Can Your Dog Improve Your Biome?
The relationship between man and dog goes back thousands of years, and they didn’t become ‘man’s best friend’ for no reason. Dogs are intelligent, loving and friendly, which is why they are one of the most popular pets – in the U.S around 40% of households own a dog.
The bond between man and dog is as strong as it ever was because humans and dogs can benefit from each other. We feed our dogs and walk them, and in return they offer us unconditional love and countless health benefits. For instance, studies have found that people who own dogs are less likely to die of heart disease than those who don’t.
However, recent research has found that dogs benefit us in even more ways than we think; a 2013 study at the University of Colorado found that humans share microbes with their dogs, but that isn’t all. The same study found that couples who live together are more likely to share their microbes with each other if they owned a dog.
Why does this happen? It may have something to do with how adorable your dog is; one person is likely to pet and cuddle their furry friend, leaving their microbes on their pet’s fur. Later when the other partner pets the same dog, they pick up microbes from both the dog and the other human.
This is great news for anyone who owns a dog, as varied microbiome is beneficial to your health. Our bodies contain around eight million genes, but only about 0.3 percent are human. The rest are created by our microbiomes, and they coat our skin, mouth, gut-lining, and just about anything else that you can think of.
These genes are made up of bacteria, viruses, fungi and yeasts, and they all contribute to our overall health – the less varied our microbiome is, the more likely we are susceptible to diseases. Lots of things can affect our microbiome, including our diet, antibiotics and who we live with.
Who we live with is actually a big factor for our microbiomes. A person may only have 10 percent of their microbiomes in common with a stranger, but they will have far more number of similar the microbiome population with people that they live with – and research has found that this also includes dogs.
You and your dog share microbial population – so can your dog affect your health?
A recent study has found that dog owners share skin, tongue, and gut microbes with their dogs. The study aimed to find out more about how the people and pets you live with can affect the microbes living in your body.
Researchers from across the U.S looked at 17 families with parents and children ranging from babies to 18 year olds, 17 families with one or more dogs but no children, 18 families that had both children and dogs, and 18 couples who didn’t have dogs or children.
Each family sent in swabs that they had rubbed on the palms of their hands, their foreheads, their tongues and their feces so that the researchers could analyze their microbiomes. The families also sent in swabs of their dog’s paws, tongue, and fur so that the researchers could compare microbiomes to find similarities.
They found that families share similar microbes on all parts of their bodies, and that the skin microbes were most alike, showing that people share microbes with each other when they touch each other, or when they both touch the same surfaces. Adults had the most shared microbes, which makes sense as they are older and have cohabited together for longer than the children.
Interestingly, parents only shared microbes with their children if the children were older than three. This is because younger children have very different microbes to adults as they are still developing.
A dog has a large effect on his humans’ overall microbes. People who own dogs have more microbes in common with other dog owners than they do with people who don’t own dogs, so it is clear that humans are affected by dog microbes.
You may be wondering what the differences are between human microbes and dog microbes. Dogs have more diverse microbes than humans, including microbes that are normally thought of as ‘human’ microbes. They also have a more diverse range of microbes that live in soil and water. One microbe that dog owners share with their pets is Betaproteobacteria, which is found on human skin and – you guessed it right – on dog tongues. This microbiome is passed between the pet and its owner every time the dog gives their owner an affectionate lick.
Now we know that dog-owners share microbes with their dogs, more questions are raised. Is there microbiome health benefits to owning a dog, and if so, what are they? Does a pet dog also work as a probiotic for the owners?
Two fascinating studies seem to have found the answers to these questions. The first study was conducted in 2013 by UCSF scientists, and it found that babies and toddlers who live with dogs may have a lower risk of developing asthma and allergies, which is an obvious health benefit. This is because they have been exposed at a young age to “dog-associated house-dust” – and if you own a dog, you’ll know exactly what that means.
Dogs shed their fur and dander, which is a combination of fluff and skin, and most surfaces in their homes will have dander on them. The children touch these surfaces and then the microbes are transferred to their skin, hair and mouth to expose them to new types of microbiome. Researchers believed that this exposure to harmless bacteria “trains” their developing immune systems.
The second study is very heart-warming; it is trying to find out if dogs can directly improve the health of people over 50.
Research aims to find out if dogs can directly improve the health of older people
Researchers from the University of Arizona are currently completing a study exploring whether dogs can improve human health by having a probiotic effect on the body. All of the participants are over 50 years of age; and hence, this will be looking at the effect of dogs on older people.
The researchers are testing the theory whether good bacteria from dogs can be transferred to the owner so that the owner gets health benefits from their pets.
To get dogs for the study, researchers adopted 50 unwanted dogs from the Humane Society, and gave them to people who have never owned a dog, or haven’t had a dog for the last six months. This lack of exposure to dogs will make it easier for researchers to see if there are any differences. It was also seen that the participants haven’t taken antibiotics for the past six months.
