Is Garlic Toxic for Dogs? The Facts (and Fiction)

Garlic Poisonous for Dogs? Myth Debunked.

Summary

Garlic has been both praised for its numerous health benefits and criticised for its potential toxicity in dogs. This article delves into the myths and facts surrounding garlic, examining its health benefits, the misconceptions about its toxicity, and guidelines for safe garlic consumption in dogs. By exploring scientific research and historical use, this article aims to clarify the role of garlic in canine nutrition and offer practical advice for dog owners.

Table of Contents

• Introduction
  • Understanding the Garlic Debate
• The Historical Use of Garlic for Medicinal Purposes
• The Benefits of Garlic for Dogs
  • Garlic as a Natural Medicine
  • Key Health Benefits
• Why Do Dog Owners Avoid Garlic?
  • The Allium Family Confusion
  • Thiosulfate: The Real Culprit
• The Flawed Research That Caused the Garlic Misunderstanding
  • The 2000 Study: A Deeper Look
• How Much Garlic Is Toxic for Dogs ?
  • How Much Garlic Can Dogs Eat Daily? Recommended Dosages
  • National Research Council Guidelines
  • Tips for Safe Garlic Administration
• Are Garlic Supplements Just As Beneficial?
  • Fresh vs. Processed Garlic
• The Preparation of Garlic for Dogs
  • Best Practices for Feeding Garlic
  • Cautionary Notes
• Garlic Poisoning in Dogs
  • Causes of Garlic Poisoning
  • Symptoms of Garlic Poisoning
  • Treatment for Garlic Poisoning
• Conclusion
  • Final Thoughts on Garlic in Canine Diets

Introduction

Garlic has been a staple in human diets and herbal medicine for thousands of years, valued for its numerous health benefits. However, when it comes to dogs, garlic has sparked considerable debate. Some believe garlic is toxic to dogs, while others advocate for its medicinal use in small doses. This article aims to separate fact from fiction, providing dog owners with the most accurate and up-to-date information on garlic’s safety and benefits.

The Historical Use of Garlic for Medicinal Purposes

Garlic (Allium sativum) has a long and storied history as a medicinal herb, with its use dating back thousands of years across various cultures. The earliest recorded use of garlic dates to ancient Egypt, where it was prized not only as a flavouring agent but also as a powerful medicinal remedy. Workers constructing the Great Pyramid of Giza were fed garlic daily to boost their stamina and protect against diseases. Garlic was also placed in the tomb of Pharaohs as an offering to the gods.

In ancient Greece, garlic was used by soldiers before battle to enhance their strength and endurance. Hippocrates, often referred to as the father of medicine, prescribed garlic for a variety of conditions, including respiratory problems, poor digestion, and fatigue. The Romans also valued garlic for its health benefits, feeding it to their soldiers and sailors to promote vitality and ward off infections.

Garlic’s medicinal properties were recognised in traditional Chinese medicine over 3,000 years ago. It was used to treat respiratory and digestive disorders, boost immunity, and as an antiseptic for wounds. Similarly, in Ayurvedic medicine, garlic was used as a remedy for a wide range of ailments, including heart disease, arthritis, and digestive issues.

Native Americans also incorporated garlic into their healing practices, using it to treat coughs, earaches, and infections. Throughout medieval Europe, garlic was a popular remedy during plagues, believed to protect against illness.

The bioactive compounds in garlic, such as allicin, which is released when garlic is crushed or chopped, are largely responsible for its therapeutic effects. These compounds exhibit antimicrobial, anti-inflammatory, and immune-boosting properties, making garlic a valuable tool in both ancient and modern medicine.

The Benefits of Garlic for Dogs

Garlic as a Natural Medicine

Garlic (Allium sativum) belongs to the same botanical family as onions, leeks, chives, and shallots. This association often leads to confusion about garlic’s safety for dogs, but it’s important to recognise that garlic has been used for centuries in both human and animal medicine. Ancient Egyptians, Chinese doctors, and Native Americans all utilised garlic for its powerful healing properties.

Garlic is rich in essential vitamins, minerals, and bioactive compounds, including allicin and ajoene, which contribute to its reputation as a near-miraculous remedy. These compounds are known for their anti-inflammatory, antimicrobial, and immune-boosting effects. When used appropriately, garlic can be a valuable addition to your dog’s health regimen.

Key Health Benefits

Garlic offers a multitude of health benefits due to its rich composition of nutrients:

• Detoxification: Garlic supports liver function by breaking down toxins and aiding in their elimination through the digestive tract. This detoxifying effect is particularly beneficial during seasonal changes or after exposure to environmental toxins.
• Immune System Boost: Garlic enhances the immune system, helping dogs fight off infections and recover more quickly from illnesses. It is particularly useful during cold seasons to protect against respiratory infections.
• Improved Circulation: The sulphur compounds in garlic help widen blood vessels, reduce cholesterol levels, and prevent the formation of blood clots, which can contribute to better cardiovascular health.
• Antimicrobial and Antifungal Properties: Garlic’s natural antibiotic properties make it effective in combating harmful bacteria, fungi, and parasites, including worms. It can be a useful addition to a holistic approach to treating infections and infestations.
• Anticancer Potential: Studies have suggested that the sulphur compounds in garlic may help in preventing the formation of certain types of cancer. While these studies are primarily based on human data, the potential benefits for dogs are worth considering.

