If you think all dogs are cheerful, upbeat and excited about what life has to offer, you’ve either interacted exclusively with optimistic dogs, or you haven’t noticed that some dogs are a little more on the “food bowl half empty” side of the personality spectrum. Not all dogs are quite as happy-go-lucky as we humans generally assume.

The idea of individual personalities in dogs is hardly stop-the-presses news anymore, but studying such differences in dogs is still a fruitful area of research. In a 2014 study published in PLOS, a group of scientists studied judgment bias in dogs to investigate individual tendencies to view the world optimistically or pessimistically.

To study dogs’ expectations of the world, they trained them to associate different sounds with different outcomes. One sound let them know that touching a target would result in receiving the preferred reward of milk. The other sound, two octaves apart from the milk sound, indicated that they would get the less desirable reward of an equal amount of water. The correct response to the water tone was not to touch the target. Once dogs could easily distinguish between these two sounds, the real test of their personalities began.

Trained dogs were given a tone that was between the two trained tones, and their response was observed. Dogs who reacted to the ambiguous tone by pushing the target in anticipation of milk were considered optimists. They expected good things to happen. Dogs who failed to respond to the ambiguous tone were considered pessimists in that they did not have an expectation of good things. They were not filled with the hopefulness of the optimists in the study. This study allowed researchers to determine whether individual dogs have the expectation of positive outcomes or whether they expect negative outcomes.

Some dogs would respond to ambiguous tones even if they were more similar to the water tone than to the milk tone. These dogs were considered extreme optimists. Overall, researchers found that more dogs were optimists than pessimists. I find that reassuring since it matches the way most of us view dogs.

What do you think this test would reveal about your dog?

A new report by researchers at U.C. Davis points to the need for oversight of nutrition supplements. The pills and powders fed to pets to boost their health come with no assurance of getting what you pay for—or more than you bargained for, like toxic contaminants.

In this case, a tainted organic algae powder was damaging the liver of an 11 year old Pug, who lost her appetite and was lethargic after several weeks use. The authors say it’s the first documented case of blue-green algae poisoning in a dog caused by a dietary supplement. (Most reports of illness involve dogs exposed to water containing certain blue-green algae toxins.)

Blue green algae supplements are sometimes fed to dogs to relieve arthritis or boost the immune system.

Many consumers believe these products can only be sold if they are safe for use, the authors say. “Unfortunately, the opposite has been demonstrated in several studies showing the contamination of blue-green algae supplements with microcystins.”

With the use of commercial health products on the rise, the risk is growing. While supplements are regulated by the FDA, there are no requirements for proving them safe or effective before marketing. That is, the industry “is largely self-regulated,” the report says.

Toxic blue-green algae blooms occur in Oregon’s Klamath Lake, where supplement manufacturers harvest much of their source material. In 1997, the state became the first to regulate the amount of mycrocystins allowed in supplements.

Adrienne Bautista, the lead researcher on the current report, says in an email that the tests may not catch every problem. The tests many companies use to certify their products are below the 1 ppb Oregon limit are often ELISAs, Bautista says, which mainly detect “the LR congener of microcystin.” But there are more than 100 other congeners likely to have similar modes of action that the tests are “quite poor” at finding. So even if the supplement tests below the 1ppb for this common toxin, others may still be present.

What could lower the risk from these particular supplements is to produce the algae in a lab-like setting, Bautista says. “By harvesting it naturally, you have no control over contamination from other algae.” 

The researchers call for stronger oversight of dietary supplements for companion animals, and greater awareness among veterinarians.

With treatment and by stopping the supplement, the Pug made a full recovery.

The microbiome is the invisible world of the hundred trillion bacterial, viral and fungal microbes that live on us and in us—on our hair and skin, behind our ears and inside our eyelids. The bulk of these miniscule microbes are good guys, gut microbiota that congregate in the digestive tract, where they bolster the immune system, manufacture vitamins and digest food to generate nutrients and energy.

Microbial equilibrium is a delicate balancing act, and a broad spectrum of inflammatory and autoimmune diseases is linked to having too many microbes—or too few. For example, researchers know that significantly lower bacterial diversity is found in both people and dogs with chronic inflammatory bowel diseases.

