'Avoid processed foods' is such a standard bit of advice from health experts and diet promoters that many of us probably don't even hear it anymore.
It's become such a mantra it might be easy to assume we know what that means, but there's a spectrum when it comes to processing, and it's emerging that some 'processed' foods are a lot worse for us than others.
What does 'processed' mean?
Technically, any food that's had something done to it to transform it in some way before it's reached your kitchen is a processed food. Food that's been frozen, canned or bottled is all a type of processed food. So are fermented foods; dried foods; cereals; soups; dairy products… most things that come in packets are processed.
Does that mean everything from a packet is bad?!
No! Most of us don't have the time or inclination to grind our own flour or mill our own grain, let alone make our own bread. There's a wide range of healthy foods that come in packets, and a wide range of processing that can be done to render that food both safe to eat - important, again, if we don't want to be shopping for food every day - and convenient in our busy lives. There's a spectrum when it comes to processing, and it's worth understanding this so we don't get too stressed when shopping.
What are the less healthy processed foods?
Experts agree we should be wary of what are known as Ultra Processed Foods (UPFs). The term describes foods that have been through industrial processing to such a degree that it results in energy-dense products that are also nutrient-poor and high in sugar, unhealthy fats and salt.
Attempts have been made in the public health community to come up with an official definition of ultra-processed foods. One is the NOVA food classification system, devised by researchers in Brazil, which uses this: 'industrial food and drink formulations made of food-derived substances and additives, often containing little or no whole foods'.
That's not a bad definition. For us non-academics, though, it can be easier to think of UPFs as foods that are quite far from the original whole food they're made from, that are also pretty low in nutrition.
"It's often the foods where you can't tell what the ingredients are, or they look nothing like the raw ingredients that went into them," says nutrition researcher Dr Sally Mackay, co-chair of the Food Expert Panel of Health Coalition Aotearoa.
"So something like bread is very familiar, you tend to know that it's got wheat in it. But something like Nutrigrain cereal - you're guessing what grains are in there."
Mackay says there's nuance among UPFs.
"This is a really big group of foods, and it contains things like Vogel's bread that people would not necessarily think were ultra-processed."
Some of these foods are part of most of our diets, Mackay says.
"The reality is that people will always eat ultra-processed foods. It's really hard to have a diet without them. But we would really like to steer people away from the very ultra-processed foods, compared to the ones that maybe they can include as part of a healthy diet."
Take yoghurt, for example: it can be minimally processed, with just milk and culture added. Or it can be ultra-processed, containing extra sugar, flavours, thickeners, syrups and other additives. Cereal can be wholegrain oats, or it can be oats that have been ultra-processed: smushed up by a machine, extruded, refined and formed into new shapes with lots of added ingredients. The nutrition information when you compare the two foods will be quite different.
Why are ultra-processed foods so bad for us?
How long have you got? There are a few reasons.
UPFs tend to be energy-dense and nutrient-poor. The processing has robbed them of the nutrients that might be found in the original ingredients. They often have added sugar, salt and fat, and often contain unhealthy trans fats. They almost always contain other additives as well, such as flavourings, colourings and preservatives.
UPFs are easy to overeat - and they've been designed that way. Because of all those tasty extras, UPFs are highly attractive and palatable. That makes them really easy to over-consume. It also means they're good at displacing other healthy foods in the diet - in other words, when we eat them, we're likely to eat less healthy and filling whole or minimally-processed foods.
UPFs are typically low in fibre, sometimes because the nutritious parts of the original ingredient - like the fruit flesh or the outer layer of the grain, for example - have been removed during processing of the food.
Lastly, UPFs are cheap to produce so they're highly profitable. They are sometimes marketed aggressively at the most vulnerable groups, such as children. That's something Mackay's Health Coalition is calling for regulation against, which seems wise given that UPFs have been found to make up as much as half of the energy in the diets of toddlers in Aotearoa.
All of these properties are likely contributors to poor health. Research on UPFs has found associations between high intakes of ultra-processed foods and higher risks of obesity, heart disease, stroke, type 2 diabetes, cancer, frailty, depression and premature death.
UPFs are also linked to weight gain, with one interesting laboratory trial finding that when offered an ultra-processed diet, people ate about 500 calories (2,100 kilojoules) more per day than they did on a minimally processed diet, and gained almost a kilo on average in just two weeks as a result. When they were on the minimally processed diet, they lost about the same amount of weight.
What's the best advice for minimising UPFs in our lives?
"When you look at the shelves, 69 percent of the foods are ultra-processed. It's pretty hard to avoid them," Mackay says.
She points to "those highly extruded snacks" as some of the worst of the worst UPFs.
"Someone at work the other day offered me a packet of something… And I looked at it and thought, I have no idea what you've just offered me. It's this sort of round puffy, beige thing. And I don't know what it's made from. I had no clue."
Mackay suggests a healthy approach is about balancing UPFs with whole foods, and looking at all foods in context of the bigger picture.
"If you can recognise where the food comes from or where the ingredients come from, that's a good start. Choose more minimally-processed foods where you can, but it's okay to add some processed foods and ultra-processed foods for convenience and flavour.
"But if a lot of your everyday foods are minimally processed, then that's obviously better for your health."
RNZ
