I give a little Garlic to my two 75 lbs dogs for Summer with no problem. Garlic got its bad reputation following a study done in Japan back in 2000. They only used 4 dogs for the study and they concluded that it could give them Heinz body anemia. But... the amount of Garlic administered was very, very high, and besides, the dogs were not sick from it. So, just like the BSL scare, people started panicking about Garlic. I mean, a lot of people. There are so many other studies in favor of Garlic, I have yet to find another one that proves Garlic is not good for dogs. I plan on contacting local vets and asking them if they have ever encountered a dog who got sick from ingesting Garlic.
If you know of another study that shows facts about Garlic being no good for dogs, I would appreciate you sharing with me. In the meantime here are some information I found about Garlic; links are provided for your convenience.
Garlic has long been used as a safe medicinal plant in holistic medicine for people and pets as well. However, recently, the safety of Garlic on dogs (and cats) has come under close scrutiny due to its properties as a member of the Allium Genus, a branch of the Lily family, along with onions and shallots.
A compound found in onions (and in lesser amount in Garlic) called 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 on a regular basis, the process can lead to Heinz-body anemia and even death.
Does that mean Garlic is unsafe for dogs? Not quite. They key to safe use of Garlic on dogs is the dosage level and frequency of use. For a dog to develop Heinz-body anemia, he would have to eat over 0.5% of his body weight in onions to even begin the oxidative process. It means a healthy 60-pound dog would have to eat a whole 5 oz onion, or several cloves of Garlic, to start the Heinz-body process. Since red blood cells are constantly regenerated from the bone marrow, a dog would likely need to ingest this much amount of onion or Garlic on a repeated basis to cause permanent harm.
GARLIC FOR DOGS - HOW MUCH AND HOW OFTEN?
According to Gregory Tilford, (author of "All You Ever Wanted to Know About Herbs for Pets"), dogs can quite saferly consume 1/8 teaspoon of Garlic powder per pound of food 3 to 4 times a week. Dr. Martin Goldstein (author of "The Nature of Animal Healing") recommends adding Garlic to home-made pet food and he himself feeds Garlic to his own cats and dogs on a regular basis. Dr. Pitcairn (author of "The Complete Guide to Natural Health for Dogs and Cats") recommends the following amount of fresh Garlic for dogs, according to their size:
10 to 15 pounds: half a clove
20 to 40 pounds: 1 clove
45 to 70 pounds: 2 cloves
75 to 90 pounds: 2 1/2 cloves
100 pounds and over: 3 cloves
"One of the benefits of Garlic, especially in combination with Brewer's Yeast, is repelling fleas and ticks."
WHO SHOULD NOT BE GIVEN GARLIC?
Garlic should NOT be fed to pets with a pre-existing anemic condition or to those scheduled for surgery. Also, young puppies before six to eight weeks of age should NOT be given Garlic because they do not begin reproducing new blood cells until after 6-8 weeks.
In addition, since Garlic stimulates the immune system, people with Lupus (which is an autoimmune disease) are advised not to eat Garlic by the Johns Hopkins Lupus Center. Although I haven't found any reports or research on dogs with Lupus and Garlic consumption, I think it would NOT be a good idea to give Garlic to dogs with Lupus or other autoimmune diseases since it would work in the same way in dogs as in humans (i.e. stimulate the dog's aready over-active immune system). Click here for source and more info
It all started over 100 years ago, when wild onions (in the same family as Garlic) were fed to cattle, sheep and horses and these animals showed toxicity symptoms. In the 1930s, studies showed that dogs that ate onions showed toxicity symptoms. Fast forward to the 1980s, cats that ate onions exhibited the same toxicity symptoms as dogs did. It is important to note that cats are six to eight times more sensitive to onions than dogs.
Garlic got a bad reputation in 2000, when a research paper was published that was based on Garlic's effect on dogs. Even though the dogs tested did not show any outward appearance of toxicity symptoms, there was an effect on the red blood cells. The researchers stated: "We believe that foods containing Garlic should be avoided for use in dogs." This study, which was undertaken at Hokkaido University, was conducted on four dogs, giving each one 1.25 ml of Garlic extract per kilogram of body weight for seven straight days.
As an example, if the dog weighed 40 pounds, it would be given about 20 cloves of Garlic - a staggering amount! Using this amount of Garlic, the study concluded that Garlic had the "potential" to cause Hemolytic Anemia (damage to the red blood cells), and so Garlic should not be fed to dogs. It is important to note that even at these highly elevated doses, no dogs on the study developed Hemolytic Anemia. See the study here