Ultra-processed foods (UPFs) might taste good and provide an easy hunger fix, but their long-term health consequences are starting to scare nutrition experts.
These foods are often high in added sugars, salt and saturated fats, while being low in protein, fibre and essential micronutrients – making them energy dense and nutritionally poor. They also frequently contain a cocktail of additives to improve taste, texture, colour and shelf life.
We’re talking foods like fizzy drinks, packaged biscuits and cakes, breakfast cereals, mass-produced bread, ready meals, flavoured yoghurts, processed meats and some fast food.
Now, eating some UPFs as part of an otherwise healthy diet is okay. Life wouldn’t be as good without bacon, biscuits and burgers after all.
There’s also no denying that processed foods are useful for those short on time and cash – two things most of us never seem to have enough of. But problems arise when the occasional treat turns into an everyday staple.
Regularly eating large amounts of UPFs has been linked to a plethora of diseases. And, rather concerningly, the largest world review to date recently found that UPFs are linked to harm in every major organ system in the body.
Which makes it pretty alarming that, in both the UK and the US, more than half of the average diet is made up of UPFs.
While most of us know that UPFs aren’t great for our health, spotting them isn’t always easy. Plenty of everyday foods that seem harmless are hiding overly-processed ingredients that may be bad for us.
So, to help you make more informed choices, here’s our guide to the archvillains – the ingredients you should really try to limit or avoid if you’re putting your health first.
1. Artificial colourings
Artificial colourings are lab-made chemical dyes added to foods to enhance or replace colour lost during processing.
In the EU and UK, these appear as E-numbers on ingredients lists (codes used for additives that have been tested and approved for use in food), or as FD&C colours in the US (Food, Drug & Cosmetic dyes approved by the FDA).
Three that raise the biggest red flags are Tartrazine (E102 / FD&C Yellow 5), Sunset Yellow (E110 / FD&C Yellow 6) and Allura Red (E129 / FD&C Red 40). These dyes are used in sweets, fizzy drinks, desserts and breakfast cereals.
They also sneak into less obvious foods like sauces, cheeses and vegan meat alternatives, where they’re used to give a more meat-like colour.
These dyes are best known for their links to behavioural effects in children. A large amount of research has connected them to hyperactivity, difficulty concentrating and mood changes in some kids, and they may worsen ADHD symptoms.
In the UK and EU, foods containing these colours must carry a warning saying they “may have an adverse effect on activity and attention in children.” As a result, many UK brands have quietly removed them, and the Food Standards Agency (FSA) actively encourages manufacturers to cut back.
In the US, these same dyes are still widely used and don’t need warning labels, so you might want to keep an eye out for them. Growing concern has led to restrictions in schools, and increasing pressure to tighten the rules.
2. Nitrates and nitrites
These preservatives are commonly added to processed meats such as bacon, sausages, ham and deli meats to extend their shelf life and give meat its familiar pink colour and tasty cured flavour.
Nitrates themselves aren’t harmful, but bacteria used in food processing and in the mouth can convert them into nitrites. We’d particularly advise looking out for sodium nitrite (E250), sodium nitrate (E251), potassium nitrite (E249) and potassium nitrate (E252).
These are more reactive and, in the acidic environment of the stomach, can form nitrosamines – nasty compounds linked to an increased risk of bowel cancer.
For this reason, in 2015, the World Health Organization (WHO)’s International Agency for Research on Cancer (IARC) declared processed meat to be carcinogenic, and UK scientists are now urging the government to put cancer warnings on bacon and ham.
Adding to the body of evidence, in January 2026, two large French studies linked higher intakes of nitrates, nitrites and other common preservatives to both cancer and type 2 diabetes.
These findings came from the NutriNet-Santé cohort, an ongoing French population study that tracks the diets and health of more than 100,000 adults.
