Learn and understand the myth’s surrounding garlic and its supposed toxicity, and discover the many health benefits it offers dogs and cats.
When it comes to your patients’ health – preventatively or curatively – you need accurate information about safety and benefits. Garlic, long used as a beneficial herb, and listed by the FDA as approved for pet food, is still under attack in spite of a 2004 follow-up study recommending garlic for dogs by the majority of scientists involved in a 2000 study done by Japan. Even the ASPCA’s poison hotline information recently added garlic to its list of toxins, although they report no individual cases linked to garlic ingestion in 2014, as they do for most other toxins. While it is understandable that you may hesitate to prescribe garlic, the facts below may shift your thinking. BENEFITS For centuries, humans have used herbs, and garlic has been a primary remedy for a large number of symptoms. As long as people have been using garlic, they have also been feeding it to their animal companions; some animals enjoy foraging for it, as my dog, Lady, loved to do.
Garlic’s properties have proven far-reaching, easily assimilated, and safe. In the past 80 years, during holistic medicine’s rebirth in the United States, garlic has been in the forefront of both human care and animal husbandry. Every textbook I have researched on herbal medicine that also mentions pet care recommends it, especially for its incredible anti-parasitic, anti-carcinogenic, and antiseptic properties. In my own experience, garlic has also benefited animals with valley fever (Coccidioidomycosis), heartworm/fleas/ticks, IBS, diabetes, liver, heart and kidney disease, allergies, uncontrollable staph infections (that are non-responsive to all antibiotic protocols), and a host of other conditions. Garlic is also a staple in my preventative protocols.
Garlic has been widely and safely used by hundreds of thousands of Azmira pet parents for over 30 years, with no reported serious negative side effects – except on the breath.
Separating fact from fiction
For the last few decades, primarily as a result of the onion’s reputation for triggering Heinz body hemolytic anemia because of its higher concentration of thiosulphate, garlic (the onion’s “kissing cousin”) was also said to be toxic. Garlic simply does not contain the same thiosulphate concentration as the onion does. In fact, it is barely traceable and readily excreted. “In the testing of onions and garlic on (the dog’s) blood cell oxidation, onions have about 15 times the ability of garlic to damage red blood cells,” states nutritionist Dr. Dave Summers on IndigoPetz.com.1
Almost all the “evidence” against garlic for dogs comes from a 2000 study at Hokkaido University.2 Four dogs were each given 1.25 ml of garlic extract per kg of body weight for seven straight days. For example, if the dog weighed 50 pounds, he would be given approximately 25 large raw garlic cloves. None of the dogs showed any outward toxicity symptoms, but there was an effect on their red blood cells, even though at these highly-elevated doses none of the dogs developed anemia. “We believe that foods containing garlic should be avoided for use in dogs,” the researchers stated. However, a study published by Chang, et al in 20043 clearly showed that allicin is beneficial to mammals’ health, and there was no report of hemolytic anemia in spite of the high concentrations of garlic provided during the study. “In contrast, the maximal aggregation percentage returned to the control level at 1mM of all(en)yl thiosulfates in both canine and human platelets,” rather than remaining high enough to be a problem as originally thought. This encouraged the scientists to reverse their earlier 2000 recommendations against garlic for dogs and actually recommend garlic to promote immune functions and prevent cardiovascular diseases.
There can be multiple causes for Heinz body hemolytic anemia. Wendy Wallner, DVM, reminds us that other substances such as acetaminophen (Tylenol) and benzocaine-containing topical preparations can also cause Heinz body hemolytic anemia in the dog. These preparations probably account for many cases since ingredients in creams are absorbed through the skin, allowing toxins to build up in the bloodstream.
Use of garlic in your practice
Garlic works through physical means. It can interfere with medications, especially blood thinners, so it is best to research possible drug interactions. Although herbs and supplements may be “natural”, they should be respected and researched so you can understand and evaluate their full value to your practice.
