by “Our study showed a relatively consistent trend in the link between higher intake of ultra-processed foods and a number of adverse health outcomes,” says lead author Melissa Lane, PhD, a postdoctoral research fellow and professor at Deakin University in Melbourne, Australia.
The review highlights the need for public health strategies to reduce the amount of ultra-processed food people eat and more research to understand their potential negative impact on health, according to Dr Lane .
Ultra-processed foods can make up almost 60 percent of the Western diet
Ultra-processed foods include mass-produced products that require industrial formulations, such as sugar-sweetened beverages, packaged baked goods and snacks, sugary cereals, and ready-to-eat or microwave products. They often contain added artificial colors and flavours, as well as high levels of added sugar, fat and salt, but contain few nutrients, vitamins or fibre.
For people in wealthier countries, ultra-processed foods can account for up to 58 percent of calories consumed each day, according to researchers.
Although there have been many studies on how highly processed foods affect health, this is the first comprehensive review to look at all the evidence that has accumulated since 2009, the year the concept of ultra-processed foods was introduced. in research. The most recent meta-review included 45 separate pooled meta-analyses from 14 review articles.
All of the review articles were published over the past three years and involved nearly 10 million participants. None of them were funded by companies involved in the production of ultra-processed foods.
All analyzes included observational studies, not randomized controlled studies. That means the researchers didn’t design a trial where some people ate ultra-processed foods and compared them to people who didn’t. Instead, the studies typically recorded estimates of exposure to ultraprocessed foods from a combination of food frequency questionnaires, 24-hour dietary recalls, and dietary histories. The participants were then grouped between higher versus lower consumption, an additional serving per day, or 10 percent increments.
The researchers graded the included studies as strong, highly recommended, suggestive, weak or no evidence. They also used the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) system to rate the quality of evidence for each pooled analysis as high, moderate, low, or very low. According to the GRADE approach, all observational studies are initially considered to be of low quality.
Ultra-Processed Foods Linked to Higher Risk of Heart Disease and Anxiety
According to the authors there was “convincing evidence” that a higher intake of ultra-processed food was associated with:
- Close to a 50 percent increased risk of heart disease-related death
- 48 to 53 percent higher risk of anxiety and common mental disorders
- 12 percent greater risk of type 2 diabetes
“Highly suggestive” evidence also showed that higher ultra-processed food intake was associated with:
- 21 percent greater risk of death from any cause
- 40 to 66 percent increased risk of death related to heart disease, obesity, type 2 diabetes, and sleep problems
- 22 percent increased risk of depression
The evidence for 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 and more research is needed in these areas, of according to the authors.
“The analysis is an umbrella review, so basically an attempt to summarize the data that is currently available. A strict interpretation of the quality of evidence (GRADE) data would suggest that there is only very limited evidence for an association between ultra-processed food intake and health, as most associations are rated as low or very low quality. ,” says Gunter Kuhnle. , PhD, professor and researcher in the department of food and nutrition sciences at the University of Reading in England, who was not involved in the study.
The authors do not seem to agree with this – although they do not explain the reasons for it – and consider these associations relevant enough to be discussed, says Dr Kuhnle. “But they agree that the study cannot provide any information on causality,” he says.
Why Are Most Nutrition Studies Observational?
The researchers acknowledge that reviews such as this one “can only provide a high-level overview” and that other unmeasured factors and variations in assessment of ultra-processed food intake may have influenced their findings.
However, the fact that the observational analyzes were included does not rule out the potential associations, especially as more data become available in the future, the authors wrote. They also point out that 93 percent of the pooled analyzes of the increased risks reported in the review had very similar results.
“These findings support urgent mechanistic research and public health actions that seek to target and minimize ultra-processed food consumption for improved population health,” say the authors.
Why Are Ultra-Processed Foods Bad For Us?
They are formulas of cheap ingredients that are often chemically manipulated like modified starches, sugars, oils, fats, and protein isolates, and “there is no reason to believe that people can completely adapt to these products,” a wrote Dr. Monterio.
Do the potential health risks of ultra-processed foods go beyond their link to being overweight or obese, which is known to increase the risk of many chronic conditions?
Obesity is just one harmful outcome of diets high in ultra-processed foods, says Lane. “While a high body mass index may be a precursor biological or physical mechanism linking diets high in ultra-processed foods to other health outcomes, we know that the relationship between unhealthy diets and, for example , mental health outcomes such as depression. body weight,” she says. The impact of these types of food on all of our body systems, including the immune system and gut microbiome, needs to be explored more, says Lane.
More Research Is Needed to Understand the Health Risks of Ultra-Processed Foods
“What we need now are trials that improve our understanding of how ultra-processed foods are linked to chronic diet-related diseases: what physiological processes are affected and what are the precise characteristics of ultra-processed foods which link them to poor health outcomes. Trials are like missing puzzle pieces that we need to fill in to strengthen the evidence base,” says Lane.
Kuhnle believes that a better understanding of the possible underlying mechanisms is needed. “We need to identify which specific food groups are associated with poor health rather than their composition,” he says.
For example, would supermarket bread increase the risk of disease compared to homemade bread, he asks. “We would also like a clearer definition of the term ‘ultra-processed,'” says Kuhnle.
