Ultra-processed foods (UPF) have been directly linked to 32 harmful health effects, 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 of the first comprehensive 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 of the average diet now consists of ultra-processed foods. For some, especially people who are younger, poorer or from disadvantaged areas, a diet consisting of as much as 80% UPF is typical.
The findings published in the BMJ suggest that diets high in UPF may be detrimental to many elements of health. The results of the review, which involved nearly 10 million people, highlighted 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 USA, the University of Sydney and the 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 foods was associated with a higher risk of adverse health outcomes, particularly cardiometabolic, general mental disorders and mortality.
“These findings provide a rationale for developing and evaluating 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, sodas, sugary cereals, and ready-to-eat or prepared meals, undergo various industrial processes and often contain colors, emulsifiers, flavors, and other additives. These products also tend to be high in added sugar, fat and/or salt, but are low in vitamins and fiber.
Previous studies have linked UPF to poor health, but no comprehensive review has yet provided a broad assessment of the evidence in this area.
To bridge this gap, researchers conducted an umbrella review—a high-level evidence summary—of 45 separate pooled meta-analyses from 14 review articles associating UPF with adverse health outcomes.
The review articles were all published in the last 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% increase.
The researchers graded the evidence as convincing, highly suggestive, suggestive, weak or no evidence. They also rated the quality of evidence as high, moderate, low or very low.
Overall, the results show that higher exposure to UPF is consistently associated with an increased risk of 32 adverse health outcomes, The BMJ reported.
Convincing evidence has shown that higher UPF intake is associated with approximately a 50% increased risk of cardiovascular disease-related death, a 48 to 53% higher risk of anxiety and general mental disorders, and a 12% increased 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 that the evidence for these links remains limited.
The researchers acknowledged several limitations of the umbrella review, including that they could not rule out the possibility that other unmeasured factors and variations in the assessment of UPF intake may have influenced their results.
Some experts who were not involved in the research also highlighted that much of the research included in the umbrella review was weak and also warned that the findings did 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 that have shown a diet high in in UPF clearly links to multiple adverse health outcomes including early death”.
“We have a good understanding of the mechanisms by which these foods cause harm,” he added. “This is partly due to 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 are designed and marketed in ways that drive excess consumption – for example, they are typically soft and energy-dense and aggressively marketed usually to disadvantaged communities.”
In a linked editorialacademics from Brazil said UPFs are “often chemically engineered cheap ingredients” and “made palatable and attractive using combinations of flavors, colors, 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.
