Trending Topics pieces (Article Analyses, Evidence Clips and Other Topics) are published in timely response to recent media and journal articles, position statements, clinical guidelines, etc. Since they are based on the most recent evidence/publications, they may not be consistent with PEN evidence in other PEN content areas. As soon as possible, when this occurs, the PEN content will be reviewed and updated as needed.
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Ultra-processed Foods and Early Death
Researchers continue to explore the relationship between the foods we eat and health outcomes. The British Medical Journal (BMJ) recently published two articles on the health effects associated with the consumption of ultra-processed foods and early death:
The National Health Service (NHS) in the U.K. has provided this analysis of the research, which notes the challenges of cohort studies, including the inability to prove cause and effect, the importance of potential confounding factors with observational research, and the difficulty of defining ultra-processed foods. People who frequently eat ulta-processed foods are different in several ways including income, physical activity and smoking habits, from people who eat foods prepared from scratch (1); it is not possible in studies such as these to fully control for these differences. Thus, it is cannot be assumed that the ultra-processed foods actually caused the cardiovascular disease or early deaths or that other aspects of their lifestyle were more important.
In addition, see the February 2019 PEN Trending Topic: The Association Between Ultraprocessed Food Consumption and the Risk of Mortality – What is the Real Deal?
References:
- Schnabel L, Kesse-Guyot E, Allès B, Touvier M, Srour B, Hercberg S, et al. Association between ultraprocessed food consumption and risk of mortality among middle-aged adults in France. JAMA Intern Med. 2019 Feb 11. doi:10.1001/jamainternmed.2018.7289. [Epub ahead of print]. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/30742202
Posted: 2019-06-06
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The Association Between Ultraprocessed Food Consumption and the Risk of Mortality – What is the Real Deal?
Originally Posted February 15, 2019. Reposted June 5, 2019
Another observational nutrition study is making headlines around the world (1-3) but is also raising concerns about the failure of news stories to address the
significant limitations of the study. The observational prospective cohort study looked at the association between ultraprocessed food consumption and the risk of mortality in middle-aged adults in France (4). The authors concluded that an association existed based on the data of more than 44,000 participants.
A PEN Evidence Analyst offered this analysis:
The results portray a very weak relationship between ultraprocessed foods and mortality. The effect size, which was equal to a hazard ratio of 1.14, is so small that it is not likely of importance. GRADE guidelines encourage that for an observational study an effect size should be greater than 2, or better yet 5, before we should assume that there is an important effect (5). This hazard ratio of 1.14 was statistically significant, which is not surprising because there were over 44,000 participants in the study. When the sample size is very large, statistical significance is highly likely even when the effect is so small that it is not likely of any real importance.
Additional concerns are that the categorization of foods in the ultraprocessed category included sugar-sweetened beverages and highly processed snack foods but also included ready-made meals and breads, which could be quite nutritious. Further, the researchers allowed the participants to select which 24-hour periods they reported their food intake, so we don’t know how well their selections reflect typical intakes.
The results observed could be due to the fact that those that ate the most of these ultraprocessed foods were those most likely to have higher mortality rates for reasons beyond dietary intake. The individuals consuming the most of these ultraprocessed foods were more likely to be of lower income, smoke and/or be single obese males with low levels of physical activity. Some additional variable or variables related to these variables that were controlled for in the analysis could be the actual causal factor for mortality. Therefore, residual confounding may explain this study’s results.
The researchers did mention that reverse causation was possible; that is those people who are at higher risk of death from a chronic disease may have been selecting more processed foods. This type of study design cannot rule out reverse causation.
The NHS and Science Media Centre reviews also outline the limitations and put the study and its findings into perspective.
References:
- Scutti S. Eating 'ultraprocessed' foods accelerates your risk of early death, study says. CNN. 2019 Feb 12. Available from: https://edition.cnn.com/2019/02/11/health/ultraprocessed-foods-early-death-study/index.html
- Eating ultra-processed foods can increase risk of early death: study. CTV. 2019 Feb 12. Available from: https://www.ctvnews.ca/health/eating-ultra-processed-foods-can-increase-risk-of-early-death-study-1.4293071
- Donnelly L. Modern diets could be killing us, suggests major study on ultra-processed foods. The Telegraph News. 2019 Feb 11. Available from: https://www.telegraph.co.uk/news/2019/02/11/modern-diets-could-killing-us-suggests-major-study-ultra-processed/
- Schnabel L, Kesse-Guyot E, Allès B, Touvier M, Srour B, Hercberg S, et al. Association between ultraprocessed food consumption and risk of mortality among middle-aged adults in France. JAMA Intern Med. 2019 Feb 11. doi:10.1001/jamainternmed.2018.7289. [Epub ahead of print]. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/30742202
- Guyatt GH, Oxman AD, Sultan S, Glasziou P, Akl EA, Alonso-Coello P, et al. GRADE guidelines: 9. Rating up the quality of evidence. J Clin Epidemiol. 2011 Dec;64(12):1311-6. doi: 10.1016/j.jclinepi.2011.06.004. Epub 2011 Jul 30. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/?term=21802902
Posted: 2019-06-05