BBCThey are the black Pete from many nutritionists – mass-produced yet delicious foods such as chicken nuggets, packaged snacks, soft drinks, ice cream or even sliced brown bread.
So-called ultra-processed foods (UPF) account for 56% of calories consumed in the UKand that figure is higher for children and people living in poorer areas.
UPFs are defined by the number of industrial processes they have undergone and the number of ingredients – often unpronounceable – on their packaging. Most are high in fat, sugar or salt; many are considered fast food.
What they have in common is their synthetic appearance and taste, which has made them a target for clean living advocates.
There’s growing evidence that these foods are bad for us. But experts can’t agree on exactly how they affect us or why, and it’s not clear whether science will give us an answer any time soon.
While recent research shows that there are many widespread health problems, including cancer, heart disease, obesity and depression, linked There is no evidence yet that UPFs causes by them.
For example, a recent meeting of the American Society for Nutrition in Chicago was presented with an observational study of more than 500,000 people in the U.S. It found that those who ate the most UPFs had about a 10 percent greater chance of dying, even after taking into account their body mass index and the overall quality of their diet.
In recent years, many other observational studies have shown a similar association, but that is not the same as proving that How food processing causes health problems, or what aspect of those processes might be the cause.
How can we find out the truth about ultra-processed foods?
According to Dr Nerys Astbury, a senior researcher in nutrition and obesity at the University of Oxford, the type of research needed to definitively prove that UPFs cause health problems would be extremely complex.
It would have to compare a large number of people on two diets – one high in UPFs and one low in UPFs, but exactly equal in calorie and macronutrient content. That would be devilishly difficult to actually do.
Participants would have to be kept under lock and key so that their food intake could be strictly controlled. The study would also have to enroll people with similar diets as a starting point. It would be extremely challenging logistically.
To counter the possibility that people who eat fewer UPFs might actually have healthier lifestyles, such as exercising more or sleeping more, the participants in the groups would have to have very similar habits.
“It would be expensive research, but you could see changes in diet relatively quickly,” says Dr. Astbury.
Funding for this type of research can also be hard to come by. There can be accusations of conflict of interest, as researchers who are motivated to conduct these types of trials may already have an idea of what they want the conclusions to be before they begin.
These trials couldn’t last long anyway – too many participants would probably drop out. It would be impractical to tell hundreds of people to stick to a strict diet for more than a few weeks.
And what could these hypothetical experiments actually prove?
Getty ImagesDuane Mellor, head of nutrition and evidence-based medicine at Aston University, says nutrition scientists can’t prove specific foods are good or bad, or what effect they will have on an individual. They can only show potential benefits or risks.
“The data doesn’t show more or less,” he says. Claims to the contrary are “bad science,” he says.
Another option is to look at the effect of common food additives in UPFs on a laboratory model of the human gut. Scientists are busy doing that.
There is an even bigger problem, however: the confusion about what is actually considered UPF.
They usually contain more than five ingredients, only a few of which you’ll find in an average kitchen cupboard.
Instead, they are usually made from cheap ingredients such as modified starches, sugars, oils, fats and protein isolates. To make them more appealing to the taste buds and eyes, flavour enhancers, colourings, emulsifiers, sweeteners and glazing agents are added.
They range from the obvious (sugary cereals, sodas, slices of American cheese) to perhaps the most unexpected (supermarket hummus, low-fat yogurt, some granolas).
And this begs the question: How useful is a label that puts chocolate bars in the same class as tofu? Can some UPFs affect us differently than others?
To find out more, BBC News spoke to the Brazilian professor who coined the term “ultra-processed foods” in 2010.
Prof Carlos Monteiro also developed the Nova classification system, which ranges from ‘whole foods’ (such as legumes and vegetables) at one end of the spectrum, through ‘processed culinary ingredients’ (such as butter) and then ‘processed foods’ (things like tinned tuna and salted nuts) all the way up to UPFs.
The system was developed after obesity in Brazil continued to rise while sugar consumption fell, and Prof Monteiro wondered why. He believes that our health is affected not only by the nutritional value of the food we eat, but also by the industrial processes used to make and preserve it.
He says he didn’t expect the current surge in attention to UPFs, but he argues that “it’s contributing to a paradigm shift in nutritional science.”
However, many nutritionists say the fear of UPFs is overblown.
Gunter Kuhnle, professor of nutrition and food science at the University of Reading, says the concept is “vague” and the message it sends is “negative”, leaving people feeling confused and fearful about food.
It is true that there is currently no concrete evidence that the way food is processed is harmful to our health.
We process food every day: cutting, cooking and freezing are all processes that are not harmful.
And when food is processed on a large scale by manufacturers, it ensures that the food is safe, has a longer shelf life and there is less waste.
Take frozen fish sticks for example. They use up leftover fish, feed kids healthy and save parents time – but they still count as UPFs.
Getty ImagesAnd what about meat substitutes like Quorn? Granted, they don’t resemble the original ingredient they’re made from (and therefore fall under Nova’s definition of UPFs), but they’re considered healthy and nutritious.
“If you make a cake or a brownie at home and compare it to a cake or brownie that is already in a packet and has flavour enhancers in it, do I think there is a difference between the two foods? No, I don’t think so,” Dr Astbury tells me.
The Food Standards Agency, the UK’s food safety body, has acknowledged reports that people who eat high levels of UPFs are at greater risk of heart disease and cancer. However, the agency says it will not take action on UPFs until there is evidence that they cause specific harm.
Last year, the government’s Scientific Advisory Committee on Nutrition (SACN) reviewed the same reports and concluded that there were “uncertainties about the quality of the available evidence”. It also had some concerns about the practical application of the Nova system in the UK.
Prof. Monteiro, for his part, is most concerned about processes involving intense heat, such as the production of breakfast cereal flakes and puffs, which he claims “break down the natural food matrix”.
He points to a small study that shows this leads to a loss of nutrients and makes us feel less full, making us more likely to make up for the deficit with extra calories.
It’s also hard to ignore the lingering sense of self-righteousness and — whisper it — snobbery surrounding UPFs, which can make people feel guilty about eating them.
Dr Adrian Brown, a dietitian and senior research fellow at University College London, says demonising one food doesn’t help, especially when what and how we eat is such a complex issue. “We need to be aware of the moralisation of food,” he says.
Living a UPF-free life can be expensive, and it takes time, effort, and planning to prepare meals yourself.
a recent report from the Food Foundation found that healthier foods cost twice as much as less healthy foods per calorie, and that the poorest 20% of the UK population would have to spend half their disposable income on food to meet government requirements recommendations for a healthy dietIt would cost the richest people only 11% of their income.
I asked Prof Monteiro if it is even possible to live without UPFs.
“The question here should be: is it feasible to stop the growing consumption of UPFs?” he says. “My answer is: it is not easy, but it is possible.”
Many experts say the current traffic light system on food labels (which indicates high, medium and low sugar, fat and salt contents) is simple and useful enough as a guide when shopping.
For the uncertain shopper, there are now smartphone apps available, such as the Yuka app. With this you scan a barcode and get insight into how healthy the product is.
And of course, there’s the advice you already know: eat more fruits, vegetables, whole grains, and beans, and limit fatty and sugary snacks. Sticking to that is still a good idea, whether or not scientists prove UPFs are harmful.
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