Reviews of Placebos for Pets? The Truth about Alternative Medicine for Animals

People have been writing some great reviews of Placebos for Pets, so I thought I’d share a few. If you liked it, please take a minute to add a review on Amazon or Goodreads and help spread the word. Thanks!

“I highly recommend this book. It’s well worth reading even if you don’t have a pet. It is well-written and easy to read… It’s a useful compendium of information on alternative medicine for animals, and it teaches readers how to figure out for themselves whether they can believe a new health claim. Since I know animals can’t read or speak for themselves, I will speak out for them: thank you, Brennen McKenzie, for this book, and for all your hard work and clear thinking!”
Harriet Hall, MD
Science-based Medicine Blog

“This is a great book for all pet owners, pet professionals, and others interested in animals who need help sifting through all the information on alternative veterinary medicine…His writing style is clear and down to earth, and he explains some very difficult concepts with grace… Reading this was a landmark life experience. Not only did I learn about a lot of specific alternative veterinary practices…I certainly added a few critical thinking tools to my toolbox!”
Eileen Anderson
Author, Remember Me?: Loving and Caring for a Dog with Canine Cognitive Dysfunction

“Just finished my copy this morning and couldn’t wait to post a review! This book is simply a must-read for veterinarians, veterinary team members, and pet owners of all shapes and sizes!

Beyond simply dismissing alternative medicine for animals, Dr. McKenzie provides a wealth of details and references in each chapter. From homeopathy to cold lasers to dietary supplements, his approach of “What is It?”, “Does It Work?” and “Is It Safe?” provides the reader with an easy to understand methodology of assessing the wide range of alternative veterinary medicine practices.

As someone who spends a great deal of time helping to educate and develop veterinary staff, this book will be an invaluable resource in helping me teach our teams about scientific method and sound reasoning.”
TFD, reader review

“A clear-eyed look at how science, which underpins veterinary medicine, can either be the logical basis for how it is practiced, or sometimes be the antithesis of certain veterinary practices. There’s irony in the book’s message, not least of which being why some veterinarians may so willingly suspend disbelief in adopting some of these techniques. We ought to inherently grasp that there really is no such thing as alternative medicine, only that medicine which works, and which has a basis in science, and that which some wish would work, but either doesn’t or is as yet unproven. What we offer to the public for compensation ought to be strictly from among the former. Placebos for Pets makes this all clear. Nicely written and referenced.”
Arnold Goldman, DVM, MPH

“This is a fabulous book. The author explains in laymans terms exactly what the issues are and a very easy to understand explanation of the scientific facts surrounding the more ‘popular’ placebos. I think that this book would be just as useful to help you explain to your pseudoscientific friends and relatives exactly what it is that they’re buying.”
Mike Fairburn, reader review

Posted in Presentations, Lectures, Publications & Interviews | 1 Comment

From SkeptVet TV- Pot for Pets?

My latest video from SkeptVet TV briefly reviews the evidence for cannabis-based health products for pets. You can find more detail here:

SkeptVet Blog posts on cannabis

Veterinary Practice News columns on cannabis (1, 2)

Posted in SkeptVet TV | 1 Comment

Evidence Update- Do PEMF Devices like the Assisi Loop Work?

Since the discovery of electricity and magnetism, these mysterious forces have been thought to have healing powers. Many fanciful electrical devices were promoted in the nineteenth and early twentieth century as cures for diverse ailments or general health tonics.1 More serious scientific research into the effects of electromagnetic fields on tissues and animals began in the 1930s, and by the 1980s there was sufficient evidence for some kinds of pulsed electromagnetic filed (PEMF) devices to be approved by the FDA for use in human patients.2

Since then, a large number of PEMF devices have been marketed for both human and veterinary medical use. The scientific evidence behind these devices, from in vitro and animal model studies to clinical trials, is complex and inconsistent. Pubmed lists about 50 systematic reviews covering nearly 200 clinical trials, and there well over 1,000 articles if one includes preclinical laboratory studies. PEMF devices use a variety of designs and treatment protocols for a wide range of medical conditions, so any generalizations about the efficacy of these devices are necessarily tenuous. However, because PEMF devices are aggressively marketed to veterinarians and animal owners, some assessment of the evidence behind them is necessary.

It’s been ten years since my first review of this subject, and there was little evidence to support claims for veterinary PEMF devices at the time. Though this is still the case, some new evidence is available.

Pre-clinical Evidence
There is a large scientific literature showing that electromagnetic fields have interesting and potentially significant biological effects on animal cells and tissues. PEMF devices can affect the levels of calcium and nitric oxide in tissues, which can influence extensive and complex pathways involved in metabolism, inflammation, pain transduction, tissue growth and repair, and many other biological activities. PEMF devices have also been shown to affect gene expression, vasomotor tone, and many other physiologic processes.2–5 These studies show the potential for clinically relevant benefits from PEMF treatment. 

Lab animal studies also show effects of PEMF treatment that may be useful to clinical patients, though there is great variation in the treatment used and the results. Some evidence suggests benefits in soft-tissue and bone healing, though not all of the research is positive.2,6–8

However, it is important to understand that such in vitro and animal model findings are not sufficient to justify clinical use. Many therapies, from pharmaceuticals to manual therapies to other high-tech treatments such as low-level laser, have demonstrable effects on tissues that often do not translate into meaningful clinical benefits for patients. Clinical trials are always necessary before making confident claims for any medical therapy.

Human Clinical Trial Evidence
Though there are hundreds of clinical studies in humans for PEMF in various indications, the results are mixed and difficult to interpret. For example, there are some studies showing meaningful improvements in post-operative pain in human patients undergoing breast augmentation surgery.9,10 However, systematic reviews of studies evaluating PEMF for pain associated with osteoarthritis of the knee are mixed, with some showing no effect,11 some inconclusive,12–15 and others suggesting some benefit.16 Strong generalizations about the efficacy of PEMF for pain aren’t justified based on a literature incorporating varied treatment protocols for different indications with mixed results.

The same inconsistency exists in studies of bone healing17–20 and other clinical uses in humans.21–23 There is evidence of benefits, but it is inconsistent, and the strength of this evidence is limited by heterogeneity in treatment protocols and indications as well as by methodological weaknesses in clinical trials. 

As always, clinical trial evidence for specific indications in veterinary patients is the most relevant type of evidence for veterinarians choosing which treatments to adopt. The clinical trial literature for PEMF is currently very sparse, but there are some studies we can evaluate.

Veterinary Clinical Trials
Though some encouraging case studies and uncontrolled studies have been published,24 there have been only a few controlled clinical trials of PEMF treatment in veterinary patients. 

A small pilot study randomly divided 16 dogs undergoing ovariohysterectomy into four groups- IV saline, IV saline and PEMF, IV morphine, and IV morphine and PEMF. For 6 hours after extubation, a variety of physiologic variables were measured, including heart and respiratory rates and blood pressure, and a validated pain scale was employed by a blinded observer. There were a couple of statistical differences in blood pressure at some time points, but no identifiable analgesic effect of PEMF. The small number of animals in each group likely made the study underpowered to detect all but the most dramatic effects.25

A 2018 study evaluated the use of a PEMF device in 16 dogs undergoing hemilaminectomy for naturally-occurring intervertebral disk disease (IVDD).26 Eight dogs were randomized to active or sham PEMF treatment and evaluated in terms of a primary outcome (gait) and numerous secondary outcomes involving neurologic status, function, and pain. There was no benefit detected in the primary outcome or in the majority of secondary outcomes. 

