Canine Infertility — Is Food to Blame?

Analysis by Dr. Karen Shaw Becker

canine infertility

Story at-a-glance -

  • The 2016 results of a 26-year study suggest the quality of sperm in intact male dogs in the U.K. has decreased dramatically
  • The research team found hormone-disrupting chemicals in the dogs’ testes and sperm at levels high enough to have a harmful effect on sperm function
  • In a just-published follow-up study, the researchers found an identical effect from the same chemicals in the sperm of both men and male dogs
  • These study results are a clear indication that man-made substances are disrupting the natural chemical messenger system that controls hormones in both men and male dogs
  • The natural follow-up to these studies is to look at how the same chemicals affect females

In 2016, a team of U.K. researchers at the University of Nottingham School of Veterinary Medicine and Science revealed that the fertility of dogs had decreased precipitously over the preceding 35 years. Their study findings, published in the journal Scientific Reports, showed that the quality of sperm in a population of intact adult male dogs has fallen significantly over a 26-year period.1

The researchers discovered hormone-disrupting chemicals in the dogs’ testes and sperm — the same chemicals also found in some commercial dog foods — in concentrations high enough to have a harmful effect on sperm function. The scientists suspected the presence of these chemicals may play a role in the reported significant decline in the quality of human sperm as well. According to lead researcher Richard Lea, Ph.D.,:

"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."2

Now a second study conducted by the same team of experts and published in March, suggests that indeed, environmental contaminants found in the home and diet have the same adverse effects on the fertility of both men and male dogs.3

Study Looked at Two Common Environmental Contaminants

In the most recent study, the researchers set out to test the effects of two man-made chemicals. The first was DEHP, a substance that makes plastics flexible and is used in a variety of consumer products including carpets, flooring, upholstery, clothes, wires and toys.

The second was the industrial chemical polychlorinated biphenyl (PCB 153), used in plasticizers, surface coatings and paints. PCB 153 has been banned globally but still exists in the environment, including in food. Both chemicals have been found in commercially available dog food.

The research team performed identical experiments using the sperm of donor men (nine samples) and intact male dogs (11 samples) living in the same region of the U.K. To mimic the amount of chemicals that would be naturally encountered in a home environment, the scientists incubated the samples in a lab together with the DEHP and PCB153 at concentrations previously detected in the sperm of pet dogs undergoing routine reproductive assessments.

Results Confirmed Damaging Effects of Exposure on Both Human and Canine Sperm

The research findings showed that both chemicals were present at levels typical of environmental exposure and had the same damaging effects on both human and canine sperm. According to Lea:

"This new study supports our theory that the domestic dog is indeed a 'sentinel' or mirror for human male reproductive decline and our findings suggest that human-made chemicals that have been widely used in the home and working environment may be responsible for the fall in sperm quality reported in both man and dog that share the same environment.

Our previous study in dogs showed that the chemical pollutants found in the sperm of adult dogs, and in some pet foods, had a detrimental effect on sperm function at the concentrations previously found in the male reproductive tract. This new study is the first to test the effect of two known environmental contaminants, DEHP and PCB153, on both dog and human sperm in vitro [in a lab], in the same concentrations as found in vivo [in a living organism]."4

In both the dogs and the men, the effect of exposure to the two environmental contaminants was reduced sperm motility and increased fragmentation of DNA (the separation or breaking of DNA strands into pieces). According to study co-author Rebecca Sumner, Ph.D.:

"We know that when human sperm motility is poor, DNA fragmentation is increased and that human male infertility is linked to increased levels of DNA damage in sperm. We now believe this is the same in pet dogs because they live in the same domestic environment and are exposed to the same household contaminants.”5

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What Effect Are These Chemicals Having on Female Fertility?

According to lead researcher Lea, the natural follow-up to these studies is to look at how the same chemicals affect females, as well as how where we live affects chemicals in sperm and sperm quality. These particular pollutants, DEHP and PCB 153, are used primarily in Western industries, and since other studies indicate sperm decline isn’t occurring in Asia, Africa or South America, this could be a predominantly Western problem.6

While other factors such as air pollution and obesity may also play a role in sperm decline, the fact that the sperm of dogs and humans are impacted in the same way by DEHP and PCB 163 adds weight to the idea that manmade substances are disrupting the natural chemical messenger system that controls hormones.

Dogs’ Sperm Motility Declined by 35% Over 26 Years

The dogs involved over the 26-year study (1988 to 2014) I mentioned earlier were intact male assistance dogs. Five breeds were represented, including the Labrador retriever, golden retriever, Curly-Coated retriever, Border Collie and German Shepherd. From 42 to 97 dogs were studied each year.

All semen samples were processed and analyzed by the same laboratory, using the same protocols. The sperm was assessed for normal forward movement patterns and normal appearance under a microscope. Over the 26-year study, the researchers noted a conspicuous decrease in the number of normal sperm, with sperm motility falling by around 35% overall.

During a 10-year period from 1988 to 1998, sperm motility declined by 2.5% per year. From 2002 to 2014, and after dogs with decreased fertility were retired from the study, the decline was measured at a rate of 1.2% per year. The slowing decline in the final years of the study could also be a result of stricter regulations on the use of certain hormone disrupting chemicals.

Another irregularity the researchers discovered was that male offspring of dogs with decreased sperm quality showed a greater tendency toward cryptorchidism, a condition in which the testicles don’t descend normally into the scrotum. In addition, they noted a decline in the number of male puppies born versus females.

Chemicals Found in Dogs’ Sperm Also Found in Commercial Dog Foods

The sperm collected from the dogs in the study, as well as the testes of neutered study dogs, were found to contain environmental contaminants at levels high enough to interfere with sperm motility and sustainability. The same chemicals were also found in a range of commercial dog foods, including canned, dry and puppy formulas. From the study:

“ECs [environmental chemicals], including diethylhexyl phthalate (DEHP) and polychlorinated bisphenol 153 (PCB153), were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species.

Testicular concentrations of DEHP and PCB153 perturbed sperm viability, motility and DNA integrity in vitro but did not affect LH stimulated testosterone secretion from adult testis explants. The direct effects of chemicals on sperm may therefore contribute to the decline in canine semen quality that parallels that reported in the human.”7

These chemicals leach into commercial pet food from packaging, and from contamination of plants and livestock.

How to Cleanse Your Dog’s Body of Chemical Contaminants

The chemicals discussed above, and others are pervasive not only in homes, but also in plant and sea life, and food animals as well. If you’re concerned about contaminants in commercial pet food, my advice is to make nutritionally balanced, species-appropriate dog meals at home using as many fresh, organic ingredients as you can afford. An alternative would be to purchase commercially available, human-grade, fresh or dehydrated, or freeze-dried organic pet food.

It’s very difficult to avoid all environmental toxins these days, and there are many different ways our pets are exposed. If you're wondering if your own dog is carrying a toxin load, unfortunately there's no doubt about it. The truth is that virtually every pet has measurable amounts of chemicals in their body. That’s why I recommend periodic detoxification depending on your dog’s level of exposure to toxins.