Why the truth about ultra-processed foods will never be known
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Author, Philippa Roxby Role, Health Reporter
3 hours ago
Mass-produced yet tempting foods like chicken nuggets, packaged snacks, soda, ice cream, and even sliced brown bread are anathema to many nutritionists.
UPF is defined by how much industrial processing a food has undergone and the number of (often unpronounceable) ingredients listed on the packaging. Most foods are high in fat, sugar and salt and are considered fast food.
What they all have in common is an artificial look and taste, which makes them a target for clean living advocates.
There’s growing evidence that these foods are bad for your health, but experts still don’t agree on why or how these foods affect your health, and it’s unclear whether science will provide answers anytime soon.
Recent studies have shown that many prevalent health problems, including cancer, heart disease, obesity, and depression, are associated with UPF, but there is still no evidence that the problems are caused by UPF.
For example, an observational study of more than 500,000 people in the US was presented at a recent meeting of the American Academy of Nutrition in Chicago and found that those who consumed the most UPF were about 10% more likely to die, even after accounting for body mass index and overall quality of their diet.
A number of other observational studies in recent years have shown similar associations, but this does not prove that the way food is processed causes the health problems or identify which aspect of the processing is to blame.
So how do we get to the truth about ultra-processed foods?
The kind of research needed to conclusively prove that UPF causes health problems would be extremely complex, suggests Dr Nerys Astbury, a senior research fellow in diet and obesity at the University of Oxford.
You’d need to compare a lot of people eating two diets, one with a high UPF and one with a low UPF (but with perfectly matched calorie and macronutrient content), which is very difficult to do in practice.
Participants would need to keep their food intake in a locked location to ensure strict control, and the study would also need to enroll people with similar dietary habits at the start, which would be logistically very challenging.
Also, to counter the possibility that people who consume less UPF may be living a healthier lifestyle by exercising more or sleeping more, participants in the groups would need to have very similar habits.
“Studies are expensive, but dietary changes are likely to be seen relatively quickly,” Dr Astbury said.
Obtaining funding for this type of study may also be difficult, and there may be suspicions of conflict of interest because researchers who are motivated to conduct this type of trial may have an idea of what conclusions they want to reach before they even begin the trial.
In any case, such a trial would not last very long: Too many participants would probably drop out, and asking hundreds of people to continue a strict diet for more than a few weeks would be unrealistic.
But what exactly could these hypothetical tests prove?
Image credit: Getty Images
Image caption, UPF is a common sight on supermarket shelves, but some are surprising
Duane Mellor, a reader in nutrition and evidence-based medicine at Aston University, says nutritionists can’t prove whether a particular food is good or bad, or how it affects an individual — they can only point to potential benefits or risks.
“The data shows no more, no less,” he said, and claims to the contrary “lack scientific basis,” he said.
Another option would be to examine the effects of common food additives, such as those found in UPF, on experimental models of the human gut, something scientists are busy working on.
But there’s a bigger problem: the level of confusion about what actually counts as UPF.
Typically, they contain five or more ingredients, most of which aren’t found in the average kitchen cupboard.
Instead, they are typically made from cheaper ingredients such as modified starches, sugars, oils, fats and protein isolates, and then flavor enhancers, colors, emulsifiers, sweeteners and glazing agents are added to make them more appealing to the palate and the visual sense.
They range from the obvious (sugary breakfast cereal, soda, slices of American cheese) to the perhaps more surprising (supermarket hummus, low-fat yogurt, muesli).
And it begs the question: How useful is a label that puts a chocolate bar on the same level as tofu? Might 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.
Professor 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 cooking ingredients” (such as butter) and “processed foods” (such as canned tuna and salted nuts) to the UPF.
The system was developed after sugar consumption in Brazil fell while obesity continued to rise, leading Professor Monteiro to wonder why. He believes our health is influenced not only by the nutritional content of the food we eat, but also by the industrial processes used to make and preserve it.
He said he did not expect UPF to receive the attention it has now, but argues that it is “contributing to a paradigm shift in nutrition science.”
But many nutritionists say fear of UPF is overblown.
Gunter Kuhnle, professor of nutrition and food science at the University of Reading, said the concept was “vague” and the message it sent was “negative”, leaving people confused and scared of food.
Indeed, at present there is no concrete evidence that the way food is processed is harmful to our health.
Processing is something we do every day: cutting, boiling, freezing, etc. are all processes and they are not harmful.
Also, when food is processed on a large scale by manufacturers, it ensures food safety, can be stored for longer, and waste is reduced.
Take frozen fish fingers for example: they use leftover fish scraps, provide a healthy meal for kids, save parents time, and still count as UPF.
Image credit: Getty Images
Image caption, Some experts say demonizing certain foods isn’t helpful
So what about meat alternatives such as Quorn? Sure, they bear no resemblance to the original ingredients used in their production (and therefore fall under Nova’s UPF definition), but they are still considered healthy and nutritious.
“If you compare a cake or brownie you make at home with a pre-packaged one that already has flavour enhancing additives in it, do you think there’s a difference between the two foods? No, I don’t think there is a difference,” Dr Astbury told me.
The Food Standards Agency, the body responsible for food safety in England, acknowledges reports that people who eat high amounts of UPF are at increased risk of heart disease and cancer, but says it will not take any action on UPF until there is evidence it causes specific harm.
Last year the government’s Scientific Advisory Committee on Nutrition (SACN) reviewed the same report and concluded there was “uncertainty about the quality of the available evidence”. It also raised concerns about the rollout of the Nova system in the UK.
However, Professor Monteiro’s main concern is with processes that involve high heat, such as making breakfast cereal flakes or puffs, which he argues “degrades the natural food matrix”.
He points to small studies suggesting this leads to a loss of nutrients, which makes people feel less full and more tempted to make up for the loss with extra calories.
It’s also hard to ignore the creeping sense of smugness surrounding UPF and, whisper it, the condescending attitude that makes you feel guilty about eating it.
Dr Adrian Brown, expert nutritionist and senior research fellow at University College London, says demonising certain foods is unhelpful when the issue of what and how we eat is so complex. “We have to be careful about moralising food,” Dr Brown says.
Living without UPF can be expensive, and cooking meals from scratch takes time, effort, and planning.
A recent Food Foundation report found that healthier foods are twice as expensive per calorie as less healthy foods and that the poorest 20% of the UK population would need to spend half their disposable income on food to meet the government’s healthy eating recommendations – compared with just 11% for the richest.
I asked Professor Monteiro whether it was possible to live without UPF.
“The question is: can we stop the increase in UPF consumption?” he says. “My answer is: It’s not easy, but it is possible.”
Many experts say the current traffic light system on food labels – indicating high, medium or low levels of sugar, fat and salt – is simple and serves as a good guide for shoppers.
For anxious shoppers, there are now smartphone apps available, such as the Yuka app, which allows you to scan a barcode to see a breakdown of a product’s health benefits.
And, of course, there’s the advice you already know: Eat more fruits, vegetables, whole grains, and legumes, and cut down on fatty and sugary snacks. Whether or not scientists prove that UPF is harmful, it’s still a good idea to follow this advice.
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