Placing responses and one measure of pain at the surgical site did appear improved in the PEMF group compared to the control. However, when multiple secondary outcomes are evaluated in a clinical study, it is common for some differences to appear by chance despite statistical efforts to control for this,27 and the authors state that these findings “should be interpreted with caution.”26

The most recent veterinary clinical trial also used IVDD patients as subjects.28 Fifty-three patients were randomly assigned to active or sham PEMF treatment and evaluated in the hospital and by owners at home for up to 6 weeks after surgery. There were no apparent benefits in terms of pain or function as assessed by owners or clinicians, though post-hoc power calculations indicated the study was not sufficiently powered to detect some of these differences. There were some small differences in long-term appearance of surgical wounds, though all wounds healed appropriately. Owners also gave slightly more pain medication to dogs in the control group than the PEMF group, though pain was not rated differently between the groups.

Bottom Line
Despite the fact that there has been interest in the potential medical applications of electricity for over 150 years, and serious scientific research investigating PEMF has been going on for over 50 years, there is surprisingly little robust evidence showing meaningful clinical benefits. We know a lot about the physiologic effects of PEMF, and preclinical research suggests a number of clinical applications. There is clinical trial evidence from humans showing potential benefits for bone and soft-tissue healing, pain reduction, and other uses, but this evidence is inconsistent and complicated by the use of many different devices and treatment protocols. PEMF devices are widely used, and this creates the impression that they have been solidly validated, but the reality is more ambiguous. 

There is also preclinical research in veterinary species showing physiological effects from PEMF devices and potential clinical applications. However, there are very few clinical trials of PEMF in actual patients. The studies that have been published have not found consistent and convincing evidence of clinically meaningful benefits. Many outcome measures have shown no effect of PEMF, though a few have shown effects that might be meaningful. If additional independent trials confirm such potential benefits, it may be possible to have confidence in some clinical uses of PEMF. For now, however, the marketing claims of PEMF manufacturers and the excitement of proponents far exceed the strength of the available scientific evidence.

It is also worth noting that most studies of PEMF devices in human and veterinary patients have found few, if any, adverse effects. While this is reassuring, it also calls into question the real potency of these devices. Medical treatments with important and dramatic benefits that have no meaningful side effects and extremely rare, and it is more common to find that the absence of adverse effects indicates the absence of any meaningful clinical effects at all.


1.        Kang L, Pedersen N. Quackery: A Brief History of the Worst Ways to Cure Everything. New York, NY: Workman Publishing, Inc.; 2017.

2.        Gaynor JS, Hagberg S, Gurfein BT. Veterinary applications of pulsed electromagnetic field therapy. Res Vet Sci. 2018;119:1-8. doi:10.1016/j.rvsc.2018.05.005

3.        Fini M, Giavaresi G, Carpi A, Nicolini A, Setti S, Giardino R. Effects of pulsed electromagnetic fields on articular hyaline cartilage: review of experimental and clinical studies. Biomed Pharmacother. 2005;59(7):388-394. doi:10.1016/j.biopha.2005.02.002

4.        Yuan J, Xin F, Jiang W. Underlying Signaling Pathways and Therapeutic Applications of Pulsed Electromagnetic Fields in Bone Repair. Cell Physiol Biochem. 2018;46(4):1581-1594. doi:10.1159/000489206

5.        Pilla AA. Nonthermal electromagnetic fields: From first messenger to therapeutic applications. Electromagn Biol Med. 2013;32(2):123-136. doi:10.3109/15368378.2013.776335

6.        Kwan R, Lu S, Choi H, Kloth L, Cheing G. Efficacy of Biophysical Energies on Healing of Diabetic Skin Wounds in Cell Studies and Animal Experimental Models: A Systematic Review. Int J Mol Sci. 2019;20(2):368. doi:10.3390/ijms20020368

7.        Crowe MJ, Sun Z-P, Battocletti JH, Macias MY, Pintar FA, Maiman DJ. Exposure to pulsed magnetic fields enhances motor recovery in cats after spinal cord injury. Spine (Phila Pa 1976). 2003;28(24):2660-2666. doi:10.1097/01.BRS.0000099385.46102.0D

8.        Inoue N, Ohnishi I, Chen D, Deitz LW, Schwardt JD, Chao EYS. Effect of pulsed electromagnetic fields (PEMF) on late-phase osteotomy gap healing in a canine tibial model. J Orthop Res. 2002;20(5):1106-1114. doi:10.1016/S0736-0266(02)00031-1

9.        Rawe IM, Lowenstein A, Barcelo CR, Genecov DG. Control of Postoperative Pain with a Wearable Continuously Operating Pulsed Radiofrequency Energy Device: A Preliminary Study. Aesthetic Plast Surg. 2012;36(2):458-463. doi:10.1007/s00266-011-9828-3

10.      Ae H, Pilla AA. Effects of Pulsed Electromagnetic Fields on Postoperative Pain: A Double-Blind Randomized Pilot Study in Breast Augmentation Patients. doi:10.1007/s00266-008-9169-z

11.      Cao L-Y, Jiang M-J, Yang S-P, Zhao L, Wang J-M. [Pulsed electromagnetic field therapy for the treatment of knee osteoarthritis: a systematic review]. Zhongguo Gu Shang. 2012;25(5):384-388. Accessed October 18, 2019.

12.      Chen L, Duan X, Xing F, et al. Effects of pulsed electromagnetic field therapy on pain, stiffness and physical function in patients with knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. J Rehabil Med. October 2019:0. doi:10.2340/16501977-2613

13.      Ryang We S, Koog YH, Jeong K-I, Wi H. Effects of pulsed electromagnetic field on knee osteoarthritis: a systematic review. Rheumatology. 2013;52(5):815-824. doi:10.1093/rheumatology/kes063

14.      Hulme JM, Welch V, de Bie R, Judd M, Tugwell P, Tugwell P. Electromagnetic fields for the treatment of osteoarthritis. In: Hulme JM, ed. Cochrane Database of Systematic Reviews. Chichester, UK: John Wiley & Sons, Ltd; 2002:CD003523. doi:10.1002/14651858.CD003523

15.      Negm A, Lorbergs A, MacIntyre NJ. Efficacy of low frequency pulsed subsensory threshold electrical stimulation vs placebo on pain and physical function in people with knee osteoarthritis: systematic review with meta-analysis. Osteoarthr Cartil. 2013;21(9):1281-1289. doi:10.1016/j.joca.2013.06.015

16.      Bjordal JM, Johnson MI, Lopes-Martins RA, Bogen B, Chow R, Ljunggren AE. Short-term efficacy of physical interventions in osteoarthritic knee pain. A systematic review and meta-analysis of randomised placebo-controlled trials. BMC Musculoskelet Disord. 2007;8(1):51. doi:10.1186/1471-2474-8-51

17.      Griffin XL, Costa ML, Parsons N, Smith N. Electromagnetic field stimulation for treating delayed union or non-union of long bone fractures in adults. Cochrane Database Syst Rev. April 2011. doi:10.1002/14651858.CD008471.pub2

18.      Al-Jabri T, Tan JYQ, Tong GY, et al. The role of electrical stimulation in the management of avascular necrosis of the femoral head in adults: a systematic review. BMC Musculoskelet Disord. 2017;18(1):319. doi:10.1186/s12891-017-1663-5

19.      Walker NA, Denegar CR, Preische J. Low-intensity pulsed ultrasound and pulsed electromagnetic field in the treatment of tibial fractures: a systematic review. J Athl Train. 42(4):530-535. Accessed October 18, 2019.

