Sperm and Pesticides
half a teaspoon – this is how much a man typically ejaculates each time.
But as we all know it takes only one sperm cell to fertilize a woman’s egg – and there is stiff competition for that honor. In fact, the average ejaculate contains 200 million sperm.
To fertilize an egg the old-fashioned way, sperm need to be able to swim. However, this is not so with in-vitro (IVF or test tube) fertilization.
In fact, when IVF technicians use tiny, robot-controlled glass straws to insert a single sperm inside an egg, they sometimes beat the sperm with the glass until it stops moving. The only thing that matters is the DNA inside the sperm.
Most people use the terms sperm and semen interchangeably. But sperm cells are only one component of ‘semen’. Semen also contains substances from the prostate and a pair of rabbit ear-shaped organs inside the pelvis called the seminal vesicles.
Sperm cells, which are made in the testicles, need lots of high-octane fuel to whip their tails. Lucky for them (and us), sperm get the fuel they need in the form of sugar fructose, which is supplied by the seminal vesicles. Fluid from the prostate contains chemicals that cause semen to liquefy once it’s inside the female. Without it, sperm would be locked in place and unable to swim.
A study, carried out a fertility centre in Boston, Massachusetts, although small in scale, with only 155 men enrolled, experts said it should not alarm men into cutting back on their fruit and veg consumption. However, it is the first to suggest that pesticides, some of which are known to affect the action of certain hormones, including the male sex hormone testosterone, could be affecting fertility through the traces found in the food we eat, and scientific commentators said it merited further research.
The researchers studied sperm samples from the men who were attending a fertility clinic because they and their partners were having trouble conceiving.
The men also answered 131 questions about the food they ate, including how often and in what quantities they ate 38 fruits and vegetables like apples, avocados or cantaloupe. The researchers compared their answers to annual U.S. Department of Agriculture data on average pesticide residue in types of produce.
For example, peppers, spinach, strawberries, apples, and pears tend to have high levels of pesticide residue, whereas peas, beans, grapefruit, and onions have low-to-moderate amounts.
Half the men ate at least 3.5 servings of fruits and vegetables per day.
The total amount of fruits and veggies in the diet was not associated with semen quality. But men who ate at least 1.5 servings of high-pesticide produce per day had about half as many sperm in their semen, and two-thirds as many normal-appearing sperm, as men who ate less than half a serving of high-pesticide produce per day, according to results in Human Reproduction.
“This does not necessarily imply reduced fertility,” said senior author Jorge Chavarro of Harvard T.H. Chan School of Public Health. “We will continue our work to try to figure out to what extent these effects in semen quality may ultimately impact fertility.”
Pesticide-laden produce was linked to poorer semen quality even when the authors accounted for smoking status and the men’s weight in relation to their height, which can both affect sperm quality. In fact, men who ate more high-pesticide fruits and vegetables tended to exercise more and have a healthier diet overall, Chavarro said.
Other studies had tied poorer semen quality to occupational and environmental exposure to pesticide chemicals, and the latest results indicate the same is true for pesticides in the diet.
Given that pesticides are designed to kill and harm pest reproduction, it is not surprising that they are harmful to human reproduction, said Dr. Hagai Levine of the Icahn School of Medicine at Mount Sinai in New York and the Hebrew University-Hadassah in Jerusalem , who co-authored an editorial published with the findings.
Recent evidence indicates that sperm quality is an important measure of general health, and poor semen quality predicts higher risk of death, Levine told Reuters Health by email.
The researchers did account for other factors like age, body mass, physical activity, race, smoking, urogenital conditions, season and year, he noted.
While these results do not point to any one specific pesticide or group of pesticides – they do suggest that pesticide mixtures, as used in agriculture, may be to blame.
“Gaining a better understanding on which specific mixtures or pesticides explain this relation will be key moving forward, however,” he said.
He and his team are actively investigating whether women’s markers of fertility may also be linked to pesticides in the diet, he said.
Organic produce carries less pesticide residue, if you can afford it, he said. Another option is to choose fruits and vegetables known to have low levels of pesticide residues, he said.
Some pesticides remain on the surface of products and may come off when washed, but many others are absorbed into the fruit, and washing will do nothing in those cases.
Previous studies have shown that eating non-organic fruit and vegetables can lead to measurable levels of pesticides in urine. Research has also suggested a link between working closely with pesticides and lower sperm counts.
The findings were based on 338 semen samples, along with information about the men’s diet collected via questionnaire. Information about which products were likely to have higher levels of pesticides was based on US Department of Agriculture advice. At no point were the actual pesticide levels on the fruits and vegetables consumed by the men measured.
These findings should not discourage the consumption of fruit and vegetables in general – in fact, it was 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.