“This is the only study in the world able to accurately quantify exposure to a wide range of food additives and link it to long-term health outcomes in real-world diets,” says Dr Mathilde Touvier, Research Professor at the French National Institute for Health and Medical Research (Inserm) and principal investigator of the NutriNet-Santé cohort.
In the cancer study, higher intake of sodium nitrite was linked to an increased risk of prostate cancer. By age 60, the absolute risk – meaning the actual proportion of people who develop the disease – rose from around 3.4 per cent in lower consumers to 4.2 per cent in higher consumers.
A similar pattern was seen for breast cancer, where higher intake of potassium nitrate was associated with an increase in absolute risk from about 4.8 per cent to 5.9 per cent by age 60.
Although these increases are modest for individuals, even small rises in absolute risk could translate into a significant number of additional cases across the population.
In the diabetes study, people with the highest intake of food preservatives, including sodium nitrite, had a 47 per cent higher risk of developing type 2 diabetes compared with those with the lowest intake.
The good news is that these studies don’t suggest cutting out foods like ham, bacon or sausages entirely. Instead, they link the gradual increase in risk with a higher and more frequent consumption of nitrite- and nitrate-containing foods.
The lowest intake groups still consumed these foods, just less often and in smaller amounts. So it’s more than okay to indulge in the occasional bacon sandwich.
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3. Emulsifiers
Emulsifiers are one of the most common additives in processed foods. They help ingredients like oil and water mix (or emulsify) and stay stable, giving foods both a smoother texture and longer shelf life.
Out of the long list of emulsifiers used today, carboxymethylcellulose and polysorbate-80 have consistently shown up as the bad guys – you’ll find these in mass-produced bread and baked goods, ready meals, frozen pizzas, burgers and chicken nuggets, sauces, spreads and sweets.
The main worry is how they affect the gut microbiome – the trillions of microbes living in and interacting with your digestive system to help keep you healthy. Several studies suggest that carboxymethylcellulose and polysorbate-80 can interfere with this delicate environment.
In one study, both emulsifiers caused lasting changes to gut microbes and altered the microbiome in a way that promotes gut inflammation.
Chronic inflammation like this is thought to increase the risk of conditions such as inflammatory bowel disease (IBD) and metabolic syndrome, which in turn raises the risk of type 2 diabetes and heart disease.
Another study found that these microbiome changes were linked to significant weight gain and suggests that the widespread use of these emulsifiers could be contributing to rising levels of obesity and chronic inflammatory conditions such as IBD.
But avoiding these ingredients might not be as easy as you think. “Some foods have a ‘health halo’, which can mask the fact they’re ultra-processed,” explains Touvier.
“Multi-cereal breads, for example, may look nutritious, but can still contain several emulsifiers and additives, so it’s worth checking the ingredients list.”
“Low-fat yoghurts are another example. Fat is often removed and replaced with emulsifiers to recreate a creamy texture.”
For now, these emulsifiers are still considered safe by food authorities and experts say there’s no need to avoid them entirely, especially as they appear in many foods that also provide important nutrients.
4. Interesterified palm oil
Interesterified palm oil is a common ingredient in UPFs such as margarines and spreads, biscuits, cakes, pastries and chocolate, as well as some dairy alternatives.
Through the interesterification process, fat molecules are chemically rearranged, so the fat behaves differently. It makes spreads easier to spread, for example, as well as flakier baked goods, and products that last longer on the shelves.
Interesterified fats were introduced to replace trans fats, which are known to be extremely bad for heart health.
While they’re widely seen as a safer alternative, we still don’t fully understand their long-term effects on health.
The main concern comes from the interesterification process, which essentially allows saturated fats to be more efficiently absorbed and metabolised.
Studies using commercial palm oil blends show that these can lead to higher spikes in blood fats after meals compared with noninteresterified fats. This puts extra strain on the heart and blood vessels and is linked to a higher risk of heart disease over time.
One of the biggest problems is that these fats are hard to spot. There’s no requirement for food labels to say when a fat has been interesterified, so it may simply appear as ‘palm oil’ on the ingredients list.
