A new study found that glyphosate levels in 16 people (from four families) dropped significantly after one week of switching to an organic diet. The research, co-authored by Friends of the Earth and published in the journal Environmental Research, monitored glyphosate levels in four families from different regions of the U.S. before and after eating an all-organic diet and found that the organic diet intervention reduced glyphosate in the participants’ bodies by an average of 70%. This was the first study to examine the impact of diet on glyphosate exposure. 

Glyphosate, the active ingredient in Roundup, is the most widely used pesticide in the world, and its use has risen dramatically over the last 20 years. Exposure to this chemical occurs directly when people live or work where it is sprayed, and indirectly when contaminated food is consumed.

While the ubiquitous use of glyphosate has led many to hypothesize that human exposure is common, few published studies have evaluated the extent and amount of exposure, and only two previous studies have examined exposure to glyphosate in the U.S. population: one study out of Indiana University that found around 90% of pregnant women tested had detectable levels of glyphosate, and another study out of the University of California, San Diego that found exposure increased from 12% in 1993 to 70% in 2014. However, the new study suggests even more ubiquitous exposure - glyphosate was detected in all study participants and 93.7% of urine samples.

Dietary intervention studies such as this cannot control for the full scope of participants’ exposure to pesticides – people may also be exposed in schools, workplaces or playgrounds. But the significant reduction of detected glyphosate after switching study participants over to an organic diet suggests that their main path of exposure was the consumption of contaminated food. This suggests that for the general American public, dietary exposure is a primary – if not the primary – way they are exposed to glyphosate. Because glyphosate is prohibited for use in organic production, switching to an organic diet reduces exposure.

Additionally, glyphosate levels were consistently higher in children versus parents in this study during both conventional and organic diet phases, (children’s range during conventional diet phase: 1.03 to 6.22 ng/ml versus adult’s range: 0.26 to 0.82 ng/ml). This suggests that children may have more exposure to glyphosate, whether from their environment like playgrounds and parks where the chemical is used to manage weeds, or because they may eat more of the kinds of foods that have high levels of glyphosate like oat cereals, bread, crackers, and granola bars. There is also evidence that children are less efficient at metabolizing some chemicals, which may lead to more accumulation in the body.

Dietary intervention studies are considered the ‘gold standard’ for testing a hypothesis and are used as an assessment tool for establishing causal relationships between food components and outcomes in humans. However, it’s important to note that dietary intervention studies such as this one have important limitations. For example, sample sizes are typically small in intervention studies in comparison with epidemiological observational studies: similar studies have had samples sizes of between 2 and 40, with an average of around 13 people.  Additionally, because this study looked at family groups the replications of each individual are not independent, and family selection was not randomized. Despite these limitations, the strong statistical significance of the drop in glyphosate levels after switching to an organic diet found by this study suggests that the patterns they observed are not likely to occur by chance, and lay the groundwork for future, larger-scale studies on dietary exposure to glyphosate and other pesticides.

The Environmental Research study adds to a growing body of research showing that organic diets can decrease pesticide exposure.  A companion study was published last year showing that an organic diet rapidly and dramatically reduces exposure to other pesticides, including organophosphates, pyrethroids, neonicotinoids and 2,4-D. Previous studies have mirrored these results, showing that organic diets significantly lower dietary exposure to organophosphorus pesticides in children and adults.

This is the first study of its kind to show that organic diets can reduce indirect exposure to glyphosate, and also suggests that more research needs to be done to measure exposure from diets and from the environment.