Welcome to Nutrition Bites. The no nonsense podcast where you get the truth about food so you can eat what you want and be healthy. I’m your host Maggie and welcome to the series! Processed foods are a controversial topic. On one hand they are often seen as unhealthy, while on the other, necessary and unavoidable. It can be a confusing space so where should you stand? On the menu today, the ultra-processed debate.
Industrial processing has long helped to improve the shelf-life and stability of food, allowing it to be consumed out of season, reach far away places, and stored without refrigeration. Food processing also enhances taste and texture. Without it we wouldn’t have magical creations like Cool Ranch Doritos, mango mochi, or even french fries! Processing is not just used for treats and indulgences - it’s also necessary for many of our staples like canned tomato soup, vanilla yoghurt, and cereal. Without knowing, many of your weekly groceries are likely highly or ultra processed, that is, manufactured with additives and little whole ingredients. But because processing can alter the nutritional properties of food, health scientists, and governments are concerned. After all, it’s more likely that we purchase highly-processed pasta sauce with added sugar and salt, rather than make it from scratch like nonna would want. At the same time, nonna had the whole day to simmer tomatoes and we now spend our time “circling back” at work. Our modern world necessitates the inclusion of processed foods, and many view them as necessary to help feed a growing world in an environmentally sustainable way. But should health agencies advise us to moderate our intake like they do with alcohol? It’s not an easy answer, and exactly why ultra-processed foods are at the centre of the latest nutrition debate. Let’s get into it.
The “Great Debates in Nutrition” is a recurring series published in the American Journal of Clinical Nutrition - one of the leading scientific publications in the field. Think of this journal like the HBO of TV channels and this debate series like a UFC fight night but for nutrition nerds. Leading researchers use this opportunity to hurl academic insults at one another such as “his assertion is erroneous”. Big burn right there. Now before introducing our contenders, and pledging your allegiance to a side, let’s better understand what is being debated and why.
The NOVA food classification system, designed by scientists at the University of Sao Paulo, was created to help categorise foods and drinks based on the nature and extent of their processing. Four groups exist. Group one includes unprocessed items such as raw produce, nuts, and meat, as well as minimally processed foods with no added ingredients, like frozen fruits and veg, pasteurised milk, 100% juice, and plain yoghurt. Group two covers processed ingredients, such as oils, butter, vinegar, sugar and salt. Group three are the “processed” foods, which I like to think of as the “1800s housewife” group. You know things you could make at home if you had no external job and the internet didn’t exist. Items include cheese, fresh bread, cured meat, salted nuts, canned fruit, beer and wine.
The final category in this system is ultra-processed foods, abbreviated as UPFs. UPFs contain ingredients that you do not have access to when making homemade food. They often contain industrial additives, are made with little whole food ingredients, are packaged, and have plenty of added sugar, fat and salt. Familiar basics such as deli meats, standard grocery store breads and salad dressings, belong to this group, as do the more recognizably industrial items such as store-bought muffins, pop, frozen meals and most fast food. Importantly, many vegetarian and vegan alternatives are also UPFs like Beyond meat, coconut yoghurt and oat milk.
As you can imagine, UPFs easily make up a big part of our diet, especially in wealthier nations. In the UK and US, over 50% of calories consumed come from UPFs, and for American teens it’s two thirds. Unfortunately, a wave of new research suggests that a diet high in these items is bad for our health. So as a result, governments around the world are considering including recommendations against UPFs in their dietary guidelines. Which brings us to the debate.
In June of this year the Great Debates in Nutrition series posed the following question: should the categorization of UPFs be used to help inform dietary guidelines. In favour of this position is Carlos A Monteiro - a Professor of Nutrition and Public Health at the University of Sao Paolo and inventor of the NOVA food categorization system. He’s also a member of the WHO’s Nutrition Expert Advisory Group on Diet and Health and a group on Ending Childhood Obesity. As indicated by his lively Twitter feed, Monteiro is a notorious advocate against UPFs.
His opponent in this matchup is Arne Astrup, a Program Director at the Novo Nordisk Foundation, in Denmark, and professor of nutrition at the University of Copenhagen. Having obtained my own Masters in Nutrition at this University, I can say with assertion that Astrup is the G.O.A.T of nutrition in Denmark. He’s associated with a whopping 2000 scientific publications, and is one of the most recognized voices in the field. Astrup is also notorious for being on advisory boards of pharma companies, supplement companies, food lobbyist groups, and organisations such as the Dutch Beer Institute, Nestlé, and Weight Watchers. So it’s no surprise he is arguing against the use of UPFs in dietary guidelines. Ok. Now that we know why this debate is important and who our conentenders are, let’s get ready to academically rumble.