20.      Hannemann PFW, Mommers EHH, Schots JPM, Brink PRG, Poeze M. The effects of low-intensity pulsed ultrasound and pulsed electromagnetic fields bone growth stimulation in acute fractures: a systematic review and meta-analysis of randomized controlled trials. Arch Orthop Trauma Surg. 2014;134(8):1093-1106. doi:10.1007/s00402-014-2014-8

21.      Page MJ, Green S, Kramer S, Johnston R V, McBain B, Buchbinder R. Electrotherapy modalities for adhesive capsulitis (frozen shoulder). Cochrane Database Syst Rev. 2014;(10):CD011324. doi:10.1002/14651858.CD011324

22.      Page MJ, Green S, Mrocki MA, et al. Electrotherapy modalities for rotator cuff disease. Cochrane Database Syst Rev. 2016;(6):CD012225. doi:10.1002/14651858.CD012225

23.      Hug K, Röösli M. Therapeutic effects of whole-body devices applying pulsed electromagnetic fields (PEMF): A systematic literature review. Bioelectromagnetics. 2012;33(2):95-105. doi:10.1002/bem.20703

24.      Gaynor JS, Hagberg S, Gurfein BT. Veterinary applications of pulsed electromagnetic field therapy. Res Vet Sci. 2018;119:1-8. doi:10.1016/j.rvsc.2018.05.005

25.      Shafford HL, Hellyer PW, Crump KT, Wagner AE, Mama KR, Gaynor JS. Use of a pulsed electromagnetic field for treatment of post–operative pain in dogs: a pilot study. Vet Anaesth Analg. 2002;29(1):43-48. doi:10.1046/j.1467-2987.2001.00072.x

26.      Zidan N, Fenn J, Griffith E, et al. The Effect of Electromagnetic Fields on Post-Operative Pain and Locomotor Recovery in Dogs with Acute, Severe Thoracolumbar Intervertebral Disc Extrusion: A Randomized Placebo-Controlled, Prospective Clinical Trial. J Neurotrauma. 2018;35(15):1726-1736. doi:10.1089/neu.2017.5485

27.      Heneghan C, Goldacre B, Mahtani KR. Why clinical trial outcomes fail to translate into benefits for patients. Trials. 2017;18(1):122. doi:10.1186/s13063-017-1870-2

28.      Alvarez LX, McCue J, Lam NK, Askin G, Fox PR. Effect of Targeted Pulsed Electromagnetic Field Therapy on Canine Postoperative Hemilaminectomy: A Double-Blind, Randomized, Placebo-Controlled Clinical Trial. J Am Anim Hosp Assoc. 2019;55(2):83-91. doi:10.5326/JAAHA-MS-6798

Posted in Science-Based Veterinary Medicine | Leave a comment

From SkeptVet TV- Raw Diets for Pets

Here is my latest video from SkeptVet TV, reviewing briefly the subject of raw diets for dogs and cats. You can find more information here on the blog, or in my book, Placebos for Pets? The Truth About Alternative Medicine for Animals.

Posted in SkeptVet TV | 6 Comments

Veterinary Homeopathy: Why Are We Still Talking about This?

In two years of writing my Veterinary Practice News column about evidence-based medicine, I have largely managed to avoid the subject of homeopathy. It is the classic example of a medical practice developed before a scientific understanding of the basic mechanisms of health and disease existed, and it has remained true to 18th-century principles despite all of the subsequent advances in medical knowledge. Controversial from its beginnings,1 homeopathy has long been employed by only a few healthcare professionals, and surveys show only a tiny minority of citizens in most developed countries have used homeopathic treatment.2–4

It would seem safe, then, to dismiss and ignore this relic of pre-scientific medicine. However, homeopathy has managed to retain a small following in both human and veterinary medicine, and its proponents are sometimes visible and influential out of proportion to their numbers. Clients often ask me about using homeopathic remedies they have heard about from friends or online, often from veterinarians who support the practice. 

What is more, misleading information about homeopathy continues to be presented at major veterinary continuing education conferences and to appear in niche alternative veterinary medicine journals, which helps to create doubt about the scientific evidence concerning this practice. Attempts by regulators and professional organizations to discourage the use of homeopathy have had mixed results, thanks to vigorous lobbying against the scientific consensus by a vocal minority. Therefore, a brief evidence-based overview of veterinary homeopathy may still be useful to pet owners and veterinary professionals.

Basic Principles
The first rule of homeopathy is that something which causes certain symptoms in a healthy person is the best treatment for those symptoms in someone who is sick, a principle known as the Law of Similars.5 This clearly reflects a metaphorical approach to disease which, in modern medical science, has been replaced by specific pathophysiologic explanations derived from scientific research. Apart from this flaw, however, the Law of Similars has the obvious problem that if you give an ill patient something which creates symptoms of illness in normal individuals, you will often make them worse! 

Samuel Haahnemann, the inventor of homeopathy, discovered this problem through trial and error with his own patients.5,6 Instead of recognizing that his basic principle was flawed, however, he took the approach of greatly diluting his remedies, which reduced their ill effects. In the absence of the harm done by the traditional remedies used at the time, many of which were toxic to some degree, some of Hahnemann’s patients recovered after taking his diluted preparations. Since the only evidence available at the time for assessing efficacy was anecdote and subjective experience, this was interpreted as successful treatment.

This “success” led Hahnemanns to the second foundational principle of homeopathy, the principle of Potentization by Dilution and Succussion. This principle states that homeopathic medicines become more potent the less active ingredient they contain. (Succussion refers to shaking the remedies, since Hahnemann apparently also believed that the agitation his medicines received as he travelled on horseback to see his patients somehow increased their curative power.)5,6

Finally, homeopathy relies on a complex process for individualizing the use of homeopathic preparations by evaluating the physical and mental experiences of patients and comparing them with experiences reported by healthy individuals testing specific homeopathic remedies. The details of this process are too involved to summarize here, but they involve a purely subjective and anecdotal process that has not been, and probably cannot be, validated through controlled scientific research.

The Scientific Evidence
Despite the inherent implausibility of these concepts and the general incompatibility of homeopathic theory with established principles of physiology, chemistry, pharmacology, and other modern disciplines in medical science, there has been a lot of pre-clinical and clinical research on homeopathic remedies and treatments. The majority of this has been published in journals devoted exclusively to homeopathy of other alternative therapies, and there is often a lack of proper methodological controls and significant risk of bias in these publications. Numerous systematic reviews of homeopathy in human medicine have been published, and the majority show no evidence of real or clinically meaningful effects beyond that of placebos.2,7-35 When sufficient studies are conducted and published by committed advocates for any practice, bias will inevitably lead to some apparently positive results, but such results have not been replicated or validated by consistent, unbiased investigation.

The veterinary literature concerning homeopathy is, as always, sparser than that in human medicine, but the same general assessment applies. Despite some ostensibly positive findings in low-quality studies with high residual bias risk, the preponderance of the evidence shows no real or replicable effects. Even dedicated proponents of homeopathy are unable to find convincing high-quality research evidence for the practice when they apply accepted methods for evaluating the literature.36–42

Evidence-based medicine is always about a flexible and probabilistic understanding, and absolute, immutable conclusions are anathema to the core principles of this approach. However, evaluating homeopathy at every level, from biologic plausibility to pre-clinical and in vitro research to clinical trials leads to as confident a conclusion as science can ever muster, which is that the practice has no benefits.

The Future of Veterinary Homeopathy
It seems clear, given this scientific conclusion, that homeopathy can have no legitimate role in modern veterinary medicine. It is unethical to offer clients ineffective remedies, and even when the treatments themselves may do no harm they can mislead clients and discourage the use of truly effective treatments. 

A number of regulators and professional organizations have recognized this and taken action. The Federal Trade Commission and the Food and Drug Administration have recently issued statements warning the public that claims for the safety and efficacy of homeopathy are not supported by science. In the veterinary field, the Australian Veterinary Association, British Veterinary Association, and the Royal College of Veterinary Surgeons all have clear policy statements acknowledging homeopathy as ineffective and discouraging its use. Numerous specialty colleges in the U.S. and abroad have issued similar statements. The American Veterinary Medical Association, unfortunately, declined to adopt a similar policy in 2014 despite a finding from its own Council on Research that, “there is no clinical evidence to support the use of homeopathic remedies for treatment or prevention of diseases in domestic animals.”43

Political and economic considerations, as well as vehement advocacy and misleading information from proponents of homeopathy, have kept the method alive despite the clear scientific evidence against it. Hopefully, the current trend towards accepting the verdict of science will continue, and homeopathy will continue to decline and eventually disappear from veterinary journals and continuing education. Undoubtedly, some practitioners and clients will always choose anecdote and wishful thinking over evidence, but as members of a scientific medical professional, we have a responsibility to provide effective care for our patients and honest, accurate information for our clients. Meeting this core ethical responsibility leaves no place for equivocation or failing to clearly discourage the use of homeopathy.


