The new study is the first to investigate what the effect of eating foods high in pesticide residue might be on semen quality.
Previous studies have reported a link between occupational and environmental exposure to pesticides and lower semen quality.
However, data on associations between pesticide residues in food and adverse health effects have been limited, and no previous studies have looked at what the effect on semen quality might be.
"To our knowledge, this is the first report to link consumption of pesticide residues in fruits and vegetables, a primary exposure route for most people, to an adverse reproductive health outcome in humans," says Jorge Chavarro, assistant professor of nutrition and epidemiology and the senior author of the new study.
The EARTH study
Chavarro and colleagues analyzed data from 155 men who were part of the National Institute of Environmental Health Sciences-funded Environment and Reproductive Health (EARTH) study.
As well as validated survey information on the participants' diets, a total of 338 semen samples were assessed as part of the study.
Using data from the U.S. Department of Agriculture Pesticide Data Program, the researchers categorized the following as fruits and vegetables that contained high amounts of pesticide residues: peppers, spinach, strawberries, apples and pears.
Fruits and vegetables that were considered to have low or moderate amounts of residue included: peas, beans, grapefruit and onions.
The authors found that men who ate more than 1.5 servings per day of the fruits and vegetables considered to be high in pesticide residue had 49% lower sperm count and 32% lower percentage of normal sperm than men who ate less than 0.5 servings of these foods each day.
Interestingly, men who ate the most amounts of fruits and vegetables with low-to-moderate amounts of pesticide residue had a higher percentage of normal sperm, compared with those who ate less fruits and vegetables with the same levels of residue.
As such, Chavarro says the findings of the study should not discourage men from eating fruits and vegetables:
"In fact, we found that consuming more fruits and vegetables with low pesticide residues was beneficial. This suggests that implementing strategies specifically targeted at avoiding pesticide residues, such as consuming organically grown produce or avoiding produce known to have large amounts of residues, may be the way to go."
The researchers took into account other factors known to affect sperm quality, such as body mass index (BMI) and whether or not the participants smoked. However, in their conclusion, they write "our results must be interpreted with caution," because diet was assessed only once in the study, and so true intake may have been misclassified.
Also, the researchers did not have data available to them on whether the foods eaten by the men were organically or conventionally grown. And because pesticide exposure was estimated based on what foods the participants had eaten rather than individual measurements, there may have been some misclassification of exposure levels.