Starting off with the anti-big-food and probably not the guy you want to invite over for a Superbowl potluck, Monteiro outlines three main arguments in his case for the inclusion of UPFs to inform dietary guidelines. One, there is significant evidence to show that consuming UPFs leads to a poor diet. Two, UPFs are associated with developing chronic disease. And three there are reasonable mechanisms to explain this link.
Monteiro starts by providing evidence from various studies which show that the more UPFs someone eats, the more calories, added sugar, salt and saturated fat they consume. Not only that, but they also tend to consume less fibre, protein, and micronutrients. And that’s likely because research also shows that when intake of UPFs increases, consumption of fruits, veggies, and legumes, you know - the good stuff, decreases.
Building off of this, Monteiro then points to thirty observational studies which associate a diet high in UPFs with the development of chronic diseases like obesity, type two diabetes, hypertension, cancer, and depression. A logical result considering that a nutritionally unbalanced diet is associated with these diseases. Monteiro also highlights a short clinical trial where ten adults consumed a diet high in UPFs, while ten others ate a nutritionally equivalent diet but with less processed foods. Despite the nutrient profiles being the same, the UPF diet group gained significantly more weight after only two weeks.
Monteiro’s final argument involves the mechanism of action. Scientists can’t just state X causes Y without also explaining how that happens. In the case of UPFs and disease development he argues that in addition to their poor nutrition, the structural changes of these foods make them quick to digest, which delays satiation and can lead to overconsumption and weight gain. Similar structural changes can also disrupt our gut microbiota, which impacts so much of our health. In addition the absence of health-protective compounds, like phytochemicals found in fruits and veg, may put us at greater risk of certain cancers. And finally, UPFs are designed to be addictive, which causes us to overeat. I mean, the tagline “Once you pop you can’t stop” is Pringles practically rubbing it in our faces that their moustache-sporting mascot, who I just learned is called Julias Pringle, has us wrapped around his cartoon finger.
In subtle defence of Julias, and a lot of other UPFs, Astrup's main argument against the use of UPFs to inform dietary guidelines is simple: we don’t have enough evidence to establish causality. And when governments make recommendations without robust scientific evidence, we can get in trouble. A historic example which underscores this point is the 1990 US Dietary Guidelines which advised Americans to avoid excess fat consumption. Back then, people actually trusted scientists and the government, thus ushering in the infamous low-fat era, and a steep increase in carbohydrate consumption. A decade later, the government reversed their advice and shifted the blame for weight gain to carbs instead of fat. Astrup warns that to make scientifically sound recommendations you need to establish causality. And to do that four things are required: a precise definition, a plausible mechanism, support from observational research, and confirmation from clinical trials.
Astrup begins by claiming the definition of UPFs is too ambiguous - a not-so-sutble dig at his opponent, the actual creator of this definition. He questions why additives like pectin, which are naturally found in apples, are treated the same as more industrially produced ingredients? He also states that the degree of processing affects nutrients differently. The protein in a UPF like salami is metabolised similarly to the protein in steak. Whereas the body reacts differently to carbohydrates in a UPF like pop (where we can get a hefty blood spike), than carbs in a minimally processed food. Simply put, UPFs are diverse and we shouldn’t treat them the same.
For his second argument, Astrup disagrees with Monteiro’s explanation of why UPFs lead to chronic disease. He believes that it’s the nutrition profile of the UPF, not anything else, that’s the link. Astrup does agree that diets high in calories, saturated fat, added sugar, and sodium can lead to poor health, but he notes that we already use this knowledge to inform guidelines. From his perspective, there is no mechanism unique to UPFs that links them with chronic disease.
For his closing argument, Astrup argues that the many observational studies which link UPFs and poor health only show correlation, not causation. After all, how can we say for certain that it is a high UPF diet that causes obesity, and not a diet low in fruits, veggies and legumes? Astrup also argues that the absence of large clinical trials further demonstrates a lack of causal evidence in this space. So in conclusion, what we currently use to inform dietary guidelines (the whole too much sugar + excess calories is bad, more fruit & veg is good), is enough, and considering UPF classification is pointless.
