Ultra-processed food (UPF) is directly linked to 32 harmful effects to health, including a higher risk of heart disease, cancer, type 2 diabetes, adverse mental health and early death, according to the world’s largest review of its kind.
The findings from the first comprehensive umbrella review of evidence come amid rapidly rising global consumption of UPF such as cereals, protein bars, fizzy drinks, ready meals and fast food.
In the UK and US, more than half the average diet now consists of ultra-processed food. For some, especially people who are younger, poorer or from disadvantaged areas, a diet comprising as much as 80% UPF is typical.
The findings published in the BMJ suggest diets high in UPF may be harmful to many elements of health. The results of the review involving almost 10 million people underscored a need for measures to target and reduce exposure to UPF, the researchers said.
The review involved experts from a number of leading institutions, including Johns Hopkins Bloomberg School of Public Health in the US, the University of Sydney and Sorbonne University in France.
Writing in the BMJ, they concluded: “Overall, direct associations were found between exposure to ultra-processed foods and 32 health parameters spanning mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes.”
They added: “Greater exposure to ultra-processed food was associated with a higher risk of adverse health outcomes, especially cardiometabolic, common mental disorders and mortality outcomes.
“These findings provide a rationale to develop and evaluate the effectiveness of using population-based and public-health measures to target and reduce dietary exposure to ultra-processed foods for improved human health.”
Ultra-processed foods, including packaged baked goods and snacks, fizzy drinks, sugary cereals, and ready-to-eat or ready meals, undergo multiple industrial processes and often contain colours, emulsifiers, flavours and other additives. These products also tend to be high in added sugar, fat, and/or salt, but are low in vitamins and fibre.
Previous studies have linked UPF to poor health, but no comprehensive review had yet provided a broad assessment of the evidence in this area.
To bridge this gap, researchers carried out an umbrella review – a high-level evidence summary – of 45 distinct pooled meta-analyses from 14 review articles associating UPF with adverse health outcomes.
The review articles were all published in the past three years and involved 9.9 million people. None were funded by companies involved in the production of UPF.
Estimates of exposure to ultra-processed foods were obtained from a combination of food frequency questionnaires, 24-hour dietary recalls, and dietary history and were measured as higher versus lower consumption, additional servings per day, or a 10% increment.
The researchers graded the evidence as convincing, highly suggestive, suggestive, weak, or no evidence. They also assessed the quality of evidence as high, moderate, low, or very low.
Overall, the results show that higher exposure to UPF was consistently associated with an increased risk of 32 adverse health outcomes, The BMJ reported.
Convincing evidence showed that higher UPF intake was associated with about a 50% increased risk of cardiovascular disease-related death, a 48 to 53% higher risk of anxiety and common mental disorders, and a 12% greater risk of type 2 diabetes.
Highly suggestive evidence also indicated that higher PF intake was associated with a 21% greater risk of death from any cause, a 40 to 66% increased risk of heart disease related death, obesity, type 2 diabetes and sleep problems, and a 22% increased risk of depression.
There was also evidence for associations between UPF and asthma, gastrointestinal health, some cancers and cardiometabolic risk factors, such as high blood fats and low levels of ‘good’ cholesterol, although the researchers cautioned the evidence for these links remains limited.
The researchers acknowledged several limitations to the umbrella review, including that they couldn’t rule out the possibility that other unmeasured factors and variations in assessing UPF intake may have influenced their results.
Some experts not involved in the research also highlighted that much of the research included in the umbrella review was weak and also cautioned that the findings do not prove cause and effect.
However, Dr Chris van Tulleken, an associate professor at University College London and one of the world’s leading UPF experts, said the findings were “entirely consistent” with a now “enormous number of independent studies which clearly link a diet high in UPF to multiple damaging health outcomes including early death”.
“We have good understanding of the mechanisms by which these foods drive harm,” he added. “In part it is because of their poor nutritional profile – they are often high in saturated fat, salt and free sugar.
But the way they are processed is also important – they’re engineered and marketed in ways which drive excess consumption – for example they are typically soft and energy dense and aggressively marketed usually to disadvantaged communities.”
In a linked editorial, academics from Brazil said UPFs were “often chemically manipulated cheap ingredients” and “made palatable and attractive by using combinations of flavours, colours, emulsifiers, thickeners and other additives”.
They added: “It is now time for UN agencies, with member states, to develop and implement a framework convention on ultra-processed foods analogous to the framework on tobacco.”
Meanwhile, a separate study published in the Lancet Public Health suggested that more than 9,000 heart disease-related deaths could be prevented in England over the next two decades if all restaurants, fast food outlets, cafes, pubs and takeaways put calories on their menus.