Why Do Dog Owners Avoid Garlic?

The Allium Family Confusion

One of the main reasons dog owners avoid garlic is its inclusion in the Allium family, which also contains onions, leeks, chives, and shallots. These other members of the Allium family are known to contain high levels of thiosulfate, a compound that is toxic to dogs. This has led to a blanket fear of all Allium vegetables, including garlic.

Thiosulfate: The Real Culprit

Thiosulfate can cause oxidative damage to a dog’s red blood cells, leading to the formation of “Heinz bodies,” which are abnormal structures that the body recognises as damaged. The immune system then removes these damaged cells, leading to a condition known as haemolytic anaemia. This condition can be severe, but it’s important to note that garlic contains significantly less thiosulfate than onions, making the risk of toxicity much lower.

The Flawed Research That Caused the Garlic Misunderstanding

The 2000 Study: A Deeper Look

The belief that garlic is toxic to dogs can largely be traced back to a 2000 study conducted by Lee et al. in Japan. In this study, dogs were fed an extremely high dose of garlic—approximately 5 grams of garlic per kilogram of the dog’s body weight each day for a week. To put this into perspective, a 20-kilogram dog would have consumed 100 grams of raw garlic daily, equivalent to about 20 cloves.

While the study did show changes in the dogs’ blood parameters, indicating oxidative damage to the red blood cells, none of the dogs developed clinical signs of hemolytic anaemia. Despite this, the researchers concluded that garlic should be avoided in dog food, a conclusion that has since been widely misinterpreted and led to the widespread belief that garlic is toxic to dogs.

Reference: Lee, K.W., Yamato, O., Tajima, M., Kuraoka, M., Omae, S., & Maede, Y. (2000). A study on the hemolytic effect of garlic in dogs. Journal of Veterinary Medical Science, 62(10), 1055-1056. doi:10.1292/jvms.62.1055. (1)

Since the publication of the above research a number of studies have researched the impact of garlic on dog health. These have demonstrated that garlic toxicity proposed in the Lee study has been incorrectly assigned.

A study conducted by Chang and colleagues in 2004 clearly demonstrated that allicin provides health benefits to mammals without causing haemolytic anaemia, even at high doses of garlic. The study found that “the maximal aggregation percentage returned to the control level at 1mM of all(en)yl thiosulfates in both canine and human platelets,” indicating that the levels did not remain elevated enough to pose a risk, contrary to earlier concerns. As a result of these findings, scientists revised their earlier recommendations based on the 2000 study and began to advocate for the use of garlic to enhance immune function and support cardiovascular health in dogs.

Reference: Chang 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. Prostaglandins Leukot Essent Fatty Acids. 2004 Jan;70(1):77-83. doi: 10.1016/j.plefa.2003.08.006. PMID: 14643182.

A further study published in 2018 by Osamu Yamato et al ‘Safety and efficacy of aged garlic extract in dogs: upregulation of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway and Nrf2-regulated phase II antioxidant enzymes‘, concluded ‘The long-term oral administration of AGE (aged garlic extract) at a dose of 90 mg/kg/day for 12 weeks did not show any adverse effects in dogs. Furthermore, the administration of AGE upregulated the gene expressions of canine Nrf2 and Nrf2-regulated phase II antioxidant enzymes. These results suggest that AGE might safely contribute to the health of dogs provided that the appropriate dosage is used.

Reference: Yamato O, Tsuneyoshi T, Ushijima M, Jikihara H, Yabuki A. Safety and efficacy of aged garlic extract in dogs: upregulation of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway and Nrf2-regulated phase II antioxidant enzymes. BMC Vet Res. 2018 Nov 29;14(1):373. doi: 10.1186/s12917-018-1699-2. PMID: 30497454; PMCID: PMC6267818.

How Much Garlic is Toxic for Dogs?

How Much Garlic Can Dogs Eat Daily? Recommended Dosages

When it comes to garlic, moderation is key. The following dosage guidelines are based on your dog’s weight according to the dosage recommendations in Juliette de Bairacli Levy’s book, The Complete Herbal Book for the Dog. ( a guide followed by many vets and practitioners):

• 4.5 to 7 kg: ½ clove per day
• 9 to 18 kg: 1 clove per day
• 20 to 32 kg: 2 cloves per day
• 34 to 41 kg: 2½ cloves per day
• 45 kg and over: 3 cloves per day

Based on a garlic clove weighing approximately 3 grams, the PSI for a 23-kilogram (50-pound) dog is 1.2 grams per day, which is roughly equivalent to just less than half a clove per day.

