Reference: JAMA Intern Med. 2018 Dec 1;178(12):1597-1606
Although COVID-19-related deaths are top of mind, cancer is still a leading cause of death across all ages and backgrounds. Many people have looked to organic foods to limit their exposure to compounds like pesticides and environmental toxins thought to be linked to an increased risk of cancer, assuming that limiting this exposure would decrease the risk of cancer. To date, consumption of organic foods has not been directly linked to a reduced cancer risk. So in a time when many are unemployed and tightening purse strings, does paying more for organic foods provide any measurable benefits?
Investigators in France conducted a web-based prospective cohort study to examine the association between organic food consumption and cancer risk. A total of 68,946 participants (mean age 44 years, 78% female) were enrolled between May 2009 and November 2016. The amount of organic food consumed was quantified as an organic food score. Researchers identified 1,340 cases of cancer during the study period (breast cancer in 34.3%, prostate cancer in 13.4%, skin cancer in 10.1%, colorectal cancer in 7.4%, non-Hodgkin lymphoma in 3.5%, and other lymphoma in 1.1%). Comparing participants in the highest organic food score quartile with those in the lowest, high organic food consumption was associated with decreased overall cancer risk (adjusted hazard ratio 0.75, 95% CI 0.63-0.88), with an absolute risk reduction of 0.6%.
Several caveats limit the generalizability of these findings. First, the study examines baseline diet and organic food consumption patterns and assumes that these remain stable over the follow-up period. It doesn’t stratify the analysis by types of produce and extent of associated pesticide exposure and does not test for pesticide levels in urine samples. Furthermore, it is difficult to control for the “cocktail” effect of these compounds, which may potentiate the risk posed by individual compounds. Additionally, with a mean follow-up of 4 years, the study does not take into account a lifetime of exposures to these chemicals, which is a significant limitation given that cancer can result from cumulative environmental exposures and take decades to develop. On the other hand, the amount of pesticides used in farming that actually wind up ingested may be insufficient to cause significant disease. And don’t discount the compliance effect, where people who are compliant with health recommendations are likely to have better outcomes regardless of the nature of the intervention. Patients who primarily eat organic foods may engage in other healthy behaviors that confound the results (the healthy user effect) and may be more likely to extol the benefits of this for philosophical reasons. Given the potential biases in the methodology of this study, those who want to keep their grocery cart open to non-organic items should do so until better data are available.
For more information, see the topic Adult Preventative Health in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by April Kavanagh, MD, MPH, Faculty Development Fellow and Clinical Instructor of Family Medicine at the University of Virginia. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School, Dan Randall, MD, Deputy Editor for Internal Medicine at DynaMed, and Katharine DeGeorge, MD, MS, Associate Professor of Family Medicine at the University of Virginia and Clinical Editor at DynaMed.