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updated 3/30/2015 7:46:49 PM ET 2015-03-30T23:46:49

For men who are having fertility problems, eating lots of pesticide-laden fruits and vegetables may be bad news, a new study suggests.

Among the men in the study, who were all attending a fertility clinic, those who ate lots of fruits and vegetables known to contain high levels of pesticides had about half as many sperm, and almost a third fewer normal sperm, than men who consumed less of the toxin-laden produce.

If confirmed in a wider population, the findings could have important implications for male reproductive health, the researchers said in their study, published today (March 30) in the journal Human Reproduction. [ Top 10 Good Foods Gone Bad ]

"These results do not mean you should stop consuming fruits and vegetables," said Dr. Jorge Chavarro, the senior author of the new study and a professor of nutrition and epidemiology at Harvard University's School of Public Health. Rather, the study suggests that men seeking a healthy sperm count should eat fruit and vegetables that are organically grown, or known to be low in pesticide residues, Chavarro said.

The researchers said that peas, beans, grapefruit and onions are considered low in pesticide residues, whereas peppers, spinach, strawberries, apples and pears tend to have more pesticides.

The effects of pesticides on men's semen have been widely studied. For instance, research has linked pesticides to sterility in men who work in agriculture or as exterminators. But this is the first study to look at how pesticides in a man's diet affect sperm count and sperm quality, the researchers said.

Pesticides and fertility

In the study, Chavarro and his colleagues analyzed 338 semen samples from 155 men seeking fertility treatment at a clinic in Boston from 2007 through 2012. The men were between ages 18 and 55.

The researchers surveyed the men about their diets, including how often they ate different types of fruits and vegetables. Scientists divided the foods into groups of high, moderate or low pesticide residues, based on annual pesticide data from the United States Department of Agriculture. [ Pesticides Lurk in Fruits & Veggies (Infographic) ]

Experts look at three factors when assessing male fertility: sperm count (number of cells), sperm morphology (shape) and sperm motility (swimming ability).

The results showed that the men who ate the most pesticide-laden fruit and vegetables had an average sperm count of 86 billion sperm per ejaculate, compared with the 171 million sperm produced by the men with the lowest pesticide intake.

"The difference in total sperm count between the highest and lower intakes was almost 50 percent," Chavarro told Live Science. "That's a big, big difference."

Not only that, but pesticide intake also affected the number of sperm cells that formed properly. Among men who consumed more pesticide-rich produce, 5.7 percent of sperm were normal, compared with 7.8 percent of sperm among men who got less pesticide content from their fruits and veggies.

The total amount of fruits and vegetables the men ate had no effect on their sperm, the researchers found.

Word of caution

But the findings come with a number of caveats. The study involved men who were already seeking a diagnosis for fertility problems, so the results may not apply to the wider public. "In this population, almost half of [the men] had at least one or more" irregularities with their sperm, Chavarro said.

"These findings need to be replicated in various populations," wrote Dr. Hagai Levine of the Hebrew University of Jerusalem in Israel and Dr. Shanna Swan of Mount Sinai Hospital in New York, in an editorial accompanying the study. The effects of the pesticides in a man's diet on his semen could depend on genetic or developmental factors, the editorial writers added.

In addition, the researchers in the new study didn't actually measure the level of pesticides the men consumed.

Chavarro said he hopes his study will lead to further research on how pesticide exposure affects sperm, "but I don’t think it can be the last word," he said.

© 2012 LiveScience.com. All rights reserved.

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