1.        Holmes OW. Homeopathy and Its Kindred Delusions: Two Lectures Delivered before the Boston Society for the Diffusion of Useful Knowledge. Boston, MA: William D. Ticknor; 1842.

2.        Banerjee K, Mathie RT, Costelloe C, Howick J. Homeopathy for Allergic Rhinitis: A Systematic Review. J Altern Complement Med. 2017;23(6):426-444. doi:10.1089/acm.2016.0310

3.        Alexander H. Parents guilty of manslaughter over daughter’s eczema death. Sydney Morning Herald. Published June 5, 2009.

4.        Su D, Li L. Trends in the use of complementary and alternative medicine in the United States: 2002-2007. J Health Care Poor Underserved. 2011;22(1):296-310. doi:10.1353/hpu.2011.0002

5.        Kunzli J, Naude A, Pendleton P Tarcher PJ. Organon of medicin Samuel Hahnemann the first integral english translation of the definitive sixth edition of the original work on homoeopathic medicine a new translation. Translation of Organon Der Rationellen Heilkunde. Includes Index. 1. Homoeopathy 2. Title Design by Thom Dower manufactured in the United States of America first edition.; 1982. Accessed November 11, 2018.

6.        Bradford TL. The Life and Letters of Dr. Samuel Hahnemann. Philadelphia, PA: Boericke & Tafel; 1895.

7.        Barnes J, Resch KL, Ernst E. Homeopathy for postoperative ileus? A meta-analysis. J Clin Gastroenterol. 1997;25(4):628-633. Accessed November 12, 2018.

8.        Ernst E, Barnes J. Are homoeopathic remedies effective for delayed-onset muscle soreness: a systematic review of placebo-controlled trials. 1998. Accessed November 12, 2018.

9.        Ernst E, Pittler MH. Re-analysis of previous meta-analysis of clinical trials of homeopathy. J Clin Epidemiol. 2000;53(11):1188. Accessed November 12, 2018.

10.      Ernst E, Pittler MH. Efficacy of homeopathic arnica: a systematic review of placebo-controlled clinical trials. Arch Surg. 1998;133(11):1187-1190. Accessed November 12, 2018.

11.      Ernst E (Edzard). Homeopathy?: The Undiluted Facts?: Including a Comprehensive A-Z Lexicon. Cham?: Springer International Publishing?:;Imprint: Springer,; 2016.

12.      Ernst E. Homeopathy – The Undiluted Facts. Cham: Springer International Publishing; 2016. doi:10.1007/978-3-319-43592-3

13.      Fisher P, Dantas F. Homeopathic pathogenetic trials of Acidum malicum and Acidum ascorbicum. Br Homeopath J. 2001;90(3):118-125. doi:10.1038/sj/bhj/5800476

14.      Goodyear K, Lewith G, Low JL. Randomized double-blind placebo-controlled trial of homoeopathic “proving” for Belladonna C30. J R Soc Med. 1998;91(11):579-582. Accessed November 12, 2018.

15.      Hirst SJ, Hayes NA, Burridge J, Pearce FL, Foreman JC. Human basophil degranulation is not triggered by very dilute antiserum against human IgE. Nature. 1993;366(6455):525-527. doi:10.1038/366525a0

16.      Jonas WB, Linde K, Ramirez G. Homeopathy and rheumatic disease. Rheum Dis Clin North Am. 2000;26(1):117-123, x. Accessed November 12, 2018.

17.      Linde K, Clausius N, Ramirez G, et al. Are the clinical effects of homeopathy placebo effects? A meta-analysis of placebo-controlled trials. Lancet (London, England). 1997;350(9081):834-843. Accessed November 12, 2018.

18.      Becker-Witt C, Weißhuhn TER, Lüdtke R, Willich SN. Quality Assessment of Physical Research in Homeopathy. J Altern Complement Med. 2003;9(1):113-132. doi:10.1089/107555303321222991

19.      Linde K, Melchart D. Randomized controlled trials of individualized homeopathy: a state-of-the-art review. Altern Complement Ther. 1998;4(6):371-373. doi:10.1089/act.1998.4.371

20.      Linde K, Scholz M, Ramirez G, Clausius N, Melchart D, Jonas WB. Impact of study quality on outcome in placebo-controlled trials of homeopathy. J Clin Epidemiol. 1999;52(7):631-636. Accessed November 12, 2018.

21.      Long L, Ernst E. Homeopathic remedies for the treatment of osteoarthritis: a systematic review. Br Homeopath J. 2001;90(1):37-43. Accessed November 12, 2018.

22.      McCarney RW, Linde K, Lasserson TJ. Homeopathy for chronic asthma. Cochrane Database Syst Rev. 2004;(1):CD000353. doi:10.1002/14651858.CD000353.pub2

23.      Moffett JR, Arun P, Namboodiri MAA. Laboratory research in homeopathy: con. Integr Cancer Ther. 2006;5(4):333-342. doi:10.1177/1534735406294795

24.      Ovelgönne JH, Bol AW, Hop WC, van Wijk R. Mechanical agitation of very dilute antiserum against IgE has no effect on basophil staining properties. Experientia. 1992;48(5):504-508. Accessed November 12, 2018.

25.      Shang A, Huwiler-Müntener K, Nartey L, et al. Are the clinical effects of homoeopathy placebo effects? Comparative study of placebo-controlled trials of homoeopathy and allopathy. Lancet (London, England). 2005;366(9487):726-732. doi:10.1016/S0140-6736(05)67177-2

26.      Vickers AJ. Independent replication of pre-clinical research in homeopathy: a systematic review. Forsch Komplementarmed. 1999;6(6):311-320. doi:10.1159/000021286

27.      Vickers A, McCarney R, Fisher P, van Haselen R. Can homeopaths detect homeopathic medicines? A pilot study for a randomised, double-blind, placebo controlled investigation of the proving hypothesis. Br Homeopath J. 2001;90(3):126-130. doi:10.1038/sj/bhj/5800475

28.      Walach H, Köster H, Hennig T, Haag G. The effects of homeopathic belladonna 30CH in healthy volunteers — a randomized, double-blind experiment. J Psychosom Res. 2001;50(3):155-160. Accessed November 12, 2018.

29.      Cucherat M, Haugh MC, Gooch M, Boissel JP. Evidence of clinical efficacy of homeopathy. A meta-analysis of clinical trials. HMRAG. Homeopathic Medicines Research Advisory Group. Eur J Clin Pharmacol. 2000;56(1):27-33. Accessed November 12, 2018.

30.      Dantas F, Fisher P, Walach H, et al. A systematic review of the quality of homeopathic pathogenetic trials published from 1945 to 1995. Homeopathy. 2007;96(1):4-16. doi:10.1016/j.homp.2006.11.005

31.      Endler P, Thieves K, Reich C, et al. Repetitions of fundamental research models for homeopathically prepared dilutions beyond 10(-23): a bibliometric study. Homeopathy. 2010;99(1):25-36. doi:10.1016/j.homp.2009.11.008

32.      Ennis M. Basophil models of homeopathy: a sceptical view. Homeopathy. 2010;99(1):51-56. doi:10.1016/j.homp.2009.11.005

33.      Ernst E. Homeopathic prophylaxis of headaches and migraine? A systematic review. J Pain Symptom Manage. 1999;18(5):353-357. Accessed November 12, 2018.

