data (interview transcripts and video recording of job interviews and classrooms) with an ethnographic lens. In essence, this means trying to understand how meaning is constructed in social interactions by studying text and recordings generated from these interactions in fine detail. First from the perspective of the specific situation in which these texts were constructed, but with an explicit aim to make valid statements about the wider social structures in which these interactions are embedded.

The course leaders* have even come up with a name for this academic discipline: ‘linguistic ethnography’. Linguistic ethnographers acknowledge that texts are representations of social actions and, therefore, that to understand these texts you need to closely investigate the social interactions that produced them.

However, they also explore how these interactions are embedded in institutional contexts and are closely linked to social interactions elsewhere, both in time and location, adding a historic and place perspective. Sociological concepts of power, social class, inequality and identity feature eventually in these analyses but are not presumed and not used in the first instance. The specific context of the social interaction is initially key for understanding what is going on.

The course attracted speakers and participants from across the globe, including the UK, US, China, Spain, Germany, Austria, Belgium, Turkey, Israel and many more. This international gathering aligned nicely with the aims of the course: being highly interactional, working across different contexts with different types of data and approaches coming together to co-create a better understanding of their data.

Although we discussed many theoretical concepts, the course was also practical and gave us the opportunity to experiment with a range of analytical tools (or what Ben Rampton preferred to call ‘sensitizing concepts’): from micro-analysis (a form of Goffmanian conversation analysis: applying a dramaturgical lens (life is a stage!) to data interpretation) to discourse genres featuring The X Factor, multi-modal analysis (looking simultaneously at different modes of communication such as language, gaze and gestures), semiotic landscapes (e.g. how shop signs in neighbourhoods communicate change) and trans-contextual analysis (how text moves and changes across contexts and interactions). If you are confused by the plethora of terms and concepts, you feel exactly as we did during the course!

However, this was also the point: gaining experience of applying a range of tools that overlap or sometimes contrast with our data to find new insights that we wouldn’t otherwise have discovered. If it is helpful, use it; if not, try another tool or a combination of tools. In this sense, the course was very pragmatic. And this also applies to the role of being a linguistic ethnographer. You do not need to do X, Y and Z as a minimum, with a potential dusting of C to call yourself a linguistic ethnographer. Instead, you prescribe to a set of principles about the nature (social interaction), context (multi situational) and structure (institutional framing) of texts and recordings, that help you to choose from and apply an analytical toolkit.

Applying a different lens

Did it help me make more sense of the qualitative data I collected for my research project? No (at least not yet), but the course provided me with a starting point for analysis. It also helped me realise that trying to incorporate and do justice to all the data that I collected is simply not possible. Instead, applying a linguistic ethnographic lens to my data will help me to identify instances of text that signify social interactions that are critical for my understanding. This will ultimately help me to build an argumentative structure for my papers.

I will still need to go through all my qualitative data in detail but have a better sense of how to navigate this now.


*Ben Rampton, Kings College London; Adam Lefstein, Ben-Gurion University of the Negev; Jan Blommaert, University of Tilburg; Jeff Bezemer, University College London; and Julia Snell, University of Leeds

Could collective community power direct future public health research?

Guest post by Liam Spencer, Research Assistant, Institute of Health & Society, Newcastle University

The Tyne & Wear Citizens are a local division of Citizens UK, a community organising group, which comprises of schools, universities, faith groups and charities. The group launched a ‘Commission on Mental Health’, which aimed to map problems, and identify solutions around mental health services in the region. In early 2018, The Tyne & Wear Citizens approached AskFuse [Ed – Fuse’s responsive research and evaluation service] in order to identify researchers to contribute to the analysis and production of their final report, ‘Living Well: Mental Health and Public Life in the North East’.

Through Professor Eileen Kaner (Newcastle University/Fuse), I had previously been involved in another AskFuse-supported project called ‘PROMOTE:NE’, which looked at young people’s mental health across the North East, and we met with Dr Peter van der Graaf and Lesley Haley from AskFuse to discuss this piece of work. Following this, I met with Revd Dr Simon Mason and Dr Joe Barton from the Tyne & Wear Citizens, and they were very happy to have me working with them, with supervisory support from Eileen.

The Commission had collected over 300 individual written ‘testimonies’ from people across the region, who articulated what was good, and what was not so good about mental health services in the region. It was these testimonies, which formed the basis of the Living Well report, and helped shape what the Citizens were asking local politicians and organisations to commit to. Prior to being involved in this piece of work, I had no understanding of what community organising was, and initially it was a challenge to grasp the concept of what the Commission were aiming to achieve, and how I could best contribute to this. In order to gain a better insight, I attended one of the Mental Health Commission Public Hearings in Durham, where key themes were discussed in front of a public audience, and a meeting of the Mental Health Action Team, where the group refined the ‘asks’ of the report.

Due to my interest in mental health, and experience in this area of research, I wrote the ‘Context’ section of the report, which aimed to set the tone, and provide the audience with relevant information about mental health in the region, and further afield. I was also able to provide relevant literature for, and make comments on the themed sections of the report, which were written by the editor.

Coming from a qualitative research background, it was interesting to learn about the methodologies employed by the Citizens for this piece of work. Community organising is a process where people who live locally come together into an organisation that acts in their shared self-interests. This method was used in order to best capture the voices of those who may not engage with traditional methods of research. This was one of the most fascinating insights I gained from the process, and I believe this method of collective power from the community, could be utilised in directing future public health research, and that groups such as these may well be a starting point for meaningful patient and public involvement work. 

The Citizens had a small pot of money to support our involvement, and seven working days were costed for me to undertake the work. The biggest challenge I faced was the tight timescale. I was working full-time across other projects, and was in the process of writing my MSc dissertation, so the work had to fit around these existing commitments, which meant working outside of normal work hours.

The final report was launched in November 2018, at an event attended by over 500 people at Newcastle’s Civic Centre. Eileen and I were delighted to attend and speak at the event, and it was fantastic to see so many individuals interested in finding out about the work. Although the timescale was tight, I thoroughly enjoyed the opportunity to be involved in this important and innovative piece of work. I had a great working relationship with Simon and Joe, and was well supported by Eileen and Lesley. 

I am passionate about mental health research, and I am proud to have played a part in the production of a report, which aims to improve the lives of those in my home region.

Find out more about the work on the Citizens UK website.