Worldwide, the number of new cases of cancer was estimated in 2012 at more than 14 million,1,2 and cancer remains one of the leading causes of mortality in France. Among the environmental risk factors for cancer, there are concerns about exposure to different classes of pesticides, notably through occupational exposure.3 A recent review4 concluded that the role of pesticides for the risk of cancer could not be doubted given the growing body of evidence linking cancer development to pesticide exposure. While dose responses of such molecules or possible cocktail effects are not well known, an increase in toxic effects has been suggested even at low concentrations of pesticide mixtures.5
Meanwhile, the organic food market continues to grow rapidly in European countries,6 propelled by environmental and health concerns.7-10 Organic food standards do not allow the use of synthetic fertilizers, pesticides, and genetically modified organisms and restrict the use of veterinary medications.11 As a result, organic products are less likely to contain pesticide residues than conventional foods.12,13 According to a 2018 European Food Safety Authority13 report, 44% of conventionally produced food samples contained 1 or more quantifiable residues, while 6.5% of organic samples contained measurable pesticide residues. In line with this report, diets mainly consisting of organic foods were linked to lower urinary pesticide levels compared with “conventional diets” in an observational study14 of adults carried out in the United States (the median dialkyphosphate concentration among low organic food consumers was 163 nmol/g of creatinine, while among regular organic food consumers it was reduced to 106 nmol/g of creatinine). This finding was more marked in a clinical study15 from Australia and New Zealand (a 90% reduction in total dialkyphosphate urinary biomarkers was observed after an organic diet intervention) conducted in adults.
Because of their lower exposure to pesticide residues, it can be hypothesized that high organic food consumers may have a lower risk of developing cancer. Furthermore, natural pesticides allowed in organic farming in the European Union16 exhibit much lower toxic effects than the synthetic pesticides used in conventional farming.17 Nevertheless, only 1 study18 to date has focused on the association between frequency of organic food consumption and cancer risk, reporting a lower risk of non-Hodgkin lymphoma (NHL) only. However, consumption of organic food was assessed using only a basic question. Multiple studies19-24 have reported a strong positive association between regular organic food consumption and healthy dietary habits and other lifestyles. Hence, these factors should be carefully accounted for in etiological studies in this research field. In the present population-based cohort study among French adult volunteers, we sought to prospectively examine the association between consumption frequency of organic foods, assessed through a score evaluating the consumption frequency of organic food categories, and cancer risk in the ongoing, large-scale French NutriNet-Santé cohort. The follow-up dates of the study were May 10, 2009, to November 30, 2016.