Garlic: Is It Safe For Your Pet?

In this article, we delve into the issues surrounding garlic’s safety for pets.

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Garlic is a very controversial ingredient for pets, yet many popular pet foods and supplements contain garlic in their ingredients lists. For most people, this causes justifiable concern. After all, in an attempt to promote optimum health in our pets, we do not want to do anything that will harm them. In this article, I take a closer look at garlic and give you some guidelines to go by when deciding if a food containing garlic is safe and appropriate for your pet.

Please note that this article discusses garlic as it pertains to dogs. You should never give garlic (even a tiny amount) or any product containing garlic to cats, as cats are more susceptible to garlic toxicity than dogs.

Let’s begin with some background information about garlic.

What is Garlic?

Garlic is a member of the Allium family, a genus of flowering plants that also includes onions, chives, scallions, leaks and shallots (all of which should never be given to dogs or cats!).

Allium plants contain components called disulfides, which are chemical compounds containing two sulfur atoms per molecule. Disulfides have been implicated as toxic for animals including dogs, cats and horses. N-propyl disulfide is considered the primary toxic disulfide.

Disulfides are oxidizing and can damage the animal’s red blood cells, causing them to rupture (hemolysis) and resulting in bubble-like pieces of oxidized hemoglobin on the outside of the cells called “Heinz” bodies. Since red blood cells carry oxygen to the tissues, a reduction in their numbers causes a type of anemia called Heinz body hemolytic anemia. Humans do not suffer from this problem as we are very resistant to disulfides; however, dogs, cats and horses are very susceptible.

Signs of Allium Toxicosis

Clinical signs of Allium toxicosis can appear as soon as one day if a dog or cat ingests large amounts of a food in the Allium species, however it can take up to several days for signs to appear.^[1]

The earliest signs are generally related to the gastrointestinal system and include:

• Vomiting
• Diarrhea
• Abdominal pain
• Loss of appetite
• Depression
• Dehydration

Later signs resulting from the loss of red blood cells include:

• Weakness
• Lethargy
• Pale mucous membranes
• Rapid respiratory rate
• Difficulty breathing
• Rapid heart rate
• Jaundice
• Dark colored urine

Two Interesting Studies

So, if garlic is part of the Allium family and potentially toxic, why is it often included in pet foods and supplements? The issue, according to my dear friend and veterinary hematologist Dr. Jean Dodds, DVM, is one of dosage.

Let’s take a closer look at two studies that illustrate the importance of proper dosing.

Potential Benefits of Proper Garlic Dosing
A study published in 2011 compared the effectiveness of garlic with the popular prescription anti-diabetic drug metformin in lowering blood glucose levels in diabetic dogs. The dogs were given an orally-administered daily dosage of 100 mg of garlic per kilogram of body weight.^[2] Since a typical clove of garlic weighs 3 grams (3,000 mg) ^[3], 100 mg is equal to one-thirtieth (1/30) of a clove of garlic – a very tiny amount! According to the researchers, “In this study, the dosage of garlic was chosen to be 100 mg/kg since it is a safe amount of garlic to be given daily and does not cause toxicity.”^[2]

Interestingly, the researchers found that, “Garlic had a mild, but significant, blood glucose-lowering effect and the long-term use of this substance may be advantageous over chemical drugs in alleviating some of the chronic diseases and complications caused by diabetes.”^[2] This study is an excellent example of the potential benefits of garlic when used appropriately.

Too Much of a Good Thing
An often-cited study published in 1999 has scared many people away from giving any amount of garlic to dogs. In this study, the researchers attempted to identify whether dogs given garlic extract for seven days developed hemolytic anemia, as well as to identify any resulting changes that occurred in their blood.

What I find most fascinating about this study was the dosage of garlic used.

The dogs were given 1.25 ml of garlic extract per kg of body weight daily, an amount that the researchers stated was equivalent to 5 grams of whole garlic/kg of body weight daily.^[4]

As we said, one clove of raw garlic weighs about 3 grams ^[5], so 5 grams is equal to slightly more than 1.5 cloves. Since the dogs receiving the garlic weighed an average of 12.2 kg (about 27 pounds) and were given the equivalent of 5 grams (5,000 mg) of whole garlic/kg of body weight daily, each dog was given the equivalent of close to 20 cloves of garlic per day!

