Women undergoing infertility treatment who consumed more high-pesticide residue foods had a lower likelihood of clinical pregnancy and live birth compared with their peers, a new prospective epidemiological study showed.
Compared with women in the lowest quartile of high-pesticide residue fruits and vegetable intake (<1.0 servings/day), women in the highest quartile (≥2.3 servings/day) had an 18% lower probability of achieving a clinical pregnancy (95% confidence interval [CI], 5% – 30%) and a 26% lower probability of having a live birth (95% CI, 13% – 37%).
Moreover, substituting just one serving/day of low-pesticide residue produce for one serving/day of high-pesticide residue produce was associated with 79% higher odds of clinical pregnancy (95% CI, 11% -188%) and 88% higher odds of live birth (95% CI, 16% – 205%).
“These data suggest that dietary pesticide exposure within the range of typical human exposure may be associated with adverse reproductive consequences,” write Yu-Han Chiu, MD, ScD, from the Department of Nutrition and the Department of Epidemiology at Harvard T.H. Chan School of Public Health in Boston, Massachusetts, and colleagues.
The researchers published their results online today in JAMA Internal Medicine.
Dr Chiu and colleagues studied 325 participants with a mean age of 35.1 years in the Environment and Reproductive Health cohort, established in 2006 to identify determinants of fertility in patients treated at the Massachusetts General Hospital Fertility Center. The women underwent assisted reproduction during 2007 to 2016.
Using averaged surveillance data from 2006 to 2015 from the US Department of Agriculture’s Pesticide Data Program, which reports annually on pesticide residue status in the US food supply, the investigators established typical pesticide residue burden scores for 36 commonly consumed fruits and vegetables based on three Pesticide Data Program measures.
These contamination scores ranged, for example, from a low of 0 for peas, onions, corn, and orange juice to a high of 6 for raw spinach, strawberries, and sweet peppers, with bananas and yams coming in at 3. Items with a burden of 4 or more were considered high-pesticide-residue foods, whereas those with a burden of less than 4 were deemed low-pesticide-residue foods. Overall, 22 were classified as low-contamination and 14 as high-contamination foods.
Women self-reported consumption of these and other dietary items via a validated take-home questionnaire in which they reported the frequency and amounts of foods, beverages, and supplements consumed during the past year.
The researchers then estimated associations between infertility treatment outcomes and high- vs low-pesticide-residue exposure. Interestingly, no associations emerged between pesticide residue exposure and markers of response to ovarian stimulation, fertilization rate, or embryo quality.
“This is the first study to look at this specific question, so additional work is certainly required before we can definitely say that pesticide contamination in fruits and vegetables is harmful to reproduction,” senior author Jorge E. Chavarro, MD, ScD, also from the Harvard T.H. Chan School of Public Health, told Medscape Medical News. Although it likely does not hurt to avoid high-pesticide-residue foods, Dr Chavarro continued, “What we cannot say with certainty at this moment is whether this change in exposure will lead to changes in fertility or other health outcomes. It will definitely be important to address this question in other studies, including those of couples attempting conception naturally,” he said.
The authors note, however, that in previous research, occupational and residential exposure to pesticides has been linked to deleterious effects on reproductive health, including stillbirth, diminished fertility, spontaneous abortion, and developmental abnormalities. They also refer to a large Norwegian study that suggested that pregnant women who ate organic vegetables had a lower risk for preeclampsia.
They explain that miscarriage and preeclampsia may be related through oxidative stress–induced placental dysfunction in which pesticide exposure may play a role. “Pesticide-induced placental dysfunction may explain the relationship of lower rates of clinical pregnancy loss associated with lower intake of high-pesticides [fruits and vegetables] in the present study, as well as lower prevalence of preeclampsia associated with organic vegetable consumption in the earlier study,” the authors write.
In an invited commentary, pediatrician Phillip J, Landrigan, MD, from the Arnhold Institute for Global Health, Icahn School of Medicine at Mount Sinai, New York City, who was not involved in the study, interpreted the Harvard study in the context of mounting evidence of declining human fertility and increasing reproductive impairment in the West, including rapidly falling sperm counts.
Pointing to the likely role of endocrine-disrupting environmental exposures in this trend, Dr Landrigan urges physicians to alert patients to the hidden risks of pesticides. “Encourage our patients to eat organic. And educate elected officials and other policy makers about the hazards of pesticides,” he writes.
Although the current observational study cannot establish a direct causal link between pesticides and reproductive impairment, its observations “send a warning that our current laissez-faire attitude toward the regulation of pesticides is failing us,” he continues. “We can no longer afford to assume that new pesticides are harmless until they are definitively proven to cause injury to human health.”
He calls for recognition of the hidden costs of deregulation and the application of the same rigorous premarket assessment and postmarket surveillance to new pesticides as are applied to drugs.
The study was supported by the National Institute of Environmental Health Sciences and the National Institute of Diabetes and Digestive and Kidney Diseases. The authors and the editorial commentator have disclosed no relevant financial relationships.
JAMA Intern Med. Published online October 30, 2017. Article full text, Commentary full text
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