Teasing out the biological interaction of trillions of miniscule microorganisms that colonize the body, and the role they play in well being, is a new frontier. Will it be a watershed moment in veterinary medicine? Scientists are hopeful. The human microbiome has become a hot topic in biologic investigations, and canine research is fast catching up, much of it inspired by the success of the Human Microbiome Project, launched in 2007 by the National Institutes of Health (NIH). Using stool and tissue samples to isolate microorganisms, researchers are mapping the diversity and normal profile of the human microbial community.

Another undertaking, the Human Food Project, invites the public to submit personal and family microbial samples along with samples from family dogs to better understand how a person’s microbiome compares to that of animals living in the same environment. (The project’s dog segment has been discontinued.) The analysis centers on the anthropological co-evolution of humans, animal and plant microbes to understand modern disease against the backdrop of our ancestral/microbial past.

It’s all about dogs at Companion PBx, a new startup that primarily targets the canine digestive tract. Its goal is to build a cumulative gut flora database and develop dietary products customized for dogs’ digestive health. In January 2015, the company launched a Kickstarter campaign to raise money for construction of the database.

According to Companion PBx Chief Science Officer Kelly Scott Swanson, PhD, who’s on the faculty at University of Illinois, Urbana-Champaign’s Department of Animal Sciences, “By sequencing the microbes in your pet’s sample, we obtain a fingerprint of the microbial community in your pet’s GI tract.”

Microbes in Common

Affected by age, environment, ancestry, evolution, genetics and diet, microbial communities vary widely between species and across individuals within a species. A recent study suggests that our housemates—including the family dog—may also affect the composition of our personal microbial signature.

If you and your significant other kiss, hug and/or share a bed with your dog, the three of you have more in common than you think. A study conducted by researchers at the University of Colorado, Boulder, revealed several similarities: Adults who share a dog have more similar mouth microbes than those who don’t. Dog-owning families have more diverse and different microbial colonies than dogless households. Parents tend to share more kinds of mouth bacteria with their dog than they do their children. And children raised with dogs have a wider variety of microbes than dogless kids (Song et al. 2013).

Whether these spit-swapped microbes serve a purpose or are just passing through is not clear. But research shows that children raised with dogs are less likely to be afflicted by eczema (Epstein et al. 2010) and asthma (American Society for Microbiology 2012).

The notion that microorganisms in the canine gastrointestinal tract might have unique properties is not new. Early Romans understood the medical value of a well-run therapy dog program. Health temples, the ancient equivalent of modern-day outpatient clinics, were staffed with live-in cynotherapists, gentle dogs who wandered about the grounds greeting patients and licking wounds. Were the dogs healing only psychosomatic injuries? Time and additional research funding will tell.

The idea that our microorganisms may to some extent be collectively beneficial is intriguing. People and dogs have been exchanging microbes for at least 30,000 years, since the first little cave girl kissed the first proto-dog puppy smack on the muzzle. That’s a long history of sharing. It’s possible that our microorganisms are at least symbiotic, and perhaps even played a role in the dramatic domestication of the dog.

Theoretically, many thousands of years ago, a population of carnivorous wolves or ancient proto-dogs (depending on where you stand in the dog-domestication debate) transitioned from a meat-heavy diet to one laden with grain, a consequence of the agrarian revolution.

Scientists know that the acquisition of a new diet is a fundamental driver for the evolution of a new species (Dale, Moran 2006). When species transition from carnivorous to omnivorous diets, the gut microbial community co-diversifies with the host and drives further evolution (Ley et al. 2008). As human diets changed, so too did those of Canis familiaris. Over time, as we incorporated these unique animals into our daily lives, we continued to reshape them.

Challenges

In humans, autoimmune and inflammatory diseases are on the increase. Scientists can’t verify a similar pattern in dogs because epidemiological studies are rarely conducted in veterinary medicine. Additionally, many autoimmune conditions are diagnosed based on the patient’s subjective description of symptoms.

But this is not the case with itchy skin. Dogs who scratch themselves incessantly are highly likely to have allergies. When researchers compared microbial colonies on the skin of healthy dogs to those of dogs with allergies, they found that non-allergic dogs have much richer and diverse skin microbial communities (Hoffmann et al. 2014).

But when it comes to proving causality, scientists wisely err on the side of caution. It’s not understood if a change in the microbiome causes certain conditions, or if it occurs as a consequence of the conditions. Nor is it absolutely clear that more diversity is better than less. At this point, scientists cannot say with confidence exactly what a healthy microbiome should look like in the dog.