34.      Ernst E. A systematic review of systematic reviews of homeopathy. Br J Clin Pharmacol. 2002;54(6):577-582. Accessed November 12, 2018.

35.      Ernst E. Classical homoeopathy versus conventional treatments: a systematic review. 1999. Accessed November 12, 2018.

36.      Doehring C, Sundrum A. Efficacy of homeopathy in livestock according to peer-reviewed publications from 1981 to 2014. Vet Rec. 2016;179(24):628. doi:10.1136/vr.103779

37.      Mathie RT, Clausen J. Veterinary homeopathy: Systematic review of medical conditions studied by randomised trials controlled by other than placebo. BMC Vet Res. 2015;11(1):236. doi:10.1186/s12917-015-0542-2

38.      Mathie RT. Controlled clinical studies of homeopathy. Homeopathy. 2015;104(4):328-332. doi:10.1016/j.homp.2015.05.003

39.      Mathie RT, Clausen J. Veterinary homeopathy: systematic review of medical conditions studied by randomised placebo-controlled trials. 2014;175(15). doi:10.1136/vr.101767

40.      Mathie RT, Clausen J. Veterinary homeopathy: meta-analysis of randomised placebo-controlled trials. Homeopathy. 2015;104(1):3-8. doi:10.1016/j.homp.2014.11.001

41.      McKenzie BA. The Evidence for Homeopathy- A Close Look.; 2013. Accessed September 13, 2019.

42.      McKenzie BA. White Paper: The Case Against Homeopathy.; 2013. Accessed September 13, 2019.

43.      Burns K. House of Delegates to deliberate again on homeopathy, acupuncturists. JAVMA News. Published 2013. Accessed September 13, 2019.

Posted in Homeopathy | 5 Comments

Calming Care Probiotic for Anxiety in Dogs

I first wrote about the subject of probiotics in 2009, and I have added quite a few articles on the subject since (12345,67891011). Overall, the evidence has been mixed but pretty poor for most conditions. The best evidence suggests some possible benefit for acute gastrointestinal problems such as diarrhea, but the veterinary probiotic literature is sparse and poor quality, with significant risk of bias, particularly given that almost all studies are funded by companies selling probiotic products. There is also evidence that the quality of probiotic products available for dogs and cats is poor.

The most recent product to enter this area is a bit different from others in that it is explicitly intended to treat behavioral problems, rather than the more typical gastrointestinal disease. Purina Calming Care is promoted “to help dogs maintain calm behavior. It supports dogs with anxious behaviors and helps them cope with external stressors like separation, unfamiliar visitors, novel sounds or changes in routine and location. It also helps dogs maintain positive cardiac activity during stressful events, promoting a positive emotional state.”

The idea that a probiotic might help with diarrhea of chronic GI disease is fairly intuitive, but the claim that feeding specific microorganisms can influence behavior seems a bit more farfetched. However, there turns out to be quite a bit of evidence in lab animals and humans that the ecology of the GI tract does have significant effects on the chemistry of the central nervous system, and the mood and behavior that results.1,2 There are also a number of reviews of experimental studies in humans specifically evaluating probiotics as treatments for anxiety and depression, and while there are plenty of limitations and lots of inconsistency, the evidence is actually fairly encouraging.2–7

Of course, the devil is in the details, and even in humans it is difficult to say with confidence that any given probiotic will help any specific patient. Though there is some positive clinical research, the studies use different probiotics in different forms for different populations with different problems, and this heterogeneity makes generalizations about the value of probiotics for mood disorders unreliable. In veterinary medicine, the situation is considerably worse since the evidence is far less robust.

There are no fully peer-reviewed studies of probiotics for behavioral problems in dogs or cats. The best we have is an abstract of a Purina study evaluating their Calming Care product in dogs. Twenty-four dogs described as “anxious” (no more formal diagnosis was given) were tested with and without the product over six-week periods. Purportedly blinded observations of behavior and measurements of objective markers such as heart rate and cortisol levels in saliva all showed changes during the period on the probiotic that would suggest a beneficial effect. However, the information about how the study was conducted is too limited to effectively appraise its quality, and of course it is an in-house study run by the company to provide marketing material for their own product, so potential bias is certainly a concern.

As I have pointed out previously, the risks of probiotics appear to be low, though some cases of direct injury and instances of transmission of genes for antibiotic resistance passed from probiotic organisms to pathogenic bacteria have been reported. In the face of encouraging but incomplete lab animal and human evidence and virtually no research in veterinary patients, it is not unreasonable to try a product like Calming Care for dogs with anxiety-related problems, but we can have little confidence in its effects.


1.        McKean J, Naug H, Nikbakht E, Amiet B, Colson N. Probiotics and Subclinical Psychological Symptoms in Healthy Participants: A Systematic Review and Meta-Analysis. J Altern Complement Med. 2017;23(4):249-258. doi:10.1089/acm.2016.0023

2.        Wang H, Lee I-S, Braun C, Enck P. Effect of Probiotics on Central Nervous System Functions in Animals and Humans: A Systematic Review. J Neurogastroenterol Motil. 2016;22(4):589-605. doi:10.5056/jnm16018

3.        Nikolova V, Zaidi SY, Young AH, Cleare AJ, Stone JM. Gut feeling: randomized controlled trials of probiotics for the treatment of clinical depression: Systematic review and meta-analysis. Ther Adv Psychopharmacol. 2019;9:204512531985996. doi:10.1177/2045125319859963

4.        Liu RT, Walsh RFL, Sheehan AE. Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials. Neurosci Biobehav Rev. 2019;102:13-23. doi:10.1016/j.neubiorev.2019.03.023

5.        Wallace CJK, Milev R. The effects of probiotics on depressive symptoms in humans: a systematic review. Ann Gen Psychiatry. 2017;16(1):14. doi:10.1186/s12991-017-0138-2

6.        Pirbaglou M, Katz J, de Souza RJ, Stearns JC, Motamed M, Ritvo P. Probiotic supplementation can positively affect anxiety and depressive symptoms: a systematic review of randomized controlled trials. Nutr Res. 2016;36(9):889-898. doi:10.1016/j.nutres.2016.06.009

7.        Huang R, Wang K, Hu J. Effect of Probiotics on Depression: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2016;8(8):483. doi:10.3390/nu8080483

Posted in Herbs and Supplements | 2 Comments

From The Atlantic- An article discussing placebo effects in veterinary patients

A Crucial Blind Spot in Veterinary Medicine

While the placebo effect is a well-established phenomenon in human patients, it’s an underappreciated one in veterinary medicine. And the particular way it plays out in veterinary care highlights how unconscious cognitive biases can mislead humans when we care for other species. Even when pet owners are determined to provide first-rate care for the animals they love, these blind spots can undermine their best efforts. “The stories that we tell about our pets often aren’t really reflecting what’s happening to their bodies,” says Brennen McKenzie, a veterinarian and the author of SkeptVet, a blog dedicated to evidence-based veterinary medicine.

Posted in Presentations, Lectures, Publications & Interviews | 1 Comment

Dr. Marty Goldstein’s Nature’s Feast Raw Diet: A Look at the Infomercial

A client recently asked one of my colleagues for an opinion on an infomercial by Dr. Marty Goldstein for his new commercial raw cat food, Nature’s Feast. There was little new or surprising in this video, but since Dr. Goldstein has a lot of prominence in the media, cat owners may run across this video and be inclined to believe the claims made in it, so I felt it worthwhile to provide some context.