These dosages are designed to provide the health benefits of garlic without risking toxicity. It is important to note that garlic cloves vary greatly in size, with one clove garlic = 3 g to 7 g.

National Research Council Guidelines

A 2008 report published by the National Research Council offers a more conservative approach to garlic dosage. While the committee that prepared the report was unable to determine the safe upper limit of garlic intake for dogs, cats, and horses, it used available research to recommend a range of acceptable intakes according to historical safe intakes (HSI) and estimated presumed safe intakes (PSI). (2)

Garlic Consumption Milligrams per Kilogram Bodyweight

In this table:

• Presumed Safe Intake (PSI) is calculated using the average weight of the range multiplied by 56.
• Historical Safe Intake (HSI) is calculated using the average weight of the range multiplied by 22.

Tips for Safe Garlic Administration

When introducing garlic to your dog’s diet, begin with a small dose and increase gradually. This allows your dog to become accustomed to the taste of garlic and helps to avoid any digestive upset. Additionally, garlic should preferably be given in its raw, fresh form to ensure maximum benefits.

Are Garlic Supplements Just As Beneficial?

Fresh vs. Processed Garlic

While garlic supplements are available, they are generally less effective than fresh garlic. The processing involved in creating garlic powders, capsules, and other supplements often destroys the active compounds that give garlic its medicinal properties, particularly allicin which is heat sensitive. (3)

If you choose to use a garlic supplement, look for garlic extracts, which retain more of the beneficial compounds. However, whenever possible, fresh garlic should be your first choice for feeding your dog.

The Preparation of Garlic for Dogs

Best Practices for Feeding Garlic

To maximise the health benefits of garlic, it is crucial to use fresh, organic garlic. Here are some tips for preparing garlic for your dog:

1. Use Fresh Garlic: Always opt for fresh, organic garlic over processed or pre-chopped garlic, which may contain preservatives and lose its medicinal properties.
2. Chop, Mince, or Crush: Chop, mince, or crush the garlic and let it sit for about 10 minutes before adding it to your dog’s food. This waiting period allows the formation of allicin, the bioactive compound responsible for garlic’s health benefits.
3. Introduce Slowly: Start with a small amount and gradually increase the dose over several days. This approach helps your dog acclimate to the taste and ensures that they receive the benefits without any adverse effects.

Cautionary Notes

Garlic can interact with certain medications, including heart medications, blood thinners, and insulin. Additionally, some dog breeds, particularly Japanese breeds like Shiba Inus and Akitas, may be more sensitive to garlic. It is always wise to consult with your veterinarian before adding garlic to your dog’s diet, especially if they have any pre-existing health conditions.

Garlic Poisoning in Dogs

Despite the numerous benefits of garlic, it is important to be aware of the potential for garlic poisoning, though it is rare and generally occurs only with excessive consumption.

Causes of Garlic Poisoning

Garlic poisoning in dogs is typically caused by the ingestion of large quantities of garlic, far beyond the recommended dosages. This can happen if a dog gets into a garlic-rich food source or if a well-meaning owner inadvertently gives too much garlic over a period of time.

Symptoms of Garlic Poisoning

The symptoms of garlic poisoning may not appear immediately and can take several days to manifest. They include:

• Vomiting
• Diarrhoea
• Lethargy
• Increased heart rate
• Pale gums (a sign of anaemia)
• Weakness
• Abdominal pain
• Collapse (in severe cases)

If you notice any of these symptoms after your dog has consumed garlic, it is important to seek veterinary care immediately.

Treatment for Garlic Poisoning

Treatment for garlic poisoning will depend on the severity of the symptoms and the amount of garlic consumed. In mild cases, your veterinarian may recommend supportive care, such as intravenous fluids to flush out the toxins and medications to manage symptoms like vomiting and diarrhoea.

In more severe cases, where anaemia has developed, a blood transfusion may be necessary. The key to successful treatment is early intervention, so it is crucial to seek veterinary advice as soon as you suspect garlic poisoning.

Conclusion

Garlic, when used in moderation, can be a valuable addition to your dog’s diet. It offers numerous health benefits, from boosting the immune system to improving circulation and acting as a natural antibiotic. However, like many things, garlic must be used responsibly to avoid the risk of toxicity.

The fear of garlic poisoning is largely based on misconceptions and misinterpreted research. By following safe dosage guidelines and consulting with your veterinarian, you can confidently include garlic in your dog’s diet and enjoy its many benefits.

In conclusion, garlic has much to offer when it comes to canine health, but it should be used with care. Always consult with your vet before making any significant changes to your dog’s diet, especially if your dog is on medication or has a pre-existing condition. With the right approach, garlic can be a powerful ally in maintaining your dog’s health and well-being.