Moreover, what seems logical may not be so. For instance, anyone who has lived with a poop-eating pooch has wondered why some dogs do and other don’t. Are coprophagic dogs seeking microbes lacking in their gut? Surprisingly, research involving mice suggests that this might not be the case; coprophagia in germfree mice is the same as in conventional lab mice (Ebino et al. 1987).

Other questions arise: Are the microbiomes of individual dog breeds more similar to each other than they are to those of other breeds? And could these isolated microbial communities drive breed-specific ailments?

Jan Suchodolski, DVM, a Texas A&M veterinary medical and biomedical sciences researcher who studies dog and cat gastrointestinal diseases, says that this doesn’t seem to be the case. As he noted, “So far, we do not have any clear evidence that gut microbiomes are more similar within breeds. Environmental influences such as age, diets and antibiotics, and especially the effects of GI disease, are larger than any breed effect.

“It may be possible that we missed an effect, as we have not evaluated thousands of animals. But if there were a breed effect, it would probably be very minor. Even within puppies of the same litter, the microbiome shows huge inter-animal variation, so the animal effect is much stronger than any other effect.”

Idiopathic canine inflammatory bowel disease (IBD) is a gastrointestinal condition in which the digestive tract is chronically inflamed. Symptoms include vomiting, diarrhea and weight loss. Dogs with IBD have significantly lower bacterial diversity as well as microbial communities that are distinct from those of healthy dogs. In 2014, Dr. Suchodolski and his colleagues conducted a study of 22 companion dogs, half of whom suffered from idiopathic IBD (Minamoto et al. 2015). They wanted to know if traditional treatments—steroids and special diets—directly or indirectly created a more robust microbial community.

After treatment, the sick dogs felt a lot better. However, there was no change in their gut microbiota. The researchers concluded, “This study demonstrates intestinal dysbiosis [microbial imbalance] and altered serum metabolite profiles in dogs with IBD. But medical therapy doesn't seem to affect the intestinal dysbiosis.”

It could be that, rather than triggering the condition, microorganisms are compromised by it. Researchers also suspect that biological environmental stresses are involved in ways not yet understood. Dr. Suchodolski added, “It may be that we need longer follow-up periods of treatments to see potential improvements. Another reasonable theory is that with the current standard therapies—for instance, immunosuppression—we just control clinical signs, but the underlying etiology of the disease is ongoing.”

Culprits

When it comes to treating dogs for myriad problems, vets often prescribe antibiotics, and for good reason: antibiotics save lives. But the war on infection sometimes puts good bacteria in the line of fire, too. When assaulted by repeated antibiotic use, some classes of gut bacteria struggle to recover. If the affected bacteria play a pivotal role in autoimmune health, overuse of antibiotics may coincide with a decrease in healthy autoimmune responses.

Antibiotics are not the only culprits. Scientists suspect that in human births, Cesarean deliveries may contribute to an increase in autoimmune weaknesses as well. In a vaginal birth, the fetus departs the womb without a single microbe but acquires them by passing through the mother’s birth canal. By the time the newborn takes his first breath, he is covered with colonies of bacteria that kick-start his immune system, establish a healthy digestive tract, help shape his growing brain and even protect him from psychiatric disorders. C-section babies start life without the microbes they would have picked up from vaginal delivery, suggesting that the colonization of the newborn might be delayed (Jakobsson et al. 2014).

Medical disorders connected to non-vaginal delivery and the slow introduction of protective bacteria have not been studied in the dog. Considering that a number of breeds with exceptionally flat, wide skulls—such as the Boston Terrier, French Bulldog and Bulldog—must have their pups delivered via C-section, it’s an area that deserves further study.

Or is diet the problem? Commercially manufactured dog chow was introduced in the U.S. in the mid-1920s. By the 1950s, processed dog food like Friskies, Sergeant’s and Purina were widely available through local grocery stores. Today in the U.S., we spend more than $10 billion a year on commercial pet food. The question arises: has the increase in autoimmune diseases paralleled the rise in popularity of processed dog food?

Because veterinary practices typically don’t collect this type of empirical data, the answer is, at best, a guess. But many dog owners think so, and have eliminated or cut back on processed foods in favor of raw meat and vegetables. However, as of now, there is no definitive evidence to show that fresh foods modulate the gut microbiota.

