Highly suggestive (class II) evidence indicates that higher exposure to ultra-processed foods is associated with an increased risk of 32 damaging health outcomes including cancer, major heart and lung conditions, mental health disorders, type 2 diabetes and obesity, as well as all-cause mortality, according to an international team of researchers.
The findings show that diets high in ultra-processed food may be harmful to many body systems and underscore the need for urgent measures that target and aim to reduce dietary exposure to these products and better understand the mechanisms linking them to poor health.
Ultra-processed foods, including packaged baked goods and snacks, fizzy drinks, sugary cereals, and ready-to-eat or heat products, 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. They can account for up to 58% of total daily energy intake in some high-income countries and have rapidly increased in many low and middle-income nations in recent decades.
Many previous studies and meta-analyses have linked highly processed food to poor health, but no comprehensive review has yet provided a broad assessment of the evidence in this area. To bridge this gap, researchers carried out an umbrella review of 45 distinct pooled meta-analyses from 14 review articles associating ultra-processed foods with adverse health outcomes.
The review articles were all published in the past three years and involved almost ten million participants. None were funded by companies involved in the production of ultra-processed foods.
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 ultra-processed foods was consistently associated with an increased risk of 32 adverse health outcomes.
Convincing evidence showed that higher ultra-processed food intake was associated with around a 50% increased risk of cardiovascular disease-related death, a 48-53% higher risk of anxiety and common mental disorders and a 12% greater risk of type 2 diabetes.
Highly suggestive evidence also indicated that higher ultra-processed food intake was associated with a 21% greater risk of death from any cause, a 40-66% increased risk of heart disease-related death, obesity, type 2 diabetes, and sleep problems, and a 22% increased risk of depression.
Evidence for the associations of ultra-processed food exposure with asthma, gastrointestinal health, some cancers and cardiometabolic risk factors, such as high blood fats and low levels of "good" cholesterol remains limited.
The researchers acknowledge that umbrella reviews can only provide high-level overviews and they can't rule out the possibility that other unmeasured factors and variations in assessing ultra-processed food intake may have influenced their results. However, their use of rigorous and prespecified systematic methods to evaluate the credibility and quality of the analyses suggests that the results withstand scrutiny.
“This umbrella review reports a higher risk of adverse health outcomes associated with ultra-processed food exposure. The strongest available evidence pertained to direct associations between greater exposure to ultra-processed foods and higher risks of all cause mortality, cardiovascular disease related mortality, common mental disorder outcomes, overweight and obesity, and type 2 diabetes,” the researchers concluded. “Evidence for the associations of ultra-processed food exposure with asthma, gastrointestinal health, some cancers, and intermediate cardiometabolic risk factors remains limited and warrants further investigation. Coupled with existing population based strategies, we recommend urgent mechanistic research and the development and evaluation of comprehensive population based and public health strategies, including government led policy frameworks and dietary guidelines, aimed at targeting and reducing dietary exposure to ultra-processed foods for improved human health.”
The findings were reported in the paper, ‘Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses’, published in The British Medical Journal. To access this paper, please click here