By Brennen McKenzie, MA, MSc, VMD, cVMA

Although cannabidiol (CBD) is the rising star dominating the veterinary market for plant-based remedies these days, there are many others that continue to be used with less fanfare by pet owners and less attention from veterinarians. One of the more popular of these is turmeric.

What is it?

Turmeric is the dried, ground-up root of the plant, Curcuma longa, a relative of ginger. As well as being used as a spice in cooking, this herb has long been employed for a wide range of health conditions in traditional folk medicine, particularly in Indian Ayurvedic and traditional Chinese medicine (TCM). In these folk medicine systems, the principles dictating when to employ specific herbal remedies are unscientific and mystical in nature.

For example, in Ayurvedic traditions, turmeric helps balance the three “doshas,” metaphorical factors believed to be involved in health and disease. Like the humors of traditional Greek humoral medicine, the doshas are associated with personality types, elements such as fire and water, seasons of the year, and many other factors that are perceived as opposites and which Ayurvedic theory suggests need to be balanced to achieve and maintain health. In Ayurvedic medicine, turmeric has been recommended for treatment of arthritis, epilepsy, liver disease, malaria, intestinal worms, gallstones, menstrual problems, cancer, diabetes, Alzheimer’s disease, leprosy, headaches, and innumerable other conditions.^1–3

Similarly, TCM views turmeric as dispelling wind and moving blood and Chi, again relying on metaphorical classifications of invisible entities to guide the herb’s use. It is recommended for pain, arthritis, epilepsy, bleeding, jaundice, urinary calculi, dizziness, ulcers, lactation problems, and as a general tonic or blood purifier.^1,3

These folkloric uses are so broad and based on such ill-defined and untestable principles that they are little different from random trial and error. While traditional applications may sometimes overlap with the use of turmeric based on more scientific guidance, this is not a validation of the traditional practice but simply a function of these traditions having recommended the herb for so many disparate conditions. It illustrates well the adage that even a broken clock is right twice a day.

Preclinical research

Such traditional uses, however, have spurred interest in turmeric, and this has led to more rigorous scientific investigation. The plant’s chemical constituents are numerous and complex, but the most widely cited as potential medicines are the curcuminoids, often referred to collectively as curcumin. This ingredient has many interesting chemical and functional properties illustrated by in vitro and lab animal research. These include anti-inflammatory, immunomodulatory, antineoplastic, and antiseptic properties, as well as other characteristics that might be medically useful.^4–9

However, it is critical we recognize in vitro and animal model studies are not much better than traditional folk uses at predicting the true clinical effects of herbal remedies. Chemical compounds may have activities in lab experiments that they lack in living patients, or they may have unanticipated risks as well as benefits. For example, bleach kills infectious agents and cancer cells in vitro, but it is hardly a useful injectable chemotherapy. It is all too common to assume clinical benefits based on promising preclinical research, but skipping the necessary steps of rigorous clinical trials is a dangerous mistake. There is some debate about whether the basic chemical properties and reported actions of curcumin in laboratory studies make it a promising compound for clinical research and use. However, these properties are widely viewed as justifying clinical studies, and many have been done in humans.^4,10–25

Human trials

Despite hundreds of clinical trials in humans, there is still debate about the value of curcumin for specific health conditions. One of the biggest problems with its use is very poor bioavailability, making it difficult to achieve meaningful levels of the active compound in blood and tissues with oral dosing. Various strategies have been employed to overcome this, including liposome encapsulation and the use of nanoparticles. Further, the variety of dosing formulations complicates comparisons among different products used in research studies and available to the public.⁴

The available research, summarized in systematic reviews, is often conflicting and of less-than-ideal quality. Strong conclusions are rarely justified, but there is some suggestion of benefit for the following conditions: ulcerative colitis (but not Crohn’s disease);^11,15,21,24 weight loss;^14,16 and oral mucositis, as well as some other adverse effects of chemotherapy and radiation therapy.^20,22 The evidence is weak and inconclusive for many other uses of turmeric, including: hypertension;¹² migraines and neuropsychiatric disorders;^18,26 Alzheimer’s disease and other cognitive dysfunction;^19,25 osteoarthritis; and pain.^13,23,27,28

Veterinary research

Inevitably, the veterinary evidence is far more limited than that in humans. Some in vitro and lab animal studies in dogs and cats have suggested anti-inflammatory and antineoplastic effects that might be beneficial. However, these are preliminary and inconsistent, and they don’t justify clinical use.^5–9,29,30 A couple of studies looking at the most popular use of turmeric, for treatment of arthritis, have been disappointing.^31,32 Some subjective owner and investigator measures have suggested an effect, but more objective measures have not shown convincing benefits.