Cures

Sophisticated DNA sequencing technology has opened up the invisible world to scientific scrutiny. But determining its impact on the host species is difficult and time-consuming. Researchers need to locate and identify a microbe’s fingerprint, then remove a sample and grow it in a culture, a process especially difficult with shyer microbes that are destroyed by oxygen or stomach acid.

To figure out why we get sick and the role microbes play in illness, researchers must first determine how these trillions of organisms interact with each other. And the fact that scientists can prove a problem exists doesn’t mean they know how to fix it.

Developing therapeutic dog foods that target specific vulnerabilities may help, but will take time to develop. Although the probiotic movement may oversell their benefits, probiotics (friendly bacteria like those that live in the gut) are effective in some cases. And prebiotics, foods that encourage growth of good bacteria already present, may help as well.

The University of Pennsylvania School of Veterinary Medicine (Penn Vet) is recruiting dogs with acute symptoms of diarrhea and/or vomiting for a new clinical trail that will evaluate the role of the intestinal microbiome—the community of “good” bacteria that live in the gut—on chronic gastrointestinal diseases. Therapy will include simple diet change, treatment with antibiotics or combination therapy with steroids for more complicated cases.

Penn Vet researchers anticipate that their study may reveal how gut microbiota influence and respond to treatment, which in turn could lay the groundwork for future projects using treatments such as prebiotics, probiotics or fecal transplants (transferring “good” microorganisms from a donor’s healthy stool to the patient’s gastrointestinal tract). According to Research Assistant Professor Dr. Daniel Beiting, “Whereas past studies have used a single method to sequence bacterial DNA, the Penn Vet study will use a more sophisticated approach called metagenomics, generating a much more comprehensive catalog of bacteria in the stool and providing insight into what they might be doing.”

Penn Vet is currently looking for dogs with chronic gastrointestinal problems. People interested in enrolling their dog in the study—Evaluating the Role of the Microbiome in the Resolution of Canine Chronic Enteropathy—should email Penn Vet’s Veterinary Clinical Investigations Center at vcic@vet.upenn.edu, or call (215) 573-0302.

Future possibilities are exciting. In the meantime, kiss your dog. It’s good for you in more ways than one.

If you live with a dog, chances are you’re familiar with canine de-stressing techniques. Perhaps you’ve felt a wave of relief from burying your face in fur after a difficult day at work, or experienced a release of calming chemicals after being met with a particularly enthusiastic greeting. And maybe those daily dog walks have helped you shed a few pounds or led to some welcome social interactions with other people and their dogs. And doesn’t life seem to have more meaning because there’s a living creature depending on you?

To dog people, the emotional, physical and even spiritual benefits of canine relationships tend to be obvious. These benefits feel as real to us as the saliva-soaked tennis ball we’re holding in our hands. That’s why it can be so hard to understand why the non-dog world hasn’t caught on to all these life-altering advantages. Even worse is the fact that many people who have never lived with a dog seem to think we may be making all this up—that the only place these benefits exist is in our heads.

Science in Action

Thanks to a special report from Harvard Medical School (HMS), we now have something important to share with these nonbelievers—proof! Get Healthy, Get a Dog is the first publication to compile hundreds of research studies from around the world that document the physical and psychological benefits of dog ownership. Taken together, these studies provide the most complete picture yet of the many ways in which dogs enrich human life: from lower cholesterol and improved cardiovascular health to weight loss, companionship, defense against depression and longer lifespans.

“The most common reaction we’ve been getting from people about this report is that they are so grateful that someone has finally put into print what they’ve known intuitively all along,” said medical editor Elizabeth Pegg Frates, MD, who supervises the Lifestyle Medicine Interest Group at HMS, teaches a college course on lifestyle medicine at the Harvard Extension School, and directs the Wellness Programs at the Spaulding Stroke Research and Recovery Institute, an HMS affiliate.

The 50-page report is the result of a collaboration between HMS and Angell Animal Medical Center, a leading veterinary hospital based in Boston. Get Healthy, Get a Dog approaches the dog/human relationship as a two-way street, so half of it is devoted to the human—what the dog does for the person—and half is devoted to the dog—what the person should do for the dog. Frates tackled the former, and Lisa Moses, VMD, who heads the Pain Management Service at Angell Animal Medical Center, covered the latter, which includes sections on nutrition, exercise, training and responsible pet ownership. Moses also makes a compelling case for adopting a dog rather than going to a breeder or pet store.

