Scientists in the US are recruiting volunteers to help them investigate the health benefits of living with a dog - specifically, are the microorganisms they share with you having a positive effect on your mental and physical health?

"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," lead researcher and anthropologist Kim Kelly, from the University of Arizona, said in a press release. "The question is: Has the relationship between dogs and humans gotten under the skin? And we believe it has."

The hypothesis is based on previous research that has found that dogs and their owners grow to share the same types of gut bacteria after living with each other for some time. Because a healthy population of micoorganisms is essential to physical and mental health, particularly in later life, the team wants to figure out if dogs are unwittingly helping their owners achieve this.

There is also epidemiological work showing that when young children and infants are in frequent contact with dogs, they have a reduced risk of developing immune disorders, such as asthma and various types of common allergies, which could also be linked to microbe-sharing.

Kelly’s team are now looking for volunteers with dogs to be studied over a three-month period, during which time their gut bacteria, diet, physical activity levels, and immune function will be assessed. Each dog will have its physical activity levels and gut bacteria analysed at the same time.

The volunteers must be strictly 50 years or older, healthy, have not taken antibiotics in the past sixth months, or lived with a dog. This means they’re essentially starting from scratch, so any effects their new dog pals have over the three-month period should be easy to spot. The team chose to work with older participants because research has shown that, in people over 65, a poor microbiome could mean death, so it's important to figure out all the means available to ensure good microbiome health in this age group.

Follow-up evaluations will take place after one, two and three months to look for any positive impacts on gut microflora in either the humans or the dogs. Researchers also will note any changes in the mental health and emotional well-being in both the humans and the animals. The team will try to figure out if the presence of a dog and the sharing of its microbiome actively encourages the growth of more positive micoorganisms in their owners’ guts so significantly that it could have a marked effect on their physical and mental heath.

"We essentially want to find out, is a dog acting like yogurt in having a probiotic effect?" said Kelly.

We can't wait to see the results. When you think about it, the idea that dogs are being our best friends in ways they aren't even aware of is pretty special.