Who is Dr. Marty Goldstein?
I have written a bit about him before as a contributor to the propaganda film The Truth About Pet Cancer, which I havepreviously critiqued in detail

Dr. Goldstein is another celebrity participant, a veterinarian to the stars. He is also a strong advocate of the bait-and-switch known as “integrative medicine.” This means he will sometimes use science-based treatments, but then often gives the credit for any improvement to homeopathy, acupuncture, raw diets, herbs, and other alternative treatments he also employs.

Dr. Goldstein, much like Jean Dodds, is one of those alternative practitioners who is so nice and caring and respected (at least by celebrity clients and alternative medicine advocates) that it is considered almost taboo to point out that much of what he sells is unproven at best and, in some cases, complete nonsense. His use of homeopathy clearly demonstrates his lack of concern for a science-based approach to medicine, and most of the claims he makes about nutrition are unproven at best or clearly wrong at worst.

He justifies his claims almost entirely with personal anecdotes and beliefs, not with any objective scientific evidence. I have discussed the unreliability of anecdotes many times, as well as many of the flimsy arguments he uses in this infomercial, such as the Appeal to Nature Fallacy, so I will only address them briefly here. Dr. Goldstein is clearly convinced that his personal experience and beliefs are sufficient evidence for rejecting the conclusions of scientific research and nutrition experts, and that alone makes any claim he makes suspect.

The most egregious story he tells is about a dog named Kaiser. Dr. Goldstein convinced this dog’s owners to switch form a commercial to a homemade diet. For a couple of weeks after that, supposedly anybody who touched the dog developed a skin rash, and then the dog’s hair all fell out. Rather than seeing this as a problem or a sign of serious illness, Dr. Goldstein interpreted it as a sign the dog was “detoxing,” releasing harmful chemicals through its skin due to the diet change. Such a dangerously bizarre interpretation of potentially serious symptoms does not suggest a rational or reliable medical judgment.

As for the specific claims he makes in his infomercial, here are a few of the most important.

Grains are Bad for Cats
Grains are popular villains in alternative narratives about nutrition these days. The ratio of the three macronutrients—carbohydrates, fat, and protein— are a key element in the formulation of pet diets. None of these are inherently “good” or “bad,” and while the precise balance among them does have health implications, especially in pets with specific medical conditions, such as diabetes or kidney disease, the idea that commercial diets generally contain “too much sugar” or other carbohydrates and that this causes disease is simply not consistent with the evidence. 

Unlike humans, dogs and cats can live with little or no carbohydrate in their diet. However, they can also use this class of macronutrient perfectly well as a source of calories. Some non-digestible carbohydrates (often known as “fiber”) can have beneficial effects on the microbes that live in our pets’ guts, which can influence health, as well as on weight, stool consistency, and other aspects of health. Demonizing an entire class of nutrient is not rational or justified.

As far as the claims that dietary carbohydrates of grains lead to cancer or other disease in pets, these are pure speculation. There are only a few studies looking at diet and cancer risk in dogs and cats, and most of these rely owner recollections for data about diet, which has proven a very unreliable approach in people. There are no studies at all showing restricting dietary carbohydrates reduces the risk of developing cancer in dogs and cats.

There are lab animal studies and epidemiologic research in humans which suggest possible relationships between carbohydrates in the diet and cancer. There are interesting features of the metabolism of cancer cells that suggest diet might have some influence on cancer progression and response to treatment. But there is no real-world, clinical trial evidence that supports the claim that dietary carbohydrates cause cancer in pets or that lower carbs will prevent or help treat cancer. 

Carbohydrates are often seen as particularly dangerous to cats, who are truly obligate carnivores and so would naturally eat a high-fat/high-protein diet with few carbohydrates or grains in it, other than those found in the digestive system of herbivorous prey animals. However, research has demonstrated that cats can make use of carbohydrates in food as an energy source, and that these are not a significant risk factor for diabetes or other diseases often blamed on too much carbohydrate in commercial cat food. 

Perhaps the pet food ingredients most reviled in criticism of commercial pet foods are corn and wheat. The obsession in popular human nutrition lore about gluten has certainly contributed to this. However, many of the fears about gluten, in human and animal health, are unfounded.  People with celiac disease can have negative health effects associated with eating gluten, and there are documented genetic cases of gluten sensitivity in a couple of dog breeds.

However, just as most people are not harmed by eating gluten, there is no evidence that this is a risk factor for disease in dogs and cats. Abandoning wheat as a macronutrient source because of such fears simply leads to the substitution of other sources, and there is no guarantee these are safer or healthier. There is even some evidence that avoiding gluten can cause problems in people who do not have celiac disease. 

I have also heard advocates of alternative diets talk about “the menacing power of corn” as if it were inherently poisonous. This is simply silly, and it ignores decades of nutrition research showing the contrary. Like every other food ingredient, corn is not inherently good or bad. It can contribute calories, protein, and essential fats to the diet, and it can be a safe ingredient in a balanced diet for both dogs and cats. It is obviously not appropriate as the sole food source for our pets, but no one is suggesting we use it that way, and claims that pet foods are “mostly corn” are demonstrably untrue.

Artificial Preservatives
This is a claim I have addressed repeatedly in previous articles. A variety of synthetic antioxidants have been used in pet foods over the years to prevent spoilage, and the risk of food poisoning that goes with it. These substances are sometimes feared as potential causes of cancer based on studies in rats or mice where enormous quantities are fed to the animals to evaluate potential risks. However, extensive research on these substances as they are actually used as preservatives in human and pet foods has failed to find such risks in the real world. This is another example of the dangers in putting too much stock in the predictive value of laboratory studies. 

Some companies have moved to using “natural” preservatives, such as Vitamin E, and this is what Dr. Goldstein recommends. These may be less effective, and there is no clear evidence that they are safer, but the pet food industry is often forced to respond to the fears of consumers, stoked by claims from proponents of alternative diets, regardless of the evidence for or against the concerns. 

Raw Food is Healthier than Cooked Food
This is another claim I have responded to many, many times, and there is still no evidence to support it and plenty of evidence against it. As with most alternative health practices, there are a variety of theories and specific beliefs behind raw feeding, but there are several consistent themes that most proponents of the approach adhere to and use in promoting it.

The first is the claim that commercial diets are nutritionally inappropriate and unhealthy. All of the criticisms of conventional diets I have addressed elsewhere on the blog (e.g. 12) and in detail in my book, are put to the service of convincing people raw diets are a better choice. While commercial pet foods are not perfect or without risks, the evidence clearly shows they are healthy and nutritionally appropriate for the vast majority of dogs and cats, and millions of pets live long and healthy lives eating these foods. 

The other main theoretical argument for raw diets is our old friend the Appeal to Nature Fallacy. The argument runs something like this: Cats are carnivores and they, or their ancestors, ate whole prey in the wild. Evolution has adapted carnivores to this diet, so it is the optimal diet for them. Our pet cats are essentially the same in their nutritional needs as their wild cousins or ancestors, so a diet as much like raw, whole prey as possible is the healthiest diet for them.

Cats have generally been altered far less by their association with humans than dogs. While dogs are most properly classified as omnivores, or facultative carnivores, cats are true carnivores in terms of their anatomy and physiology. Domestic cats do likely have nutritional needs very similar to wild felines. So does this mean they are better off if fed a raw diet?

Well, the Appeal to Nature Fallacy is a fallacy precisely because what happens in nature doesn’t predict what is good or bad in terms of health. The diet wild animals eat is not the perfect diet designed for their long-term health and happiness, it is simply the diet that is available to them. Evolution works by an impersonal process in which animals do their best to meet their physical needs with what is available in their environment and then reproduce. The individuals who are best at meeting these needs leave more offspring and genes behind, and over time the population comes to be more like the more successful individuals because their genes become more common. Species and their environments are always interacting and changing, and there is never an ideal moment in which a species is optimally suited for its environment and every individual is perfectly happy and healthy.

