Why we may never know the truth about ultra-processed foods – BBC News

They are the black beast many nutritionists – mass-produced but appetizing foods like chicken nuggets, packaged snacks, soft drinks, ice cream or even sliced ​​brown bread.

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 of them are considered junk food.

What unites them is their synthetic look and taste, which has made them a target for some clean-living advocates.

There is growing evidence that these foods are unhealthy. But experts can’t agree on exactly how or why they affect us, and it’s not clear whether science will provide an answer anytime soon.

Although recent research shows that many widespread health problems, including cancers, heart disease, obesity and depression, are related at the UPF, there is no proof yet that they are cause by them.

For example, at a recent meeting of the American Society for Nutrition in Chicago, an observational study of more than 500,000 people in the United States was presented. It found that those who consumed the most UPF had about a 10% increased risk of dying, even after adjusting for their body mass index and overall diet quality.

In recent years, many other observational studies have shown a similar link – but that doesn’t mean that how Food processing causes health problems, or it is necessary to determine which aspect of these processes might be responsible.

So how do you find out the truth about ultra-processed foods?

The type of study needed to definitively prove that FPUs cause health problems would be extremely complex, suggests Dr Nerys Astbury, a senior researcher in diet and obesity at the University of Oxford.

It would be necessary to compare a large number of people following two diets – one high in UPF and one low in UPF, but with exactly the same calorie and macronutrient content. This would be extremely difficult to do.

Participants would have to be locked up so that their diets could be closely monitored. The study would also have to include people with similar diets as a starting point. This would be a considerable logistical challenge.

And to counter the possibility that people who consume less UPF may simply have healthier lifestyles, such as exercising more or getting more sleep, participants in the groups should have very similar habits.

“It would be expensive research, but you could see changes relatively quickly through diets,” says Dr Astbury.

Funding for this type of research may also be difficult to obtain. There could be accusations of conflicts of interest, because researchers motivated by these types of trials may have an idea of ​​the conclusions they want to achieve before they begin.

In any case, these trials could not last very long: too many participants would probably drop out of the study. It would be unrealistic to ask hundreds of people to follow a strict diet for more than a few weeks.

And what could these hypothetical tests actually prove?

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 show neither more nor less,” he says. Claims to the contrary are “bad science,” he says.

Another option would be to study the effect of common food additives found in UPFs on a laboratory model of the human intestine – something scientists are currently doing.

There is, however, a larger problem: the confusion surrounding what actually counts as a UPF.

Typically, they contain more than five ingredients, few of which are found 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 eyes, flavor enhancers, colorings, emulsifiers, sweeteners, and glazing agents are added.

They range from the obvious (sugary breakfast cereals, soft drinks, slices of American cheese) to the unexpected (supermarket hummus, low-fat yogurts, some mueslis).

This raises questions: How helpful is a label that puts chocolate bars in the same category as tofu? Could some FPUs 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 goes 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 canned tuna and salted nuts) to UPFs.

The system was developed in response to rising obesity in Brazil, while sugar consumption was falling. Professor Monteiro wondered why. He believes our health is influenced not only by the nutrient content of the foods we eat, but also by the industrial processes used to make and preserve them.

He says he didn’t expect the huge attention UPFs are getting now, but says “it’s contributing to a paradigm shift in nutrition science.”

However, many nutritionists say the fear of FPU 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 confused and afraid of food.

It is true that at present there is no concrete evidence that the way foods are processed is harmful to our health.

Processing is something we do every day: chopping, boiling, and freezing are all processes, and these things are not harmful.

And when food is processed on a large scale by manufacturers, it helps ensure it is safe, lasts longer and waste is reduced.

Take frozen fish fingers, for example. They use up leftover fish, provide healthy nutrition for kids, and save parents time – but they still count as UPF.

And what about meat replacement products like Quorn? Sure, they don’t resemble the original ingredient they’re made from (and therefore fall under Nova’s UPF definition), but they’re considered healthy and nutritious.

“If you make a cake or a brownie at home and compare it to one that comes in a packet with flavour enhancers, do I think there’s a difference between the two foods? No, I don’t think so,” Dr Astbury tells me.

England’s food safety watchdog, the Food Standards Agency, acknowledges reports that people who eat high amounts of UPF have a higher risk of heart disease and cancer, but says it will not take action on UPF until there is evidence that it causes 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 raised some concerns about the practical application of the Nova system in the UK.

For his part, Professor Monteiro is particularly concerned about processes involving intense heat, such as the manufacture of flakes and puffed breakfast cereals, which he says “degrade the natural food matrix.”

He cites a small study suggesting that this leads to a loss of nutrients and therefore leaves us feeling less full, meaning we are more tempted to make up for the shortfall with extra calories.