A new massive umbrella review of epidemiological meta-analyses reinforces the idea that ultra-processed food is bad for most aspects of human health [1].
Is it even food?
Many words have been uttered about the dangers of ultra-processed food, so can another study add anything new? The authors of this new paper published in the prestigious journal BMJ note that “no comprehensive umbrella review has offered a broad overview and assessment of the existing meta-analytic evidence” on the health effects of ultra-processed food – a gap they attempted to bridge by digging into 45 existing meta-analyses with a total coverage of almost 10 million participants.
As the attached editorial clarifies, ultra-processed foods are not just modified foods, but, according to the established NOVA model, “formulations of often chemically manipulated cheap ingredients such as modified starches, sugars, oils, fats, and protein isolates, with little if any whole food added, made palatable and attractive by using combinations of flavors, colors, emulsifiers, thickeners, and other additives.”
Basically, heavy processing completely rearranges food, creating a product that does not exist in nature and is not compatible with a gastrointestinal system molded by millions of years of evolution. Ultra-processed foods are often stripped of important nutrients such as flavanols and pumped with fat, salt, and sugar to make them irresistible to us.
71% of outcomes affected
The study has yielded some expected and some surprising results. It found that higher intake of ultra-processed foods increases the chances of all-cause mortality by as much as 21% and cardiovascular disease-related mortality by 50%.
It has been shown, including by clinical trials [2], that consuming ultra-processed foods increases the risk of obesity and adverse metabolic outcomes. This was confirmed by this study: gorging on ultra-processed foods increased the chances of obesity by 55%, metabolic syndrome by 25%, and Type 2 diabetes by 40%. Even a slight 10% increase in ultra-processed food consumption was associated with deleterious health effects, such as a 12% increase in chances of diabetes. In total, direct associations were found with 71% of the analyzed health outcomes.
One of the strongest associations observed was with various aspects of mental health, such as sleep quality, anxiety, and common mental disorders. However, this might be due to reverse causation, as depression and other mental illnesses can cause people to consume large quantities of unhealthy foods.
On the other hand, the study showed only limited association between ultra-processed foods and such outcomes as asthma, non-alcoholic fatty liver disease, and hypertension.
No evidence for cancer risk
Another surprise was little to no association between ultra-processed foods and cancer mortality or incidence. This is intriguing, since numerous earlier studies have shown this link [3]. Evidence regarding specifically ultra-processed meat is considered so strong that it became one of the very few food categories to be designated as a known carcinogen by the World Health Organization. Obesity is a major risk factor for cancer [4], so ultra-processed foods should affect cancer outcomes at least via obesity.
This does not mean that the link between ultra-processed food and cancer does not exist. One possible explanation is that in this study, no distinction was made between the types of ultra-processed food, which might have blunted the effect of some of these types (such as processed meat).
Populational studies can be highly heterogeneous and hard to interpret, and they can only show correlation and not causation. Even if there is no cancer connection, there are still plenty of reasons to avoid ultra-processed foods altogether. Read our 2022 interview with Prof. Albert-László Barabási for his exciting take on ultra-processed foods.
Our umbrella review provides a comprehensive overview and evaluation of the evidence for associations between dietary exposure to ultra-processed foods and various adverse health outcomes. Our review included 45 distinct pooled analyses, encompassing a total population of 9,888,373 participants and spanning seven health parameters related to mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes. Across the pooled analyses, greater exposure to ultra-processed foods, whether measured as higher versus lower consumption, additional servings per day, or a 10% increment, was consistently associated with a higher risk of adverse health outcomes (71% of outcomes).
Literature
[1] Lane MM, Gamage E, Du S, et al. (2024) Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses. BMJ; 384:e077210.
[2] Hall, K. D., Ayuketah, A., Brychta, R., Cai, H., Cassimatis, T., Chen, K. Y., … & Zhou, M. (2019). Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake. Cell metabolism, 30(1), 67-77.
[3] Wang, L., Du, M., Wang, K., Khandpur, N., Rossato, S. L., Drouin-Chartier, J. P., … & Zhang, F. F. (2022). Association of ultra-processed food consumption with colorectal cancer risk among men and women: results from three prospective US cohort studies. bmj, 378.
[4] Pati, S., Irfan, W., Jameel, A., Ahmed, S., & Shahid, R. K. (2023). Obesity and cancer: A current overview of epidemiology, pathogenesis, outcomes, and management. Cancers, 15(2), 485.