The dogs in this study received more than 50 times the known safe dosage of garlic.

So, what was the result? When the researchers analyzed the dogs’ blood, they identified signs of hemolysis (premature destruction of red blood cells), which is not surprising given the mega-doses of garlic that were administered. However, none of the dogs developed any clinical signs of hemolytic anemia.^[5]

These two studies illustrate the difference between the potential beneficial effects of garlic for pets when given in a safe, appropriate dose compared to the negative effects when administered at excessive levels.

Garlic in Commercial Pet Products

Pet food manufacturers and supplement producers who use garlic recognize the beneficial properties for dogs when used in safe, appropriate dosages. Here are some guidelines to follow when purchasing a commercial pet food or supplement containing garlic:

• Check that garlic is listed toward the end of the ingredients list, and certainly not within the first 10 ingredients. Remember that the lower down on the list an ingredient is, the less of it by weight the product contains.
• Only purchase foods or supplements containing garlic that are specifically formulated for pets.
• Seek out a reputable pet food/supplement manufacturer to ensure quality, purity and proper dosing.

The Take-Away

Garlic in small amounts has potential health benefits for dogs, such as identified in the 2011 canine diabetes study. However, there are some guidelines that I strongly urge you to follow to ensure that your pet gains the benefits of garlic without any potential harm:

• Follow the guidelines above regarding purchasing pet foods and supplements containing garlic.
• Never give garlic (even a tiny amount) or any products containing garlic to cats, as they are more susceptible to the toxic effects than dogs.
• Use extreme caution giving garlic in any form or in any amount to Japanese dog breeds, such as Akitas and Shiba Inus, as they are more susceptible to garlic toxicity than other breeds.
• Avoid concentrated forms of garlic, such as garlic powder, dehydrated garlic or soup mixes, as these are more potent and have greater potential to cause toxicity.
• Avoid prepared foods intended for humans that contain garlic, as these have a greater potential to contain amounts that can result in toxicity.
• Avoid human supplements containing garlic, as they may include levels that are toxic for dogs.
• Use extreme caution giving your dog garlic prepared at home. It is very difficult to know if you are “crossing the line” into a toxic amount, and you could be asking for trouble.

I hope this article cleared up any confusion you may have had regarding garlic and pets. As always, I welcome your thoughts!

References

1. ^[1] Cope, RB 2015, Toxicology Brief: Allium species poisoning in dogs and cats, DVM360, Retrieved from http://veterinarymedicine.dvm360.com/toxicology-brief-allium-species-poisoning-dogs-and-cats. ↩
2. ^[2] Mosallanejad1, B, Avizeh, R, Najafzadeh Varzi, H and Pourmahdi, M 2011, ‘A comparison between metformin and garlic on alloxan-induced diabetic dogs’, Comparative Clinical Pathology, vol. 22, no. 2, pp 169-174. ↩
3. ^[3] SelfNutritionData 2014, Garlic, raw, Retrieved from http://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2446/2 ↩
4. ^[4] Lee, KW, Yamato, O, Tajima, M, Kuraoka, M, Omae, S and Maede, Y 1999, ‘Hematologic changes associated with the appearance of eccentrocytes after intragastric administration of garlic extract to dogs’, American Journal of Veterinary Research, vol. 61, no. 11, pp. 1446-1450. ↩
5. ^[5] SelfNutritionData 2014, Garlic, raw, Retrieved from http://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2446/2 ↩
6. ^[5] Lee, KW, Yamato, O, Tajima, M, Kuraoka, M, Omae, S and Maede, Y 1999, ‘Hematologic changes associated with the appearance of eccentrocytes after intragastric administration of garlic extract to dogs’, American Journal of Veterinary Research, vol. 61, no. 11, pp. 1446-1450. ↩

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