It's hard to miss the alarming headlines linking ultra-processed foods (UPFs) with multiple health risks. But are these foods really something to worry about? We asked Dietitian Laura Tilt to explain the research so you can better understand what it means for your health.
Almost all the food and drink you eat has been processed in some way, and humans have been eating processed food for thousands of years. This isn’t a bad thing; food processing makes food safer (think raw vs pasteurised milk), increases shelf life and reduces food waste. It means we can prepare meals in less time with less effort and it increases choice and dietary diversity, which is good news for your gut microbiome.
But recent concerns around processed food relate to the amount of highly processed or ultra-processed food (UPF) in our diets. A study from 2019 found that almost 60% of our daily calories come from ultra-processed foods, and in some groups of children, it's as much as 80%. It makes sense to explore how UPFs affect our health when they are such a big part of our diets.
What makes a food ultra-processed?
There’s no universally agreed definition of an ultra processed food. The most widely used is something called the NOVA classification. This was devised by Brazilian nutrition and health researcher Professor Carlos Monteiro. He argued that the extent a food is processed was more influential to health than its nutritional value. The NOVA classification divides foods into four groups according to the level of processing:
NOVA group 1: unprocessed or minimally processed foods. This includes fruit and vegetables, meat, eggs, milk, nuts, seeds, dried pasta and couscous.
NOVA group 2: processed culinary ingredients. These are obtained from group 1 foods or from nature, that are used in preparing meals. Examples include butter and oils, honey and sugar, salt and vinegar.
NOVA group 3: processed foods. These are made by adding salt, sugar or other substances found in group 2 to group 1 foods, using preservation methods like canning and bottling, or fermentation. Examples include freshly baked bread, many cheeses, and canned vegetables.
NOVA group 4: ultra-processed foods. These are products formed from ingredients that have gone through multiple industrial processes like extracting, extruding and pressuring. Additives and emulsifiers are added to improve taste or appearance. Examples include fizzy drinks, margarine, breakfast cereals, protein bars, filled pasta, sausages, fish fingers, wholemeal bread and instant noodles.
It’s important to remember that the NOVA classification ignores the nutritional content of food. This means the UPF category contains a few surprises. Alongside hotdogs, sweets and doughnuts, wholemeal bread, jarred pasta sauce and plant milks get the UPF label too.
So what’s the concern with UPFs?
Since the NOVA classification was published, over 1,000 studies have linked eating UPFs with an increased risk of health problems including certain types of cancer, obesity and heart disease.
More recent headlines relate to a study published in the British Medical Journal in February 2024. This study pooled data from multiple existing studies looking at the relationship between UPF and health outcomes, and included data from nearly 10 million people. The results found convincing evidence that higher intakes of UPF (as classified using the NOVA system) were linked a higher risk of:
- heart disease, heart attacks and stroke
- type 2 diabetes
- common mental health problems like anxiety
Woah! So UPFs really are bad for our health?
Well it’s not as clear-cut as it seems. Almost all the research around UPF and health comes from observational studies. These can help identify relationships – for example, finding a link between UPFs and health conditions – but they can’t prove that UPFs are the direct cause of that condition. Other factors might be at play, and we need to understand what’s driving the relationship.
Only one randomised controlled trial (which can show cause and effect) has directly studied the impact of a diet high in UPFs. In the study, 20 healthy volunteers ate either an UPF-rich diet with 80% of calories from NOVA group 4, or a minimally processed diet (no UPF) for two weeks, whilst living at a medical centre.
Each diet was matched for calories, sugars, fibre, fat, salt, and carbohydrates, so the only difference was the level of processing. So for example, an ultra-processed (UPF) breakfast consisted of Cheerios, milk, and a blueberry muffin with margarine, while a minimally processed (MP) breakfast consisted of oatmeal with milk, fruit, and almonds.
Volunteers were not told what was being measured; just that they could eat as much or as little as they liked. During the ultra-processed diet, volunteers ate about 500 calories more per day and gained about a kilogram in weight. What the study wasn’t able to answer is why people ate more of the UPF diet, as participants rated the diets equally in terms of taste and appetite ratings.
So what’s the issue with UPF?
This is the million-pound question and the missing piece of the UPF puzzle. Many (though not all) UPFs are high in fat, sugar, and salt, and low in fibre. These are what scientists call "hyperpalatable" foods - especially tasty and hard to stop eating. But scientists are also curious about other factors at play. For example:
- Increased eating Rate: UPFs are often soft and require less chewing, which might lead to a faster eating rate and eating more calories as a result.
- Food Additives: Many UPFs contain additives like preservatives, emulsifiers and sweeteners which play a role in food safety, texture or flavour. While some have neutral effects, there’s evidence that some may affect the gut and alter the microbiome in ways that drive inflammation.
- Changes to the Food Matrix: Processing changes the structure of foods, which might impact how our bodies digest and absorb nutrients, and the impact this has on appetite.
These hypotheses need to be tested in experimental studies before we understand how to address UPFs. So if additives are a problem, they can be restricted. If it’s about texture, could this be improved by adding a crunchy salad to a UPF meal? If it’s simply that many UPFs are hyperpalatable and not very filling, then we will be able to sub-categorise UPF by the nutrients they contain.
Surely we should just ban or tax UPFs?
This isn't an all-or-nothing situation, and not all UPFs are the same. Some, like wholemeal bread and wholegrain cereals, contribute positively to a healthy diet. Recent studies on specific categories within NOVA have shown that wholegrains don't seem to pose the health risks associated with other UPFs. Is wholegrain pasta with a jarred veggie sauce and tuna an unhealthy meal because it contains a UPF? Absolutely not.
Taxing or banning UPFs would unfairly penalise people who rely on them for specialist diets or medical needs. Gluten free products, infant formula and plant milks are all categorised as UPFs. UPF’s can help you put together a meal more quickly, with less effort.
So what should we do?
It's easy to get swept up in the buzz about UPFs, but the truth is, by following the UK’s existing nutrition guidelines, you’ll inherently be limiting UPFs. Is eating some UPFs as part of a healthy, balanced diet a problem? It's unlikely, because, as with everything, the dose matters.
It's also important to remember that demonising food isn't helpful. Labels like "bad" or "evil" only increase anxiety and guilt around food choices. More research is being done to understand how UPFs affect health, which will make things clearer. Until then, we can stick to the choices we know are backed by good research and remember that food is more than just nutrition. Enjoying meals, having choice and maintaining a positive relationship with food is also important for your well-being.
Want to read more from our Fact v Fiction series with Laura Tilt?
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