That means most people have no idea how much they’re eating, and researchers don’t yet know how much the average person consumes either.
“For now, the safest bet is to limit how often you eat highly processed foods that rely heavily on these engineered palm fats, especially if they’re a regular part of your diet,” says Touvier.
5. High-fructose corn syrup
High-fructose corn syrup (HFCS) is an artificial sugar made from corn starch that’s widely used to sweeten processed foods and drinks, especially in the US. It turns up in everything from fizzy drinks and cereals to yoghurts, sweets and even savoury foods like bread, soups and ketchup.
Most HFCS is around 55 per cent fructose. Unlike glucose, which your body can use straight away, fructose has to be processed by the liver, where excess amounts are more likely to be turned into fat. This is why HFCS is thought to be particularly harmful when eaten in large amounts.
Although fructose is found naturally in fruit, it comes in much smaller quantities and is packaged with fibre, which slows absorption and reduces harm.
A large body of research links high HFCS intake to several serious health problems, such as fatty liver disease, insulin resistance, type 2 diabetes, obesity and heart disease.
HFCS can also upset your gut microbiome. Studies suggest it reduces “good” gut bacteria, increases inflammation and weakens the gut lining, which may contribute to weight gain, poor blood sugar control and digestive conditions such as irritable bowel syndrome (IBS).
As a guideline, the WHO recommends keeping free sugars – all sugars added to foods, plus those found naturally in honey, syrups and fruit juices – below 10 per cent of your energy intake.
On ingredient lists, HFCS is usually listed as high-fructose corn syrup in the US, while in the UK and EU it often appears as glucose-fructose syrup or fructose-glucose syrup.
The cocktail effect
Another major focus of Touvier’s research is what happens when food additives are consumed together, rather than on their own.
When additives are approved for use in food, regulators such as the European Food Safety Authority (EFSA) and the Food and Drug Administration (FDA) assess them individually.
But over the course of a day, we can easily consume several additives at the same time, especially since many UPFs contain combinations of them. Yet there’s very little research into the health effects of consuming additives this way.
This means we still don’t really know what these mixtures of preservatives could be doing to our bodies.
In 2025, Touvier and her team published a study that used a data-driven approach to identify the main food-additive mixtures people consume in everyday diets. Out of the five common mixtures they identified, two stood out.
One was dominated by emulsifiers and texture-modifying additives found in many processed foods, and the other by additives typically seen in sugary or artificially sweetened drinks.
“We found that people with higher exposure to these two additive mixtures were more likely to develop type 2 diabetes than those with lower exposure, after accounting for diet quality and lifestyle factors,” says Touvier.
“There are also experimental studies that have tested additive mixtures – based on real-world consumption patterns – on human cells, including gut, liver and brain cells.
"These studies found effects from mixtures that couldn’t be explained by individual additives alone, suggesting a cocktail effect.”
Think before you chew
This list includes just a small handful of ingredients in UPFs that may be bad for our health – there are unfortunately many more. But with UPFs now so embedded in modern diets, and temptation lurking on every supermarket shelf, avoiding them completely is an unrealistic goal for most of us.
What matters is knowing how to spot them so you can make informed decisions about when you choose to eat UPFs, understanding where the risks lie and limiting their impact.
To make healthier choices, Touvier suggests starting with the basics. “Salt, sugar, fibre and the type of fat are most important,” she says, “so checking the nutrition label can give you a quick sense of whether a food is a good choice.”
Her second tip is not to get too bogged down in individual ingredients. “As a general rule, if a product has a long ingredient list filled with things you wouldn’t use in your own kitchen, it’s probably ultra-processed.”
Overall, the healthiest approach is to choose fresh or minimally processed foods where you can, without aiming for perfection. There’s nothing wrong with the occasional sweet treat or a cheeky bacon sandwich, but go for the less-processed option whenever you can.
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