Garlic in appropriate amounts is perfectly fine for dogs. Like many things, garlic in large amounts can certainly lead to toxicity, but the amounts we add to our food are well below levels that can cause issues and is very safe and beneficial.
When it comes to the controversy regarding garlic, this is because it belongs to the Allium family and it contains a substance called thiosulphate, the ingestion of which has been known to be harmful to dogs. The key though, is in the quantity required to do any harm. In fact, there have been studies that show that a 34 kg Labrador would need to eat five full heads of garlic or about 75 cloves of garlic in each meal before there would be any adverse effect on the red blood cells. Similarly, a dog weighing a mere 4.5kg would need to eat 25 grams of garlic – about half an entire head of garlic, or about 6 to 8 garlic cloves in every meal to experience any adverse effects.
Dogs Naturally Magazine has an interesting article on this topic for further reading here.
For more information on garlic and the other super-foods visit, “Clean eating and super-foods for dogs”.