Garlic: Despite its toxic reputation, this ingredient is actually safe
Garlic has a bad reputation among most veterinary professionals because it belongs to the onion family. However, unlike other vegetables in the Allium family, garlic is safe for dogs because its concentration of thiosulfate (the toxic component in onions) is significantly lower compared to other vegetables in this family.
The Confusion About Garlic Toxicity
The main reason for the conflicting information is that most studies related to garlic base their findings on the effects of garlic extracts, excessive doses, and unnatural methods of administration. In these studies, researchers rarely use fresh garlic because it is difficult to measure the medicinal variations in whole plants.
One particular study in 2000 by K.W. Lee et al. contributed to garlic’s toxic reputation for dogs. In this study, researchers wanted to know if administering large amounts of garlic extract could cause hemolytic anemia and what dose would be necessary for this to occur.
The dogs in the study received 1.25 ml per kg of garlic extract (equivalent to 5g of raw garlic per kg per day), once a day for seven days.
This is an excessive amount! It would be equivalent to feeding around four heads of garlic (or 60 cloves) to a 34kg Golden Retriever or 23 grams of garlic (6 to 8 cloves) to a 5kg dog to see if they showed side effects.
We definitely should not be feeding these doses, nor would our dogs want to eat that much garlic!
Even so, the results showed that even this amount did not cause anemia, but instead caused microscopic oxidative stress changes in red blood cells. This was enough for the researchers to claim that large amounts of garlic extract are not safe for dogs, which was later misinterpreted as "all types of garlic in all amounts."
The dosage involved in the initial study was so unrealistic that the original authors decided to conduct a follow-up study in 2004. This time, they reversed their initial position on garlic and stated that this ingredient actually has the potential to promote immune function and reduce the risk of cardiovascular diseases in dogs.
In another study in 2018, the amounts of garlic offered were much smaller and over a longer period (12 weeks instead of 7 days). In this study, the dose offered was 90mg per kg per day, and they concluded that “oral administration over the long term at a dose of 90 mg/kg/day for 12 weeks did not show adverse effects in dogs.”
In this study, researchers found a benefit: garlic positively regulated the genetic expressions of canine antioxidant enzymes Nrf2 (nuclear factor erythroid 2-related factor 2) and Nrf2-regulated phase II enzymes. Nrf2 plays a crucial role in cellular defence against oxidative stress.
Despite this, the idea that garlic is unsafe still persists.
Thiosulfate in Garlic
Garlic contains thiosulfate, a chemical compound that can cause Heinz body hemolytic anemia. This type of anemia causes oxidative damage to red blood cells, which are responsible for oxygenating tissues. Hemolytic anemia leads to a decrease in these cells, which can result in illness or even death in severe cases. Symptoms of haemolytic anemia include pale or yellow gums, loss of appetite, vomiting, diarrhea, lethargy, exercise intolerance, increased respiratory rate, increased heart rate, dark orange or brown urine, weakness, and collapse.
So, how can you avoid the risk of hemolytic anemia? Simply feed fresh garlic in the correct dose.
Adequate doses of fresh garlic do not contain high levels of thiosulfate, and since the bone marrow continuously produces red blood cells, it means that an animal would have to receive an excessive dose over a long period, or an extremely large dose in a short time, to cause death.
Why Offer Garlic?
Garlic is rich in inulin, amino acids, sulfur, zinc, potassium, and phosphorus. It also contains vitamins A, C, calcium, magnesium, manganese, selenium, germanium, and B vitamins. It helps detoxify the body, supports beneficial bacteria in the digestive tract, and eliminates harmful bacteria.
Other benefits of garlic include:
Helps prevent blood clot formation
Lowers blood glucose, triglycerides, and cholesterol levels
Improves immune system response
Acts as a vasodilator for blood vessels
Has anticancer properties
Stimulates the lymphatic system
Has antibacterial, antifungal, and antiparasitic effects
Using Garlic as a Natural Repellent for Fleas, Ticks, and Mosquitoes
Feeding garlic can help in the battle against fleas, ticks, and mosquitoes, making its use very beneficial during the months when these parasites are most active.
