they are the bête noire from many nutritionists – mass produced but worse foods such as chicken nuggets, packaged snacks, fizzy drinks, ice cream or even sliced brown bread.
So-called ultra-processed foods (UPF). they account for 56% of calories consumed across the UKand that figure is higher for children and people who live in poorer areas.
UPFs are defined by how many industrial processes they have undergone and the number of ingredients – often unpronounceable – on their packaging. Most are high in fat, sugar or salt; pretty much what you would call fast food.
What they have in common is their synthetic look and taste, which has made them a target for some clean-living advocates.
There is a growing body of evidence that these foods are not good for us. But experts can’t agree on exactly how they affect us or why, and it’s not clear that science is going to give us an answer anytime soon.
Although recent research shows many pervasive health problems, including cancers, heart disease, obesity and depression connected to UPFs, there is no proof, yet, that they are caused it at them.
For example, an observational study of more than 500,000 people in the US was presented at a recent meeting of the American Association for Nutrition in Chicago. It found that those who ate the most UPFs were about 10% more likely to die, even accounting for their body mass index and the overall quality of their diet.
In recent years, several other observational studies have shown a similar link – but that doesn’t prove it how processed food causes health problems, or describes the aspects of those processes that may be at fault.
So how can we find the truth about ultra-processed food?
The type of study needed to definitively prove that UPFs cause health problems would be extremely complex, says Dr Nerys Astbury, a senior researcher in diet and obesity at the University of Oxford.
It would require comparing a large number of people who were on two diets – one high in UPFs and one low in UPFs, but precisely matched for calorie and macronutrient content. This would be very difficult to do in reality.
The participants would have to be locked up so that their food intake could be strictly managed. The study would also need to enroll people with similar diets as a starting point. It would be very logistically challenging.
And to counter the possibility that people who eat fewer UPFs might have healthier lifestyles, for example by exercising more or getting more sleep, participants in the groups would have to have very similar habits to have
“It would be expensive research, but you could see changes from the diets relatively quickly,” says Dr Astbury.
Funding for this type of research may also be difficult to come by. There may be accusations of conflicts of interest, since researchers motivated to run trials of this type may have an idea of what they want the conclusions to be before they begin.
These trials couldn’t last very long, anyway – too many participants would probably drop out. It would not be practical to tell hundreds of people to stick to a strict diet for more than a few weeks.
And what might these hypothetical tests actually prove, anyway?
Duane Mellor, head of nutrition and evidence-based medicine at Aston University, says nutrition scientists cannot prove that specific foods are good or bad or what effect they 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 would be to look at the effect of common food additives present in UPFs on a laboratory model of the human gut – something scientists are busy doing.
There is a wider issue though – the amount of confusion surrounding what actually counts as UPFs.
They generally contain more than five ingredients, few of which you would find in a typical kitchen cupboard.
Instead, they are usually made from cheap ingredients such as modified starches, sugars, oils, fats and protein isolates. Then, to make them more appealing to the taste buds and the eyes, flavor enhancers, colors, emulsifiers, sweeteners and glazing agents are added.
They range from the most obvious (sugary breakfast cereals, fizzy drinks, American cheese slices) to the more unexpected (supermarket yogurt, low-fat, some mueslis).
And this raises the questions: how helpful is a label that puts chocolate bars in the same league as tofu? Could some UPFs affect us differently than others?
To find out more, BBC News spoke to the Brazilian professor who came up with the term “ultra-processed food” in 2010.
Professor Carlos Monteiro also developed the Nova classification system, which includes “whole foods” (such as legumes and vegetables) at one end of the spectrum, through “processed cooking ingredients” (such as butter) and “processed foods” (things such as canned tuna and salted nuts) all the way to UPFs.
The system was developed after obesity in Brazil continued to rise as sugar consumption fell, and Professor Monteiro wondered why. He believes that our health is affected not only by the nutritional content of the food we eat, but also by the industrial processes used to make and preserve it.
He says he didn’t expect the huge attention UPFs are getting right now but claims “it is contributing to a paradigm shift in nutritional science”.
However, many nutritionists say that UPFs are afraid of overheating.
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 afraid of food.
It is true that there is currently no concrete evidence that the way food is processed harms our health.
Processing is something we do every day – chopping, boiling and freezing are processes, and those things are not harmful.
And when food manufacturers process food at scale, it helps ensure food is safe, lasts longer and reduces waste.
Take frozen fish fingers for example. They use leftover bits of fish, provide some healthy food for the kids and save parents time – but still count as UPFs.
And what about meat replacement products such as Quorn? Granted, they don’t look like the original ingredient they’re made from (and therefore fall under Nova’s definition of UPFs), but they are seen as healthy and nutritious.
“If you make a cake or a brownie at home and compare it to the one that already comes in a packet with flavor enhancers, do I think there is any difference between those two foods? I can’t,” Dr Astbury tells me.
The body responsible for food safety in England, the Food Standards Agency, acknowledges reports that people who eat a lot of UPFs have an increased risk of heart disease and cancer, but says it will not take any action on UPFs until there is evidence there. causing particular harm.
Last year, the government’s Scientific Advisory Committee on Nutrition (SACN) looked at the same reports and concluded that there were “uncertainties about the quality of the available evidence”. He also had some concerns about the practical application of the Nova system in the UK.
For his part, Professor Monteiro is more concerned about processes involving intense heat, such as the manufacture of breakfast cereal flakes and puffs, which he claims “degrades the natural food matrix”.
He points to a small study that suggests this results in a loss of nutrients and therefore leaves us feeling less full, meaning we are more tempted to make up the deficit with extra calories.
It’s also hard to ignore the growing righteousness and – whisper it – snobbery around UPFs, which makes people feel guilty for eating them.
Dr. Adrian Brown, a specialist nutritionist and senior research fellow at University College London, says that demonizing one type of food is not helpful, especially when what and how we eat is such a complex issue. “We have to be mindful of the morality of food,” he says.
UPF-free living can be expensive—and cooking meals from scratch takes time, effort, and planning.
A a recent Food Foundation report found that healthier foods were twice as expensive 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 the government’s income . healthy diet recommendations. It would cost the richest people only 11% of theirs.
I asked Professor Monteiro if it is even possible to live without UPFs.
“The question here should be: is it possible to stop the increasing consumption of UPFs?” he says. “My answer is: it is not easy, but it is possible.”
Many experts say that the current system of traffic lights on food labels (which indicate high, medium and low levels of sugar, fat and salt) is simple and helpful enough to guide you when shopping.
Smartphone apps are now available for the indecisive shopper, such as the Yuka app, which allows you to scan barcodes and get a breakdown of how healthy the product is.
And of course there’s the advice you already know – eat more fruit, vegetables, whole grains and beans, and cut back on fatty and sugary snacks. It’s still a good idea to stick to that, whether or not scientists prove that UPFs are harmful.
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