There is plenty of information and misinformation available on the internet about the use of garlic in food and supplements for dogs and cats. Garlic has many health enhancing effects such as aiding digestion, eliminating internal and external parasites, stimulating immune functions and increasing killer cell activity, lowering blood cholesterol and triglyceride levels, and acting as a a tonic for the cardiovascular system. Fresh garlic also has powerful antibacterial and antifungal properties. It has been used for thousands of years in Chinese and Ayurvedic medicine. Holistic veterinarians have been recommending garlic for many years for its multiple health benefits.
Garlic's impact on health has come into question recently due to its properties as a member of the lily family, along with onions and shallots. A compound found in onions, n-propyldisulfide, can – in large doses – cause oxidative damage to red blood cells, creating Heinz bodies and triggering the body to reject these cells from the bloodstream. If large doses of this compound are ingested frequently enough, the process can lead to anemia and even death. The dosage level and frequency of consuming the offending compound are the key here. Typically an animal would need to ingest over 0.5 % of it’s body weight in onions (a 5 ounce onion for a 60 lb. dog) to even begin the oxidative process. Since red blood cells are constantly regenerated from the bone marrow, a dog would likely need to ingest this much onion on a repeated basis to cause permanent harm. Garlic contains less of the n-propyldisulfide compound than onions do.
In The Nature of Animal Healing, Dr. Martin Goldstein recommends adding garlic to home-made pet food and, in fact, feeds garlic to his own cats and dogs on a regular basis. According to Gregory Tilford in Herbs for Pets: The Natural Way to Enhance Your Pet's Life, dogs can quite safely consume 1/8 teaspoon of garlic powder per pound of food 3-4 times per week. Cats probably should be given a bit less, as they are more sensitive to the compounds in garlic. Tilford cautions cat guardians to watch for behavioral changes or digestive upset, and to listen to the cat if she rejects food or supplements containing garlic. Fresh garlic is less concentrated than dried garlic. In Dr. Pitcairn's Complete Guide to Natural Health for Dogs & Cats, Dr. Richard Pitcairn recommends up to ¼ clove of garlic per day for cats and ½ to 3 cloves for dogs. As with most herbs, at least one day off per week or a periodic week off from garlic is a good idea.
"Garlic has many health enhancing effects such as aiding digestion, eliminating internal and external parasites, stimulating immune functions and increasing killer cell activity, lowering blood cholesterol and triglyceride levels, and acting as a a tonic for the cardiovascular system."
The key in feeding or supplementing with garlic is moderation and common sense. Using garlic and brewer’s yeast tablets during flea season has long been a common practice among savvy pet owners to help make pets less attractive to fleas. Using garlic in the diet or as a supplement for any of its health benefits is not likely to cause problems for healthy dogs and cats. Obviously, any animal that has a pre-existing anemic condition should not receive garlic. Puppies under 8 weeks of age should also not be given garlic, as they do not begin reproducing new blood cells until after 6-8 weeks of age.
The ASPCA Animal Poison Control Center is the best resource for any animal poison-related emergency, 24 hours a day, 365 days a year, and their certified vets recommend:
“Garlic is commonly found in pet food and is okay for consumption in small, limited doses. Ingestion of garlic and onions, whether raw or cooked, may be potentially toxic causing signs ranging from vomiting and diarrhea to circulatory issues. The toxicity is based on the amount ingested and the size of the pet. Cats are more sensitive to dogs, so if you have feline don't let them eat from your dog's food bowl.”