It takes some time for garlic's repellent compounds to accumulate in the dog's natural coat oil, so it’s ideal to start offering garlic before spring arrives.
Garlic and Its Anticancer Properties
The sulfur compounds in garlic have anticancer properties.
A study published in Cancer Letters evaluated the impact of garlic’s organosulfur compounds on canine mammary tumour cells. The results of this study demonstrated that these compounds significantly inhibited the growth of neoplastic cells.
Another study published by Anti-Cancer Agents in Medicinal Chemistry supports the anticancer effects of garlic sulfur compounds, further highlighting their mechanisms of action, including the metabolization of enzymes responsible for carcinogen detoxification, inhibiting reactive oxygen species, and inducing apoptosis, among other actions.
What Amount of Garlic Is Safe to Give My Dog?
Only use fresh garlic. Do not use garlic capsules, garlic oil, garlic powder, garlic essential oil, or pre-minced garlic (sold in supermarkets). To get the benefits of garlic, it must be fresh and raw in its most natural state.
And why? Only when using raw garlic do we obtain all the nutritional and medicinal benefits of the plant. Also, because only then will we have the active compound in garlic, allicin. Allicin is the active medicinal compound that offers garlic’s antibiotic, antiviral, anticancer, and antioxidant properties.
The interesting thing about allicin is that it is not naturally present in garlic. Only when we crush, smash, or finely chop the garlic does the enzyme alliinase combine with the protein alliin, and after 10 to 15 minutes, allicin is formed. That’s why it’s essential to use fresh garlic and crush it just before serving it to your animal. Allicin degrades quickly over time, so it’s ideal to offer the garlic shortly after waiting the 10 to 15 minutes.
Dosage
- Miniature dogs (up to 5kg): 1/8 to 1/6 of a garlic clove per day
- Small dogs (5-10kg): 1/4 to 1/2 of a garlic clove per day
- Medium dogs (10-20kg): 1/2 to 1 garlic clove per day
- Large dogs (20-30kg): 1 to 1+1/2 garlic cloves per day
- Giant dogs: 1+1/2 to 2 garlic cloves per day
Give this dosage of garlic three times a week.
I give garlic to my dogs during spring, summer, and autumn, but some people use it year-round. In case of doubt, consult your Integrative Veterinarian about the best way to include garlic in your dog’s diet.
What About Cats?
As for cats, unfortunately, there are still no studies indicating the safe amount of garlic. Some Integrative Veterinarians only advise giving 1/8 of a garlic clove per day, or even less, three times a week, only during the summer to help repel fleas. Other veterinarians prefer not to recommend garlic for cats at all.
When Is Garlic Contraindicated?
Garlic is safe for dogs when given in the appropriate amounts. However, there are some precautions and contraindications.
Pregnant and Nursing Females
Always be cautious with any medication or supplements in pregnant or nursing dogs. Consult your Integrative Veterinarian before offering garlic to a pregnant dog. Garlic can also alter the taste of breast milk, so it’s best to avoid giving it to nursing females.
Puppies
It is not recommended to give garlic to puppies under 6 months of age. For puppies 6 months to 1 year old, be cautious and only feed half the normal dose.
Akita and Shiba Inu Breeds
These breeds are more sensitive to the hemolytic effects of oxidants like N-propyl disulphide found in garlic. For these breeds, only a much smaller dose than recommended should be given, so consult your Integrative Veterinarian before offering it to these breeds.
Drug Interactions
Garlic can interact with certain types of medication, such as:
- Immunosuppressants
- Heart medications
- Chemotherapy drugs
- Anticoagulants
- Insulin
- Antacids
- Blood pressure medications
If your dog is taking any of these medications, it’s best not to offer garlic.
Before Surgeries
Since garlic can slightly affect blood clotting, discontinue its use at least two weeks before any scheduled surgery.
Sources and References