It is also notable here that participants will have the option to adopt the dog they live with at the end of the research.
The participants will live with the dog in their houses for three months, and researchers will evaluate the participant’s gut bacteria and immune function. The dog’s gut bacteria will also be evaluated, and there will be follow-up evaluations at the end of each month to look for any positive results. The researchers are also looking out for changes in the emotional well-being of both the people and their dogs.
The research is in-depth and aims at monitoring the physical and mental health of the owner and the dog and look for improvements.
"We've co-evolved with dogs over the millennia, but nobody really understands what it is about this dog-human relationship that makes us feel good about being around dogs," said Doctor Kim Kelly, one of the primary investigators on the study. "Is it just that they're fuzzy and we like to pet them, or is there something else going on under the skin? The question really is: Has the relationship between dogs and humans gotten under the skin? And we believe it has."
The human digestive system contains more than 500 different types of bacteria, some are good for you, others are not. Probiotics are often classed as “good” bacteria as they assist in digesting food and they help maintain your immune system. Because of this, people often buy probiotic yoghurts in to help their immune system. However, it is likely that dogs are more beneficial for humans’ immune systems than probiotic yogurts.
"We essentially want to find out, is a dog acting like yogurt in having a probiotic effect?" said Kelly.
"We think dogs might work as probiotics to enhance the health of the bacteria that live in our guts. These bacteria, or 'microbiota,' are increasingly recognized as playing an essential role in our mental and physical health, especially as we age," said Dr. Charles Raison, principal investigator for the study.
"We know that not all bacteria are good. We can get very sick from 'bad' bacteria, and modern medicine has done a wonderful job of protecting us from various diseases that are created by these bacteria," said Raison. "But unfortunately, by eliminating the bad bacteria we've started eliminating the 'good' bacteria, too."
The study is the first of its kind; it is the first study conducted under the UA’s new Human and Animal Interaction Research Initiative. They aim to bring together researchers from across many fields to explore the mutual benefits of human and animal relationships.
For hundreds of years humans have talked about the benefits of living with dogs, and research has shown that people with dogs are generally happier, less stressed and less likely to die of heart disease. However, there is little research into why this actually happens, and this research aims to find out more.
The Human-Animal Interaction Research Initiative (HAIRI) was started by husband-and-wife research team Dieter and Netzin Steklis.
"Our emphasis with HAIRI is first to bring good rigorous science to understanding the relationship between humans and non-human animals," said Netzin Steklis. "Then we can use that to contribute to the education of, for example, future veterinarians or family therapists or the pet industry. We want to extend this research into practice through education and outreach."
"What's driving most of our work is our love of animals, our interest in animal behavior, and how co-evolutionary processes have shaped our minds and the minds of animals," said Dieter Steklis. "We've had experiences, personal and scientific, with many non-human animal species—wild, tame and domesticated. For now we have our own horses and dog, but we've always had a variety of animal friends in the family. Through HAIRI, we want to bring together collaborators from all different areas of expertise to work on these important projects that will inform our future relationships with animals."
This research is likely to discover the links between dog microbiomes and human microbiomes. In comparison to humans, dogs have quite simple gut bacteria, but they have complex oral microbiomes. Researchers previously examined samples from the mouths of 50 dogs, and they found 353 different types of bacteria – and over 80% of them didn’t even have names!
We have very different oral bacteria than dogs – only 16.4% of the total types of bacteria were found in the mouths of humans.
It is clear that dogs benefit humans emotionally and physically, but it is often difficult to see exactly how. Now research has found babies who are raised in homes with dogs are less likely to suffer from allergies and asthma, offering proof that dogs can benefit children.
The research that found that dog owners share microbiomes with their dogs is also very important. This links to the other research, as it is this exposure to dog microbiomes that helps to prevent allergies and asthma. Further research is needed in this area, but the results are obvious – giving your dog a cuddle can benefit your immune system, so if you have a dog, go give him a cuddle now!
Alexandra Carmichael. “What Happens to Your Microbiome If You Own a Dog?” January 11, 2016, uBiome blog. <http://www.ubiomeblog.com/what-happens-to-your-microbiome-if-you-own-a-dog/>
Alexis Blue. “Could man's best friend be man's best medicine?” March 17, 2015, Phys Org. http://phys.org/news/2015-03-friend-medicine.html
Francie Diep. “HUMANS SHARE MICROBIOMES WITH THEIR DOGS, STUDY FINDS” April 18, 2013, Popular Science. http://www.popsci.com/science/article/2013-04/humans-share-microbiomes-their-dogs-study-finds
Heather Buschman, PhD. “Man’s Best Germs: Does Your Dog Influence Your Health?” https://health.ucsd.edu/news/features/Pages/2015-05-07-mans-best-germs-your-health-and-your-dog.aspx
Song SJ, Lauber C, Costello EK, et al. “Cohabiting family members share microbiota with one another and with their dogs.” Weigel D, ed. eLife. 2013.<http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3628085/>