Animals typically live longer, healthier lives in captivity compared to their wild relatives. Wild carnivores frequently suffer from malnutrition, often starving when they can’t catch sufficient prey to meet their calorie and other needs. They also suffer from parasites, infectious diseases, and injuries from catching and consuming whole prey, and they endure this either suffering or die from it. This is not a perfect, blissful state of nature our pets should aspire to, it is simply the way things are in nature. 

Humans no longer live like our stone age ancestors, and we have altered our homes, our clothes, and our diets significantly from that “natural” state. As a result, we suffer less and live longer, healthier lives because of “artificial” practices such as washing and cooking and refrigerating our feed and providing ourselves with nutrients that were once hard to come by. The reduction of scurvy and rickets in modern children compared to those of our ancestors is a good thing, and similarly the reduction in parasites and malnutrition in our pets thanks to “artificial” feeding practices is a positive change. 

Raw feeding is often associated with other alternative medicine beliefs and practices. Surveys show that pet owners who feed raw diets are less likely to trust nutrition advice from veterinarians and are also less likely to adhere to other recommendations, such vaccination and parasite prevention, than owners who feed traditional commercial diets. Veterinarians who promote raw feeding and condemn conventional diets are also often suspicious of vaccines and other science-based medical therapies and frequently advocate alternative medical practices. It is not surprising, then, that theories and beliefs which underlie other alternative practices are also found in arguments for raw diets. 

None of these theoretical justifications for a raw diet, that commercial diets are unhealthy, that our pets are essentially identical to wild carnivores, that a diet as close as possible to that they would eat in nature is best for their health, or that raw food contains some intangible but essential spiritual nutrient lacking in cooked food, hold up very well to logical scrutiny. So is there any actual evidence that raw diets have health benefits?

A few small and short-term studies have been done in which dogs and cats have been fed raw foods. These show some interesting changes in the bacteria living in the guts of these subjects, in stool, and in metabolism and other variables. However, these studies simply show that some small things change when the diet is changed, not that raw diets have meaningful health effects or that whatever effects are seen are due primarily to the lack of cooking. One study has suggested some possible benefits for dental health in dogs fed a raw diet, but another study identified dental disease and broken teeth caused by such diets.

Overall, there is no convincing research evidence to support the theories and claims for why raw diets should be better for our pets than cooked homemade or conventional commercial diets. 

Unlike the benefits of raw diets, which are theoretical and unproven, the risks are well documented. Commercial raw diets which meet industry standards are likely to be nutritionally complete, but many raw advocates feed home-prepared diets, and just like other homemade foods, these diets are frequently nutritionally unbalanced and incomplete. There is even one report of a whole-prey diet (whole ground rabbit) which was studied in cats as a representative of a “natural” diet but which turned out to generate severe heart disease due to taurine deficiency in the cats eating it. So much for “natural” meaning “healthy!” 

The most significant risk of raw diets is from food-borne infectious disease. Numerous studies have shown raw diets to be frequently contaminated with potentially dangerous bacteria. While such pathogens can contaminate cooked diets as well, the risk is significantly higher for raw foods. Other studies have shown that animals eating these diets often shed these dangerous organisms in their feces, which exposes humans and other animals to the risk of infection.

Most importantly, serious illness and death in cats and dogs, and in their owners, have been caused by pathogens found in raw pet diets. While the number of confirmed cases of pets and humans suffering or dying from food-borne illness caused by raw diets is small, this is a very serious health hazard. While healthy adult pets may be able to resist these organisms to some extent, there is no absolute immunity in dogs and cats to food-borne illness. Very young, old, and sick animals, and their human caregivers, are at even higher risk. 

Dr. Goldstein claims that the freeze-drying of his pet food “completely eliminates” this risk, but that is just his opinion based on anecdote, and this is disputed by both veterinary nutritionists and veterinary infectious disease specialists

He also claims that cooking destroys nutrients in food, including taurine, which is essential for normal heart health in cats. He claims that the vitamin supplementation done to compensate for this is not effective, but there is ample evidence this is untrue and that supplementation prevents any micronutrient deficiencies in commercial diets. In fact, his claim that cardiomyopathy, or heart muscle disease, is common due to taurine deficiency is completely false. Taurine deficiency can case a disease called dilated cardiomyopathy (DCM) in cats, but this disease has almost completely disappeared since commercial diets are supplemented with taurine (unlike the cats eating whole rabbit carcasses, who did develop it in one study). Hypertrophic cardiomyopathy is an entirely different heart disease, which is still fairly common, but this is not associated with taurine deficiency, and Dr. Goldstein appears to be mistakenly conflating the two conditions in his ad.

Euthanized Pets in Commercial Pet Food
This is perhaps the most extreme example of efforts to frighten pet owners about commercial diets. Promoters of this story take a few facts and weave them into an unlikely, but shocking narrative. Most countries have pretty strict regulations about the ingredients that can go into commercial pet foods, and these broad rules cover the use of euthanized animals as a food ingredient even if this is not explicitly mentioned in the law. Industry groups, as well as regulators, also have policies prohibiting this practice. Even apart from such rules and policies, though, the claim makes little sense for other reasons.

Food animals, such as cattle, pigs, sheep, and poultry, are the most common and economical source of animal ingredients for pet foods. These are mostly produced in large operations intended to produce food for humans. Apart from being an ethically terrible and unhealthy ingredient for pet foods, euthanized dogs and cats, presumably harvested from animal shelters or picked up by the roadside, would be an unreliable and expensive raw material compared to the ingredients produced by the food animal industry. And, of course, any company caught using dead pets in their pet food would be destroyed by public outrage and likely run out of business. What motivation these companies might have, then, for using such an ingredient is hard to fathom.

There have been several attempts to investigate commercial pet foods and look for evidence of dog or cat DNA, which might suggest there is some truth to this claim. So far, however, none of these investigations have found evidence that cats and dogs have been used as components of pet foods. The U.S. Food and Drug Administration (FDA), for example, found no evidence of dog or cat DNA in pet foods it tested in 2002. While this can’t definitively prove this practice never happens, it is yet another piece of evidence against it.

So how did this idea get started? It’s impossible to know for certain, but the evidence often cited in support of the claim that euthanized pets are used in pet food tends to be open to interpretation, and those inclined to be suspicious of commercial diets and the companies that produce them seem to take the darkest possible view of this evidence. 

For example, most of the laws and regulations that would prohibit using euthanized pets in pet food don’t actually address that issue directly. The law doesn’t explicitly prohibit the practice precisely because there’s little evidence it is actually occurring. Instead, the laws prohibit unsanitary and unsafe ingredients, potentially dangerous chemicals such as euthanasia drugs, and other general types of ingredients which would naturally include euthanized dogs and cats. Critics of commercial pet foods tend to claim that because the practice isn’t named in the regulations it must actually be happening, which is not a particularly convincing claim.

Animals euthanized at shelters or killed by cars and not claimed are sometimes disposed of at rendering plants, where the bodies are broken down at high temperature into basic components, such as fats and simple proteins. These components are used in a variety of ways, from fats used as industrial lubricants to proteins being used in shrimp and fish farming. This is considered a more environmentally acceptable means of disposal than burning or burying the remains, but it is understandably disturbing to think about. 

Because the parts of food animals not eaten by people are also rendered and are sometimes used in pet foods, there have been concerns that rendering products from euthanized dogs and cats might make their way into pet diets. This is prohibited, again by both regulations and industry policies, and there has not yet been any conclusive evidence that it occurs, but this may be one source of the belief that deceased pets are used as pet food ingredients.

Another, and very serious issue is that the drug pentobarbital, an anesthetic originally used for surgery but now most often used for euthanasia, does sometimes turn up as a contaminate in pet foods. In most of these instances, the amount has been too low to be considered a hazard, but there have been rare cases in which dogs have been sickened and even killed but pentobarbital in canned foods. Investigations into the source of this contamination have typically traced it to the accidental inclusion of euthanized cattle or horses in rendering products intended as pet food ingredients. Once again, no evidence has yet been found showing that euthanized dogs and cats have been the source of pentobarbital contamination of pet foods, but again this may be one source of the belief that this is happening. 