Now before you declare yourself Team Monteiro or Astrup, a choice some may say is akin to Team Jacob vs Edward, I do want to mention a few points I personally feel were missed. Any time there is a discussion around dietary guidelines, we should also consider the socioeconomic factors and systemic reasons behind why people make food choices. The convenience and lower cost of UPFs can be a lifesaver to cash and time-strapped people. Good luck telling a stressed out student, burnt out worker, or emotionally drained parent that they should always be baking their bread from scratch. UPFs are also important for folks without consistent access to kitchens, and for those with difficulty cooking due to disability or injury. UPFs can also help the general population cut back on their environmental footprint. It’s difficult enough getting people to reduce meat and dairy consumption, now you want to discourage them from soy-based sandwich meat and almond milk? I completely agree that the nutritional profile of many ultra processed foods is…pretty bad, but they do serve a purpose. And whenever we guide people to eat in a certain way we have to make sure that those recommendations are realistic and achievable.
I also want to dive into the evidence argument, specifically Astrup’s desire for clinical trials. While I agree that observational studies show correlation not causation, there is a good reason why clinical trials can be so difficult to conduct in this space. It’s unethical to run an experiment where one group is likely to be harmed, even if that harm is a few excess pounds and higher cholesterol. Considering that many UPFs have a poor nutritional profile, it’d be hard to get approval for multiple massive clinical trials testing out if they cause health issues. Fortunately, we do have a couple of citizen scientists who’ve kind of already tested this for us.
Back in 2004 the film Super Size Me was released - you know the one. This American documentary followed director Morgan Spurlock on a 30-day McDonald’s-only adventure. After his McBinge, Spurlock revealed he had gained 24 pounds, raised his cholesterol to unhealthy levels, and experienced mood swings. While great for views, and as a staple of the public school health curriculum, it’s not a realistic diet to evaluate. A more recent, and true-to-life, experiment however was filmed for the BBC in 2021. In this documentary, Dr. Chris Van Tulleken dove into a month-long experiment where he upped his usual intake of UPFs from 30% of his diet to 80%. This new diet reflects the standard for one in five UK adults. After it was over, Van Tulleken revealed he had gained 15 lbs, felt addictive drives to overeat, had trouble sleeping, and a poor mood. And while I know that anecdotes are not scientific evidence, these two rogue experiments do reflect the unethical potential of conducting clinical trials in this field.
Alright, now let’s get back to the scoreboard. Astrup’s main argument against the inclusion of UPFs in dietary guidelines is that the association between these products and ill health is that we don’t have enough evidence. And from the evidence we do have, we can’t conclude that chronic disease development is because these foods are processed, versus because of their poor nutrition profile. And importantly, the information we use to currently advise these guidelines already takes nutrient composition into consideration. On the flip side, Monteiro argues that the poor nutrition profile of these foods are inherent characteristics of UPFs, and that other factors, and mechanisms, also link these foods to an increased risk of disease. Now both sides exhibited compelling arguments, but ultimately I must crown Monteiro the nutrition-smackdown champ - and here’s why.
At the end of his written argument Monteiro states that Astrup desires “absolute” proof that UPFs cause disease, however we don’t have the luxury of waiting for that evidence before making public health decisions. He references Austin Bradford Hill, the English epidemiologist who demonstrated the connection between cigarette smoking and lung cancer. Hill stated that part of scientific advancement is knowing that we always stand to gain more, while at the same time not ignoring the knowledge we have now. So if patterns from dozens of global observational studies show high UPFs are linked to poor health, and that these foods are increasingly making up more and more of our diets, well then why not take action now?
Without having the formal language to describe it, I’ve long tried to eat as few UPFs as possible. Now I never ventured into the purist clean eating territory, but I’ve long advocated for making my own salad dressings and pasta sauces, and at a certain time in the pandemic, my own bread. Controlling what goes in my food allows me to make better choices about what I eat. That said, I also believe that there is a place for UPFs in our diet, and that not all of these foods and drinks are addictive willy wonka-esque creations. As someone who tries to eat as planet-friendly as possible, UPFs like oat milk and frozen veggie burgers are a staple in my kitchen. But still, I agree with Monteiro that eating fewer of this calorically dense, and sugar and salt-laden foods, is probably best for public health. And I personally can’t think of any harm done if governments and health agencies recommend people to eat less of these things. That is unless Julias Pringle, and his gang of anthropomorphized mascots come to life, fuelled with rage by a downturn in sales. But if that somehow becomes a reality, well we have much larger issues to face. That’s been the bite for today, stay hungry.