Diets rich in fruits and vegetables are now widely accepted as ideal toward the optimization of human health. But pesticide residue on such foods pose several health risks, including significantly lowered sperm counts. Put another way, men who consume produce with a certain amount of chemical residues can be significantly less fertile than those who avoid such foods.

Certain fruits and vegetables carry higher quantities of pesticides. It is these that are responsible for sperm quantities up to 50 percent below the levels recorded in those who eat just the smallest amount of these same foods.

The latest findings come from a study published in Human Reproduction. One of the authors, epidemiologist Jorge Chavarro, also said that men who consumed the most of the high-pesticides fruits also had abnormally shaped sperm, as much as 32 percent more.

According to the nonprofit Environemental Working Group, fruits and vegetables that carry the highest amounts of pesticide residue include spinach, celery, strawberries and apples. Those with the lowest residue levels include corn, avocados and pineapples.

Using data from 155 men involved with a study in Boston named Environment and Reproductive Health (EARTH),  Chavarro says the difference in sperm count between the groups was “quite large.” EARTH is funded by the National Institute of Environmental Health Sciences, a part of the U.S. National Institutes of Health.

Although the sample of men studied is relatively small, Chavarro nevertheless said that men already concerned about low fertility could do worse than avoiding high-pesticide fruits and vegetables. He suggests a “better safe than sorry approach.” The latest study reiterates previous research showing farmworkers exposed to pesticides at high levels do indeed have lower sperm counts.

Scientists do not understand how male fertility is impaired by pesticides, only that it is. A popular theory, however, is that many pesticides function by disrupting endocrine systems, interfering with hormonal systems. Hormones are integral to possibly thousands of cellular processes and these, ultimately, lead to sperm production. Also, some studies have shown a number of pesticides can cause increased apoptosis – also known as programmed cell death – in animal gonads of various animals.