Once upon a time they were a treat, but consumed habitually in excess, ultra-processed foods have become toxic.
Two large studies, published today in the British Medical Journal (BMJ), have found consistently eating too many “ultra-processed” foods are associated with a significantly greater risk of cardiovascular disease and premature death.
Many of the packaged foods on our supermarket shelves are made “hyper-palatable” through chemical processing and “cosmetic” enhancement, like the addition of colours, flavours and emulsifiers. High in added sugar, fat, and/or salt but with little if any nutritional value, they include confectionery snacks, fizzy drinks, cakes, sports drinks, many breakfast cereals, pastries, dehydrated vegetable soups, and reconstituted meat and fish products.
Globally these foods are believed to account for up to 60 per cent of daily energy intake (in Australia they account for about 35 per cent) and are already associated with obesity, high blood pressure and cholesterol as well as some cancers.
The first new study of 105,159 French adults, spanning 10 years, measured cardiovascular disease rates against the dietary intake of ultra-processed foods (3000 different foods on the questionnaires were grouped according to their level of processing).
The researchers found that a 10 per cent increase in the amount of ultra-processed foods in the diet was associated with a significantly higher likelihood of ending up with cardiovascular disease, coronary heart disease, and cerebrovascular disease (increases of 12, 13 and 11 per cent respectively).
Those with a diet high in unprocessed or minimally processed foods, on the other hand, were significantly less likely to end up with any of these diseases.
The authors, who noted that the study was observational and who adjusted for variables, suggested there may be several explanations for the results.
It could be the heavy load a diet high in fat, sugar, salt and devoid of nutrients places on the body. It could also be the lack of fruits, vegetables and other nutrient-rich foods.
But, it’s not just the nutrients or lack-thereof having an impact. The authors point out that the cumulative and cocktail effects of eating different processed foods "remain largely unknown”. They suggest that certain food additives may adversely effect cardiovascular health and that certain processing techniques may also be having a detrimental effect on our health.
A study published last week seems to strengthen this idea. It found that participants on an ultra-processed diet gained weight, while participants on a minimally processed diet that contained the same amount of salts, fats and sugars and calories did not.
The second BMJ study, of nearly 20,000 Spanish adults over the course 10 years, also grouped foods according to their level of processing. This time however, the researchers were looking at premature death by any cause.
They found that eating more than four servings of ultra-processed foods a day (which is pretty easy when you consider that one serving of French fries is about 12 to 15 potato sticks) was associated with a 62 per cent increased risk of premature death by any cause, compared with less than two servings per day.
“Moreover, each additional serving of ultra-processed food was associated with a statistically significant 18 per cent higher hazard of all cause mortality,” the paper’s authors said.
Public Health nutritionist, Doctor Rosemary Stanton says the results of these two studies “fit very well” with the growth of diet-related health problems in recent decades.
“All these increased as diets changed to eating ready-made foods rather than home-cooked foods,” she says. “For example, I have estimated that in the 1960s (before supermarkets became widespread), Australians had 600-800 foods available – very few ultra-processed. Now we have the average supermarket stocking more than 30,000 items – many ultra-processed.”
She agrees that the reason ultra-processed foods have a deleterious effect on health is complex .
“Is it the composition of the foods? Or the industrial processing? Or the fact they are consumed instead of healthy foods? Or the fact that they can be eaten quickly? Or the fact that if you consume an equivalent weight of food, you will take in more calories?” she asks.
“My conclusion is that all these factors may be relevant and putting problems down to a single factor may be delaying the solution to obesity and diet-related health problems.”
Mark Lawrence, a professor of Public Health Nutrition at Deakin University’s Institute for Physical Activity and Nutrition, agrees.
“There is a message in there that I think is new,” he says. “We need to stop focusing excessively on nutrients and thinking so long as we take care of the nutrients in our diets it’ll be healthier. These [studies] challenge that as too simplistic. It’s more than just how much saturated fat or whatever in the diet, it’s also about the extent of processing.”
For instance, he says that re-formulating foods to lower the amount of salt, sugar or fat often means increasing the amount of processing (like adding artificial sweeteners to reduce total sugars in a product).
While processing itself isn’t “bad”, Lawrence says it becomes so “when the extent of it is so extreme.”
It’s “quite plausible” that the way these foods have been physically or chemically changed is their main problem, says Lawrence: “I think that’s a really interesting concept.”
The message, according to Lawrence: “Eat less ultra-processed food and more unprocessed or minimally processed food.”