Safety

One of the greatest problems in herbal medicine is the assumption of safety many pet owners and even veterinarians make about herbal remedies. Plant compounds have serious potential risks, regardless of whether they are purified and taken as drugs or ingested directly in plant form. The risks and widespread harm experienced by people due to herbal remedies, from both contaminates and the intended constituents of the remedies, is well established.^33–36

In the case of turmeric, serious adverse effects appear uncommon, largely due to the poor bioavailability of most oral formulations.⁴ However, there have been reports of serious acute liver injury associated with turmeric in humans, and the risks of formulations with greater bioavailability are uncertain.³⁷ As always, there is little regulation or quality control of over-the-counter turmeric supplements for pets, and there is little research data on the potential risks of specific products. Cats, in particular, are more susceptible to toxicoses from plant compounds than humans and dogs, so the safety of largely untested turmeric products in this species cannot be assumed.

Bottom line

Like most minimally tested and regulated herbal remedies for pets, turmeric has some preliminary preclinical evidence suggesting it might have potential benefits for veterinary patients. A few of these purported benefits are supported by studies done in humans, though the human clinical trial literature does not consistently support many recommended applications, including the most popular use as an adjunctive treatment for arthritis pain. There is very little research in dogs and cats, and none that justifies routine clinical use of turmeric for any indication. Few major risks have appeared in the preclinical and human research literature, but in the absence of robust research evidence in dogs and cats, the safety of turmeric cannot be assumed. The widespread popularity of this remedy is not based on legitimate scientific evidence for safety and efficacy, but rather on anecdotal evidence and mistaken reliance on the predictive value of folk medicine traditions.

References

1. Wynn S. Veterinary Herbal Medicine. St. Louis Mo.: Mosby Elsevier; 2007.
2. Gallant L. Turmeric: “The Golden Goddess.” California College of Ayurveda. https://www.ayurvedacollege.com/blog/turmeric/. Published 2009. Accessed September 18, 2020.
3. Prasad S, Aggarwal BB. Turmeric, the Golden Spice: From Traditional Medicine to Modern Medicine. In: Herbal Medicine: Biomolecular and Clinical Aspects. CRC Press/Taylor & Francis; 2011. http://www.ncbi.nlm.nih.gov/pubmed/22593922. Accessed September 24, 2020.
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6. Alkan FU, Anlas C, Cinar S, et al. Effects of curcumin in combination with cyclophosphamide on canine mammary tumour cell lines. Vet Med (Praha). 2014;59(11):553-572. https://www.agriculturejournals.cz/publicFiles/138950.pdf. Accessed September 11, 2020.
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8. Leray V, Freuchet B, Le Bloc’h J, Jeusette I, Torre C, Nguyen P. Effect of citrus polyphenol- and curcumin-supplemented diet on inflammatory state in obese cats. Br J Nutr. 2011;106 Suppl 1:S198-201. doi:10.1017/S0007114511002492
9. Withers SS, York D, Johnson E, et al. In vitro and in vivo activity of liposome-encapsulated curcumin for naturally occurring canine cancers. Vet Comp Oncol. 2018;16(4):571-579. doi:10.1111/vco.12424
10. Daily JW, Yang M, Park S. Efficacy of Turmeric Extracts and Curcumin for Alleviating the Symptoms of Joint Arthritis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. J Med Food. 2016;19(8):717-729. doi:10.1089/jmf.2016.3705
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21. Iqbal U, Anwar H, Quadri AA. Use of Curcumin in Achieving Clinical and Endoscopic Remission in Ulcerative Colitis: A Systematic Review and Meta-analysis. Am J Med Sci. 2018;356(4):350-356. doi:10.1016/j.amjms.2018.06.023
22. Mansouri K, Rasoulpoor S, Daneshkhah A, et al. Clinical effects of curcumin in enhancing cancer therapy: A systematic review. BMC Cancer. 2020;20(1):791. doi:10.1186/s12885-020-07256-8
23. Bannuru RR, Osani MC, Al-Eid F, Wang C. Efficacy of curcumin and Boswellia for knee osteoarthritis: Systematic review and meta-analysis. Semin Arthritis Rheum. 2018;48(3):416-429. doi:10.1016/j.semarthrit.2018.03.001
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28. Daily JW, Yang M, Park S. Efficacy of Turmeric Extracts and Curcumin for Alleviating the Symptoms of Joint Arthritis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. J Med Food. 2016;19(8):717-729. doi:10.1089/jmf.2016.3705
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Brennen McKenzie, MA, MSc, VMD, cVMA, discovered evidence-based veterinary medicine after attending the University of Pennsylvania School of Veterinary Medicine and working as a small animal general practice veterinarian. He has served as president of the Evidence-Based Veterinary Medicine Association and reaches out to the public through his SkeptVet blog, the Science-Based Medicine blog, and more. He is certified in medical acupuncture for veterinarians. Columnists’ opinions do not necessarily reflect those of Veterinary Practice News.