Powdered garlic, and indeed encapsulated dry herbs of any kind, are so weak that they barely perform. “Deodorized” garlic lacks active allicin (enzymatic actions are noticeably stinky), and tableted supplements weaken digestive processes with potentially toxic binders (brewer’s yeast, flavoring). Glycerol-suspended garlic products, although tasty, form a moisture barrier inhibiting mucous membrane and cellular assimilation. Cold pressing garlic maximizes the benefits – Azmira’s Garlic Daily Aid is 1,000 mg of cold pressed garlic plus 500 mg of parsley oil in individual gelcaps, which also protect against oxygen exposure.
Garlic’s sulphur-inclusive compounds
Garlic contains multiple sulphur-inclusive compounds – alliin, a noted sulfoxide; and alliinase, an enzyme. When garlic is chopped, crushed, minced or chewed, the alliinase enzyme is activated, and combines with the alliin protein to produce allicin, the therapeutic component of garlic. Heat inactivates enzymes, so by waiting at least ten minutes after chopping so the enzyme has completed the reaction with the alliin, the therapeutic value is maximized. Allicin is heat stable.
Safe raw garlic dosages for dogs and cats
Many veterinary practitioners and authors follow the dosage recommendations in Juliette de Bairacli Levy’s book, The Complete Herbal Book for the Dog. She recommends:
- 10 to 15 pounds – ½ clove
- 20 to 40 pounds – 1 clove
- 45 to 70 pounds – 2 cloves
- 75 to 90 pounds – 2½ cloves
- 100 pounds and over – 3 cloves
A 2008 report published by the National Research Council is more conservative in its dosage information. While the committee that prepared the report was unable to determine the safe upper limit of garlic intake for dogs, cats and horses, it could “use available research to recommend a range of acceptable intakes according to historical safe intakes (HSI) and estimated presumed safe intakes (PSI)”.4
Based on a clove weighing 3 g, the PSI for:
- A 50 lb. dog is 1.2 g or .045 ounces/day, which is equivalent to approx. ½ clove per day
- A 15 lb. cat is .12 g or .004 ounce/day, which is equivalent to approx. 1/25 clove per day
- An 850 lb. horse is 34.8 g or 1.2 ounces/day, which is equivalent to approx. 11 cloves.
Remember that garlic cloves vary greatly in size, with one clove garlic = 3 g to 7 g. As with any herbs, I believe it is always a good idea to take a week off from garlic every couple of months.
While garlic is safe to use, keep the following in mind when selecting and prescribing it for your patients:
- Select companies that avoid sourcing garlic extract from China, as it is often contaminated with high levels of arsenic, lead and added sulfites.
- Raw garlic fed directly is high in insoluble fiber and certain sulfur compounds, so it could be a potential issue for dogs that have oral ulcerations, esophageal obstructions, reflux, IBS or colitis.
- When used in the dosages given above, garlic is safe even for pregnant dogs. The only caution is that overly large ingested quantities may flavor the milk of lactating females and turn off the pups from nursing, so start with small doses if nursing problems exist.
1Summers D. “Understanding Garlic”. IndigoPetz.com or facebook.com/permalink.php?id=125654427474116&story_ fbid=643173565722197; October 10, 2013.
2Lee KW, Yamato O, Tajima M, Kuraoka M, Omae S, Maede Y. “Hematologic changes associated with the appearance of eccentrocytes after intragastric administration of garlic extract to dogs”. Am J Vet Res. 2000 Nov:61 (11): 1446-50.
3Chang HS, Yamato O, Sakai Y, Yamasaki M, Maede Y. “Acceleration of superoxide generation in polymorphonuclear leukocytes and inhibition of platelet aggregation by alk(en)yl thiosulfates derived from onion and garlic in dogs and humans”. Department of Veterinary Clinical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, 060-0818 Sapporo, Japan, 2004.
4Riviere Jim E, Boothe Dawn M, Czarnecki-Maulden Gail L, Dzanis David A, Harris Patricia A, Hendriks Wouter H, Kirk Claudia A, Warren Lori K, Lewis Austin J, Arieti Ruth S. “Safety of Dietary Supplements for Horses, Dogs, and Cats”. Committee on Examining the Safety of Dietary Supplements for Horses, Dogs, and Cats, The National Academy of Sciences, 2008.