We’ve shared a variety of posts about the risks of consuming too much processed food, particularly those that are ultra-processed. From higher risk of dementia, heart disease, depression, weight gain, and all cause mortality, the studies share plenty of evidence that ultra-processed foods don’t benefit our health. The latest meta-analysis pooled a great number of studies on the topic and evaluated the evidence surrounding the impact of ultra-processed foods and the impact to our bodies. Their analysis reinforced the findings of many studies and also underscored the need for further research as some data pools were deemed incomplete or inconclusive.
The basics
To start, let’s outline what exactly is considered ultra-processed. There is a wide range of processing:
- Minimally processed foods — such as bagged spinach, cut vegetables and roasted nuts — often are simply pre-prepped for convenience.
- Foods processed at their peak to lock in nutritional quality and freshness include canned tomatoes, frozen fruit and vegetables, and canned tuna.
- Foods with ingredients added for flavor and texture (sweeteners, spices, oils, colors and preservatives) include jarred pasta sauce, salad dressing, yogurt and cake mixes.
- Ready-to-eat foods — such as crackers, granola and deli meat — are more heavily processed.
- The most heavily processed foods (often referred to as ultra-processed) often are pre-made meals including frozen pizza and microwaveable dinners, chips, candy, packaged soups, etc. that go through multiple processes.
The analysis
The review, published in BMJ, provided a comprehensive evaluation of the evidence on adverse health outcomes to date. 45 “pooled meta-analyses” from 14 review articles involving nearly 10 million people were evaluated. There were seven health parameters outlined related to mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes.
To evaluate the credibility of evidence, pre-specified evidence classification criteria were applied:
- convincing (“class I”)
- highly suggestive (“class II”)
- suggestive (“class III”)
- weak (“class IV”)
- or no evidence (“class V”).
The quality of evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) framework, categorized as “high,” “moderate,” “low,” or “very low” quality.
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). Utilizing the classification system, “convincing evidence” (class I) supported the connection between ultra-processed food and higher risk of:
- cardiovascular disease related mortality (+50% risk)
- type 2 diabetes (+12% risk)
- prevalent anxiety outcomes (+48-53% risk)
- combined common mental disorder outcomes (+48-53% risk)
Highly suggestive (class II) evidence indicated that greater exposure to ultra-processed foods was directly associated with higher risks of:
- incident all-cause mortality (+21% risk)
- heart disease related mortality (+40-66% risk)
- type 2 diabetes (+40-66% risk)
- depressive outcomes (+22% risk)
- adverse sleep related outcomes (+40-66% risk)
- obesity (+40-66% risk)
Direct associations were found between high exposure to ultra-processed foods and 32 (71%) health parameters including:
- mortality
- cancer
- mental
- respiratory
- cardiovascular
- gastrointestinal
- metabolic health outcomes
Of the remaining 34 pooled analyses, 21 were graded as suggestive or weak strength (class III-IV) and 13 were graded as no evidence (class V). some uncertainty in the data, which may be partly due to insufficient sample size, particularly in analyses with a small number of original research articles and results showing wide confidence intervals. This underscores the importance of conducting additional original research and subsequent meta-analyses in the respective disease areas.
The image below provides a visual overview of the “Grade” as well as the credibility score of the data from the pooled studies.
The takeaway
At first glance it may seem that a large portion of the health concerns previously tied to ultra-processed foods aren’t backed by strong evidence. This doesn’t, however, mean that there isn’t a tie between the consumption levels of ultra-processed foods and the medical conditions, rather that studies to this point have not adequately established those links. As researchers point out, it is not necessarily an issue of the quality of the study, as much as it is a matter of ethics.
Clare Collins, a nutrition expert at the University of Newcastle in Australia, pointed out that intervention studies or clinical trials — where a potential drug or activity is tried out on people — won’t work in this case because it is not ethical to feed people ultra-processed foods every day “and wait for them to get sick and die.”
The researchers of this latest meta-analysis explain that “Only short-term trials testing the effect of ultra-processed food exposure on intermediate outcomes (such as alterations to body weight, insulin resistance, depressive and anxiety symptoms, gut microbiome, and inflammation) [are] feasible”. In this context, our umbrella review of extant observational epidemiological research provides complementary insights and has implications for public health, especially in light of the current debate about tackling (or not) exposure to ultra-processed foods through public health measures.”
Researchers noted that there is a wide range of processed food consumption throughout the world. Across high income countries, the share of dietary energy derived from ultra-processed foods ranges from 42% (Australia) and 58% (United States), to as low as 10% (Italy) and 25% (South Korea). In low- and middle-income countries such as Colombia and Mexico, for example, these figures range from 16% to 30% of total energy intake.
With our long workdays and hectic lives, it’s easy to grab a prepared meal off the grocery store shelf or stop at a fast-food chain on the way home.
I get that, the idea of cooking and cleaning makes it tempting more times than I’d like to admit. But the more we learn about its dangers to us and our loved ones, the more we have to decide-
Is making a fresh, homemade dinner worth the short-term time investment to ensure long term health?
Instead of a chore, enlist everyone’s help to make it a fun activity. It’s an opportunity to share the day’s events while preparing and eating a wonderful, home cooked meal.
https://www.health.harvard.edu/heart-health/the-sweet-danger-of-sugar
-https://www.health.harvard.edu/staying-healthy/playing-with-the-fire-of-inflammation
-https://www.bmj.com/content/384/bmj-2023-077310
-https://www.washingtonpost.com/health/interactive/2023/american-life-expectancy-dropping/?itid=lk_inline_manual_2
-https://pubmed.ncbi.nlm.nih.gov/34684391/
-https://pubmed.ncbi.nlm.nih.gov/34444936/
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