Diet and food type affect urinary pesticide residue excretion profiles in healthy individuals: results of a randomized controlled dietary intervention trial.

Background: Observational studies have linked pesticide exposure to various diseases, whereas organic food consumption has been associated with positive health outcomes. Organic farming standards prohibit the use of most pesticides, and organic food consumption may therefore reduce pesticide exposure.

Objectives: To determine the effects of diet (Western compared with Mediterranean) and food type (conventional compared with organic) and sex on urinary pesticide residue excretion (UPRE), as well as associations between specific diet components and UPRE.

Methods: In this 2-wk, randomized dietary intervention trial, healthy adults were randomly allocated to an intervention (n = 13) or conventional (n = 14) group. Whereas participants in the intervention group consumed a Mediterranean diet (MedDiet) made entirely from organic foods, the conventional group consumed a MedDiet made entirely from conventional foods. Both groups consumed habitual Western diets made from conventional foods before and after the 2-wk intervention period. The primary outcome was UPRE. In addition, we assessed diet composition and pesticide residue profiles in foods eaten. Participants were aware of group assignment, but the study assessors were not.

Results: During the intervention period, total UPRE was 91% lower with organic (mean 17 μg/d; 95% CI: 15, 19) than with conventional (mean 180 μg/d; 95% CI: 153, 208) food consumption (P < 0.0001). In the conventional group, switching from the habitual Western diet to the MedDiet increased insecticide excretion from 7 to 25 μg/d (P < 0.0001), organophosphate excretion from 5 to 19 μg/d (P < 0.0001), and pyrethroid residue excretion from 2.0 to 4.5 μg/d (P < 0.0001). Small but significant effects of sex were detected for chlormequat, herbicide, and total pesticide residue excretion.

Conclusions: Changing from a habitual Western diet to a MedDiet was associated with increased insecticide, organophosphate, and pyrethroid exposure, whereas organic food consumption reduced exposure to all groups of synthetic chemical pesticides. This may explain the positive health outcomes linked to organic food consumption in observational studies. This trial was registered at www.clinicaltrials.gov as NCT03254537.