Dog food chemicals could explain an alarming drop in the sperm counts of male dogs over the past three decades, according to a new study. The findings suggest environmental chemicals may also be linked to human male infertility.
In the study, which was published in the journal Scientific Reports on Tuesday, researchers at the University of Nottingham were able to show a potential link between chemicals found in popular dog food brands and a dramatic decline in the sperm quality of U.K. stud dogs over the past 26 years.
In a press release, lead researcher Richard G. Lea said the findings are unprecedented and could indicate human fertility is also being impacted by environmental chemicals.
“This is the first time that such a decline in male fertility has been reported in the dog, and we believe this is due to environmental contaminants, some of which we have detected in dog food and in the sperm and testes of the animals themselves. While further research is needed to conclusively demonstrate a link, the dog may indeed be a sentinel for humans — it shares the same environment, exhibits the same range of diseases, many with the same frequency, and responds in a similar way to therapies.”
The UN research team collected a total of 1,925 semen samples from stud male border collies, curly coat retrievers, Labrador retrievers, German shepherds, and golden retrievers over the course of 26 years. Between 42 and 97 dogs were analyzed each year, and their sperm counts steadily declined. Between 1989 and 1998, sperm counts dropped by 2.5 percent every year, and the counts dipped by 1.2 percent a year between 2002 and 2014. Overall, the sperm counts dropped around 35 percent over the course of the study. The studs, which were used to breed service dogs, were from a highly controlled population, and genetics were ruled out as a possible cause of the problem.
Dog food chemicals appeared to not only lower sperm counts in dogs, but they may have caused other fertility issues. The study showed male puppies fathered by dogs with lesser quality semen were more likely to have cryptorchidism, a condition where the testes do not descend into the scrotum.
Among the chemicals found in the dogs’ sperm were diethylhexyl phthalate (DEHP) and polychlorinated bisphenol 153 (PCB153), which are environmental contaminants known to cause fertility problems in other species.
The study also found PCBs and phthalates in many wet and dry varieties of popular commercial dog food brands. These chemicals are used in the production of plastics and furniture flame retardants and can leach into food through packaging materials. They also seep into the food chain because plants and livestock absorb them from the environment.
According to the Telegraph, recent studies have shown that only a quarter of young men are able to produce quality sperm counts, and the average semen volume has plummeted by around 25 percent since the 1940s. Scientists have been unable to pinpoint the cause, but the UN study may shed some light on the issue.
Fertility experts believe more research needs to be done to establish a firm link between environmental chemicals and male infertility, but they believe the research on dog food chemicals is eye-opening.
“The association with environment chemicals, while not causal at this stage, is certainly one to put on the watch list,” said Darren Griffin, professor of genetics at the University of Kent.
Meanwhile, Allan Pacey, spokesperson for the British Fertility Society, said the study could serve as a warning for humans.
“Although there is conflicting evidence to suggest that sperm quality in humans has declined significantly, this study is particularly interesting as the results suggest an increase in the problems of the dog’s testicles and a decline in the number of female dogs born over the period.”
“In addition, concentrations of some environmental chemicals in the dog’s testicles as well as in commercial dog foods were also detected. Indeed, because dogs share the human home, this could suggest that they might be a useful model species to detect possible threats to male reproductive health.”
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