“We didn’t want to create the impression that a dog is some kind of tool for achieving better health,” says Moses in explaining the dual focus. “We wanted to emphasize that it’s the relationship that provides these benefits—it’s not the pet. And for that relationship to develop and be sustained, you have to do your part.”

Physical Benefits 

Doing your part often means going for walks in the rain, sleet or snow, at all hours of the day and night. In fact, one of the primary health benefits of owning a dog is that it boosts your activity level. There have been about a dozen studies conducted on the link between dogs and human exercise, including one that compared 536 dog owners with 380 non-owners. Those with dogs were found to be fitter, thinner and less likely to have chronic health conditions, such as high blood pressure and diabetes. A study in Missouri that paired public housing residents with certified therapy dogs for five 20-minute walks a week found that participants lost an average of 14.4 pounds without changing their diets. (The report points out that most weight-loss programs and anti-obesity drug trails can’t boast such good results.)

Of course, the fact that regular exercise helps people lose weight and get healthy isn’t exactly breaking news. The insights come from the critical role the dog plays as a fitness partner—offering everything from enthusiastic encouragement to obnoxious pestering. Unlike a human partner, a dog is not going to suggest ducking out to a movie. “The dog support was always positive, while the human support could be positive (friends, family), negative (saboteurs) or inconsistent,” wrote Frates. Another reason that people tend to adhere to an exercise program if a dog is involved is the perception that the dog needs them. In one study, 72 percent of participants cited this as the reason they stuck to the activity schedule for the full 50 weeks of the trial.

“Sometimes people find that the dog becomes the excuse for taking care of themselves,” says Moses. “It may not be acceptable to them to be so self-oriented, but if it’s about the dog, then it’s okay.”

The American Heart Association (AHA) uncovered another piece of canine magic: a dog appears to help someone who is obese overcome his or her embarrassment about being seen in public doing physical activity.

It’s likely that increased exercise plus the calming effects of dogs (which we’ll get to later) contribute to lowering blood pressure. One study actually tested dog ownership as a treatment for high blood pressure. Thirty people with borderline hypertension were randomly assigned to either adopt a dog right away or defer adoption to a later date. After five months, the segment of new dog owners experienced significant declines in systolic pressure (the top number, which measures the highest arterial blood pressure). The group that had been asked to defer adoption experienced these same declines once they had taken their new dogs home and spent time with them. In 2013, the AHA went as far as to say that pet ownership “is a reasonable strategy for reducing heart disease risk.”

And there’s more good news on the cardiac front. A study of nearly 6,000 men and women in Australia found that dog owners of both sexes had lower triglyceride levels than non-owners, and male dog owners also had lower total cholesterol levels.

Emotional Benefits 

Beyond these formidable physical benefits are the psychological ones, which according to Frates “are hard to overstate.” Dogs make us feel less isolated. They pull us into a social world inhabited by other people walking other dogs. (Seventy percent of dog walks lead to at least one spoken interaction with a stranger.) And they help us meet the basic human need for companionship. Two large, long-term studies that followed people from childhood to old age found that those who were more engaged with others—whether those others were people or animals—lived longer. Those longer lives may also be more purposeful. A dog’s total dependency can make that person feel wanted and give life a sense of meaning.

Moses knows this phenomenon first hand. Her grandfather spent more than a decade as primary caretaker for his wife, who suffered from rheumatoid arthritis and cardiovascular disease. During all those years, he had a succession of dogs to care for—or was it the other way around? After his wife died, his beloved Terrier mix Lady succumbed to kidney failure. “At age 92, unbeknownst to us, he went out and adopted another dog,” Moses says. “Having a dog was the reason he got up in the morning. It was his entire life. He was a living testament to the power of the human/canine bond.”

There are other indicators that dogs are particularly helpful to older people. The HMS report cites a year-long study from Canada that found elderly dog owners to be more capable of performing daily activities, such as dressing and feeding themselves. This is likely because in attending to their animal companions, seniors are reminded to take care of themselves. They also have a structure in place, thanks to the need for regular pet meal times and walks, which reinforces their own self-care habits.