Ultimately, like so many of the concerns raised by critics of science-based medicine and conventional nutrition, it is not possible to conclusively prove that the concern is never true under any circumstances. However, the consistent failure to find evidence for the claim despite repeated investigations over decades certainly makes it an unlikely occurrence and not a reason to fear commercial diets or choose untested alternatives with far less evidence for their safety and nutritional value.

Miscellaneous Claims
Dr. Goldstein uses fear to promote his claims. He tells a sad story about the death of one of his cats from urinary tract obstruction, and claims that commercial cat food caused this, but there is little evidence to support such a claim. He also claims that “more cats are getting sick than ever before,” which is the same kind of mythologizing of the “good old days” that alternative vets often peddle to make people fear the health effects of modern life. I have addressed this claim before in regards to cancer in pets, and there is no evidence to support it and some to suggest that our pets, like us, are healthier than in the past.

Dr. Goldstein also argues that cats should be fed organ meats high in Vitamin D partly because they may become deficient from living indoors or in cold climates due to inadequate sun exposure. This is an idea translated directly from human physiology that simply doesn’t apply to cats. While humans make a lot of our Vitamin D in our skin under the influence of sunlight, cats do not, and they always need to get this from dietary sources regardless of lifestyle (e.g. 34). As I have already mentioned, there is plenty of evidence that cooked commercial diets meet this need effectively.

Bottom Line
Dr. Goldstein is basically trying to sell both a product and the ideology behind it in this infomercial. While I have no doubt he is sincere, there is plenty of reason to doubt he is correct. His claims are based on faulty reasoning and anecdote and often contradicted by established scientific knowledge. There are clear risks to raw diets such as Nature’s Feast, and there is yet no real evidence for any of their purported benefits. Advocates of these diets would better serve the pet population by supporting legitimate, rigorous research to show definitively whether their claims are true or not than by inventing and selling products based on gut feelings and anecdotes and ignoring the science and the real nutrition experts.

Posted in Nutrition | 17 Comments

SkeptVet TV: Vaccine Risks- Real & Imaginary

Research Studies Identifying General Vaccine Risks

Gershwin LJ. Adverse Reactions to Vaccination: From Anaphylaxis to Autoimmunity. Vet Clin North Am Small Anim Pract. 2018 Mar;48(2):279-290. 

Valli JL. Suspected adverse reactions to vaccination in Canadian dogs and cats. Can Vet J. 2015 Oct; 56(10): 1090–1092. 

Moore GE, Hogenesch H. Adverse vaccinal events in dogs and cats. Vet Clin North Am Small Anim Pract. 2010 May;40(3):393-407.

Day MJ. Vaccine side effects: fact and fiction. Vet Microbiol. 2006 Oct 5;117(1):51-8. Epub 2006 Apr 25.

Autoimmune Disease and Vaccines

Cecinati V. Hum Vaccin Immunother. Vaccine administration and the development of immune thrombocytopenic purpura in children. 2013 May;9(5):1158-62.

Huang AA, et al. Idiopathic immune-mediated thrombocytopenia and recent vaccinations in dogs. JVIM 2012; 26: 142-148.

Naleway AL. et al. Risk of immune hemolytic anemia in children following immunization. Vaccine. 2009 Dec 9;27(52):7394-7.

Davidow EB, et al. Risk factors for development of IMHA-A prospective case-control study. Abstract. VECCS 2004.

Carr AP, et al. Prognostic factors for mortality and thromboembolism in canine immune-mediated hemolytic anemia: A retrospective study of 72 dogs. J Vet Internal Med.2002;16:504-509.

Reimer ME, Troy GC, Warnick LD. Immune-mediated hemolytic anemia: 70 cases (1988-1996). J Am Anim Hosp Assoc. 1999;35:384-391.

Duval D et al. Vaccine-associated immune-mediated hemolytic anemia in the dog. J Vet Internal Med. 1996;10:290-295.

Klag AR, et al. Idiopathic immune-mediated hemolytic anemia in dogs: 42 cases (1986-1990). J Am Vet Med Assoc. 1993;202:783-788.

SkeptVet post about Thimerosal 

SkeptVet Posts about Vaccine Dose (12)

All SkeptVet Vaccine Articles

Posted in SkeptVet TV, Vaccines | 5 Comments

No Good News for Veterinary Probiotics

I have covered the subject of probiotics many times in the ten years since the beginning of this blog. I last summarized the evidence in a 2017 post reviewing all of my previous articles as well as the results of a narrative review published that year. My conclusion at that time was:

  • There are few studies, and those that have been done have significant limitations and often conflict.
  • There is reasonable evidence for some clinical benefit in acute diarrhea associated with stress or antibiotic use.
  • There is no high-quality, consistent evidence for most suggested uses of probiotics.
  • The unregulated probiotic products on the market today are plagued with inaccurate labeling and poor quality control. This means that even if probiotics might be beneficial in some cases, it is unclear if the actual products available could achieve these benefits.
  • There do not yet appear to be significant risks to probiotics, though the evidence for this safety also quite limited.

Just this month, a systematic review of probiotics for gastrointestinal (GI) disease in dogs has been published which critically evaluates and summarizes all of the research to date on this subject. 

Jensen AP. Bjornvad CVR. Clinical effects of probiotics in prevention and treatment of gastrointestinal disease in dogs: A systematic review. J Vet Int Med. 2019;33:1849-1964.

Since the most common use of probiotics in veterinary medicine is for gastrointestinal disease, and dogs are the most common species treated (though many cats are treated with probiotics for gastrointestinal problems as well), this is a very relevant and useful review. Given the results of several studies showing that the most common treatment for diarrhea in dogs, the drug metronidazole, probably isn’t effective (1,2,3) probiotics are often seen as a viable alternative, so reliable evidence concerning their effects is needed. Systematic reviews are the most reliable form of evidence summary available, and they can give an accurate overview of the strength of evidence for particular, specific issues in medicine. 

Unfortunately, the news is not good. The review found only 17 clinical studies relevant to whether or not probiotics are useful in canine GI disease. These studies were mostly small and often plagued by significant methodological limitations. The overall conclusions of this review were:

  • the evidence points toward a limited and possibly clinically unimportant effect for prevention or treatment of acute gastrointestinal disease.
  • for chronic gastrointestinal disease, dietary intervention remains the major key in treatment, whereas probiotic supplement seems not to add significant improvement
  • this conclusion is based on a limited number of studies, with a wide methodological diversity, and mainly low sample sizes.
  • there is a high risk that most of the studies evaluated in the current review were severely underpowered especially taking into consideration that baseline characteristics of study groups were generally very poorly documented
  • 12 of the [17] studies reported industry involvement; with such a high degree of industry involvement, there is a risk of publication bias as the incentive to publish studies showing no effect of probiotics could be low

This doesn’t necessarily mean that probiotics aren’t useful or effective for GI disease in dogs. What it does mean is that there isn’t yet any good evidence supporting the use of probiotics for treating or preventing acute or chronic GI disease in dogs, and the evidence we do have is not very reliable. It is very frustrating to see so many research studies done in veterinary medicine that are too small or have other flaws that make it impossible to trust their findings. It is a waste of resources and ethically questionable to conduct studies that don’t do a reasonable job of answering the question they are designed to answer.

At this point, the best we can say about probiotics is that they might be useful but we don’t yet have real evidence to show this, individual products are often mislabeled and quality control is poor, and the risks appear to be low but these haven’t been effectively studied. Ten years since I first wrote about this subject, that is a disappointing level of evidence, and it is frustrating to still be guessing about this treatment.

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