Man’s – and Microbiome’s – Best Friend

Perhaps the most unconditional love we experience is from our dogs. Dogs see us at our best and our worst and never falter in their loyalty and affection. They are faithful companions, cuddly sleeping partners, energetic exercise buddies, and great listeners. More broadly, dogs can significantly aid in managing and mitigating their owner’s depression, and studies have shown that therapy dogs can reduce human symptoms of a variety of ailments, including anxiety, pain, high blood pressure, and even cancer. Recent research shows that the healing power of dogs may go much deeper: all the way to our gut.

Studies have found that dogs were domesticated somewhere between 32,000 and 10,000 years ago, and, during our time together, humans and dogs have shared more than just emotional bonds. We’ve also shared bacteria, including the protective effects of the microbiome for human (and canine!) health.

The advancing science of genetic sequencing has enabled researchers to investigate the dog microbiome more closely to determine its similarity with that of humans. A look into this research reveals how the microbiome can affect not only the health of our canine friends, but also the surprising potential benefits to their human companions.

It’s not only humans who depend on the microbiome

Like humans, dogs have a distinctive microbiome across their body sites, with different bacteria present in the mouth, in the digestive system, and on the skin. Canine microbiomes are highly diverse, with the most diversity concentrated around their noses (think of your dog’s nuzzles as a microbiome boost). Just as every dog is unique, their microbiomes are unique, as well. Diet, genetics, antibiotic exposure, and environment can all determine the bacterial makeup of a dog’s gut.

Researchers have begun investigating the role of dogs’ microbiomes in their health, too. Disturbances in the canine microbiome have been found to possibly trigger allergies, skin conditions, inflammatory bowel disease, and other illnesses.

Humans and dogs share more than just friendship—they share bacteria

As close as you are to your dog, your microbiomes may be even closer. According to one 2013 study, cohabitating family members share bacteria from their skin microbiomes with each other—and with their dogs. In fact, just having a dog could increase the similarity of your microbiome to that of other dog owners, even if you don’t live together. Families with dogs also had the highest levels of similarity and shared more skin microbiota with one another than families without dogs. Looks like having a dog really does bring the family closer to each other.

Much of this microbial closeness is due to environmental factors. Scientists hypothesize that simple skin-to-skin transfer accounts for a lot of this bacterial sharing. Humans and dogs also exchange bacteria through the air, which has such a pronounced effect on household dust that researchers are able to predict whether or not a household has a dog or cat based only on a bacterial sample from the home.

There’s could be an even deeper explanation for the bacterial similarity between you and Fido, and it lies in the long history of canine-human cohabitation. Dogs, in general, have a more similar gut microbiome to humans than other mammals, sharing 26 percent of gut bacteria with humans. Scientists theorize that this is due to the long, collaborative history between dogs and humans.

How your dog’s microbiome benefits your health

You make sure to take good care of your dog’s health—but did you know that your dog’s microbiome could have a positive impact on your health, too?

There’s increasing evidence showing that bacteria from a dog’s microbiome may boost a human’s immune system. In fact, children in households with a dog have been found to have a reduced predisposition toward allergic reactions, perhaps due to the presence of common canine bacteria Ruminococcus and Oscillospira. In fact, your family dog may have helped lower your risk of allergies even before you were born, as prenatal exposure could lead to decreased IgE levels (the chemical indicating allergic reaction) in infants. The canine microbiome is so potent, a 2014 study found that even exposing mice to dust from a dog-owning household gave the animals increased protection against airway allergens.

The similarities between canine and human’ microbiota also make dogs great candidates for microbiome research. One study of the dog gut microbiome demonstrated that, just like in people, obese dogs’ gut microbiomes respond significantly to high-protein/low-carbohydrate diets—indicating the possibility that future research on the dog gut could be extrapolated to humans.

So next time the family dog jumps on you for affection or gives your toddler a big, sloppy kiss, think of life with your dog as an exchange of love and immunity. After tens of thousands of years together, it’s good to know that man’s best friend has our back (and our gut).