At the other end of the age spectrum, children learn important life skills from early bonding with the family dog. That bonding can lead to stronger human connections later in life, according to a Tufts University study, which also found that kids who’ve forged emotional connections to dogs have more empathy, feel more self assured and do better in social settings.

“How else would you get your kids to touch and love something?” asks Frates, the mother of two teenage sons. “For boys especially in this culture, there are very few acceptable ways of encouraging this type of bonding and intimacy.”

There is even evidence that exposure to a dog from infancy onward reduces the likelihood that even the most allergy-prone kids will develop problems. Only 19 percent of babies living with dogs developed pet allergies, compared to 33 percent of babies who grew up in dog-free homes, according to one study.  

As those babies grow up and become college students, the dog benefits continue. Several psychological studies have found that college-age adults tend to find more stress relief in turning to their dogs than in seeking comfort from parents or siblings. Still other adults were found to shake off the blues just by thinking about their dogs … which brings us to the magic of oxytocin.

Canine Rx

Having a dog can be like having your own a prescription for oxytocin with unlimited refills—except that rather than dispensing this drug, your dog incites you to release it. Also known as the “love,” “bliss,” and “bonding” hormone, oxytocin inspires positive feelings. It helps stave off depression and limit the release of the stress hormone cortisol. You can get an oxytocin infusion by petting your dog, by laughing at the silly things she does, and even by looking into her loving eyes, a conclusion confirmed by recent study

Dogs also offer an alternative to meditation sessions and yoga classes when it comes to learning the Buddhist practice of mindfulness. Every dog walk is typically an exercise in experiencing the present moment: savoring an especially aromatic fire hydrant, having a satisfying roll in the grass or interacting with a new neighbor. Dogs put us more in touch with nature and help us put aside our worries about the future and regrets about the past to focus on the here and now.

While all the information contained in Get Healthy, Get a Dog has been meticulously reviewed and objectively compiled, Moses and Frates are hardly dispassionate observers. Both say their lives have been greatly enriched by their relationships with their dogs. They do, however, come from very different ends of the dog spectrum. Moses, who shares her home with a rescue named Rudy, describes her love of canines as developing “in utero.” This was due largely to the influence of her grandfather and the fact that he treated his Beagle mix, Friday, like one of the grandchildren.

Frates, on the other hand, was terrified of dogs after being bitten on the shoulder by a Doberman. The experience, which happened when she was eight years old, was so traumatizing that she spent the next three decades crossing the street to avoid close contact with a dog, even a little one. Finally, though, it wasn’t any particular dog who changed her mind, it was her commitment to health. As a physician specializing in lifestyle medicine, Frates thought she had all the bases covered—diet, exercise, meditation. But when she took a health and longevity quiz to determine her “real” age (as opposed to her chronological one), she was surprised that one of the questions concerned dog ownership.

Intrigued by the implications, she began to review the existing literature, much of which has been summarized in this special report. She also purchased a Goldendoodle she named Reesee, from a breeder in West Virginia. “Everything has been different for me since then,” Frates says, adding that she and Reesee are regular running buddies. “When we go running, she is so happy and I’m happy because she’s happy. You just appreciate the world in a much different way.”

Frates believes that if something like the Harvard Health Report had been available years ago, she would have explored the joys of dog ownership much sooner. Now, she hopes that the report will encourage other non-dog people to reconsider their position. “We’re hoping to encourage people to take the leap of getting to know a dog,” she says. “And perhaps we’ll also be able to encourage more dog adoptions—that’s a focus that Lisa brought to the project.”

That’s because the nonprofit Angell Animal Medical Center, where Moses works, is part  MSPCA, the nation’s second oldest humane society, and has a very active adoption component. (Now that she realizes the situation for homeless dogs, Frates says she would adopt in the future.) Get Healthy, Get a Dog includes a section on “Adopting a Dog,” which provides information on determining the right breed for your home and suggestions on finding breed rescue groups and shelters. It also urges people to stay away from pet stores, where the dogs typically come from puppy mills.

Moses hopes readers will follow the report’s suggestions and reap the amazing benefits of dog ownership.

“Dogs are more important now than ever before,” she says. “Because people are living longer and so many live alone and don’t have kids. This is the moment for the human-animal bond.”

The report is available as a printed document, a PDF or both and can be purchased online at health.harvard.edu/staying-healthy/get-healthy-get-a-dog.