ULTRA-PROCESSED FOODS

A new dietary demon has entered the psyche: ultra-processed food (1). ‘Ultra’ implies extreme, like ultra-luxury resorts. In this case, it’s applied to foods that aren’t simply processed – they also contain ingredients not available to the average cook. By definition, ultra-processed foods contain cosmetic additives: flavours, colours, emulsifiers, modified starches and other substances that are deliberately added by manufacturers. In Australia, New Zealand and many other countries around the world, food additives are regulated by law. They must pass safety testing and be approved by CODEX Alimentarius (2). They can be used only under specified conditions: particular foods, specific purposes and in limited quantities.

According to some research, these additions make them harmful, perhaps by encouraging you to overeat – although no mechanism has been identified (3). Ultra-processed food specifically excludes processed foods with chemical preservatives (4). After all, this prevents food spoilage and food poisoning – a good outcome – although most people remain ignorant of this.

The term ‘ultra-processing’ was introduced in 2009 by Professor Carlos Monteiro and colleagues at the University of Sao Paul in Brazil (5). It was the 4th component of a classification of foods based on level of processing. The first level was minimally processed (think frozen fruit and vegetables), the second level was made up of common food ingredients that we use in the kitchen (think sugar, butter, flour) and the third level of foods produced in factories – including bread, cheese, canned goods and every convenience food under the sun. A bread is not ultra-processed unless it contains one of the cosmetic additives, such as an emulsifier to inhibit staling.

Food processing has been present for at least half of our 4 million years of evolution. At the start, all food was raw – fruit, leaves, some honey, insects, an occasional animal. It was a tough diet, requiring big teeth, powerful jaws and hours of chewing and digestion. Over evolutionary time, our mouthparts and gut became smaller, presumably because our diet became easier to digest and more nutrient dense. Early hominins discovered they could bash animal bones with a handy rock to extract the marrow – pure fat – 9 Calories (37 kilojoules) per gram (6). When we mastered fire, about 1 million years ago, cooking gave us access to starch in underground storage organs (yams and potatoes) and legumes (lentils, etc…). These are all toxic in the uncooked state. This new form of processing – cooking – transformed human diets, selecting for individuals with more salivary amylase and higher AMY1 copy number (7).
Fast forward to about 100,000 years ago (one minute ago on the hominin clock), we see the first grindstones in the archaeological record. Seeds were now being ground into flour, mixed with water and baked (8). Indeed, Australia’s first people may have been the first bread bakers (9). When the last glacial period gave way to a warmer, wetter climate about 10,000 years ago, we decided to grow our own food – the Neolithic Revolution. Seeds could be harvested and stored all year round.

We like to think the last 2000 years of human existence is the ‘norm’, but it was far from it. Most people in Europe were peasant farmers and villagers who often did not have enough food. Thinness was not by choice. Foods were highly seasonal and came in gluts – much of it spoiled before it was eaten. The only people who appeared to be overweight were kings, queens, clergy and the wealthy. None of their foods was sold by multi-nationals or ultra-processed, but it was abundant, even in monasteries.

When Marco Polo trafficked goods from East to West in the 13th century, he opened up a lucrative trade in herbs and spices – the cosmetic food additives of the times. They were highly sought because food gluts mean a monotonous diet. Herbs and spices allowed food adultery on a mass scale – spoiled food to be disguised. Spices weren’t exactly safe in themselves. Even today, spices and dried herbs carry a heavy load of thermophilic spores that can be dangerous under certain conditions (10).

When fruit and vegetables were bottled at home, sterility was far from certain. The consequences could be catastrophic because microbes like Clostridium botulinum produce botulinum toxin which is lethal in 1 part per billion. Today, commercial sterility in canned foods is guaranteed so that no live organisms will be present. We should be grateful – our modern food system gives us access to the most abundant, varied, microbiologically-safe food supply in human history. And it’s delicious.

Monteiro and other researchers assume that UPFs are the most palatable group and more conducive to overeating than processed foods. In fact, Rogers and colleagues proved otherwise – the most desired foods are not UPF – they are those with a 50:50 ratio of carbohydrate to fat calories – cosmetic additives are irrelevant (11).

There’s no doubt that we are all tempted by foods that are highly palatable and ‘in our face’, some healthier than others. Is education the key? Many authorities think so, but not all agree (see this month’s PERSPECTIVES). Front-of-pack labelling, like health stars or traffic lights, might do the trick. But when it comes to the next generation of children and adults, we take a hit-and-miss approach, recommending food supplements. One in two pregnancies are still unplanned and the first few weeks of brain development are left to chance. Learning difficulties are common. We should ask ourselves if this is the best we can do?

So why demonise so-called “ultra” processed foods for the simple reason that they contain safe and approved additives? If they are not nutritious by virtue of their added sugar, saturated fat and salt content, it doesn’t matter whether they are made at home versus a factory. The chemical and physical changes – the levels of processing – are often identical. In my opinion, it is neither logical nor scientific to distinguish foods according to the NOVA classification.

Read more:

1. UK NHS. What are processed foods? June 2023.
2. FAO/WHO Food Standards Programme. Codex Alimentarius.
3. Juul and colleagues. The role of ultra-processed food in obesity. Nat Rev Endocrinol, 2025.
4. Monteiro and colleagues. The UN Decade of Nutrition, the NOVA food classification and the trouble with ultra-processing. Public Health Nutrition, 2018.
5. Monteiro. Nutrition and health. The issue is not food, nor nutrients, so much as processing. Public Health Nutr, 2009.
6. Ben-Dor and colleagues. Man the Fat Hunter: The Demise of Homo erectus and the Emergence of a New Hominin Lineage in the Middle Pleistocene (ca. 400 kyr) Levant. PLOS ONE, 2011.
7. Wrangham. Catching Fire: How Cooking Made Us Human. Basic Books, 2009.
8. Mercader. Mozambican Grass Seed Consumption During the Middle Stone Age. Science, 2009.
9. Hayes and colleagues. 65,000-years of continuous grinding stone use at Madjedbebe, Northern Australia. Sci Rep, 2022.
10. Mathot and colleagues. Bacterial spores in spices and dried herbs: the risks for processed food. Compr Rev Food Sci Food Saf, 2021.
11. Rogers and colleagues. Nutrient clustering, NOVA classification, and nutrient profiling: How do they overlap, and what do they predict about food palatability? Appetite, 2024.

Emeritus professor Jennie Brand-Miller held a Personal Chair in Human Nutrition in the Charles Perkins Centre and the School of Life and Environmental Sciences, at the University of Sydney until she retired in December 2022. She is recognised around the world for her work on carbohydrates and the glycemic index (or GI) of foods, with over 300 scientific publications. Her books about the glycemic index have been bestsellers and made the GI a household word.