The stability and dosage of the allicin, a sulfur amino acid present in garlic and partly responsible for its healthy benefits - is important. Allicin is unstable and deterioates within hours at room temperature when the garlic is sliced or cut open. As well, research is now showing that the allicin is actually only one of several key components of garlic which benefit human health. Kyolic, who in 1956 developed an odorless, organic, aged, freeze dried extract of garlic, points out that other regular brands use methods which decrease the potency of garlic, such as heat to distill the oil and dry the powder. The oil is odoriferous without any water soluable compounds, and its labelling may not tell you how much actual garlic oil is present, but rather how much garlic was used initially to make the oil.
Most capsules contain only a bit of garlic oil and then lots of vegetable oil.
Some companies buy this and put it into capsules and tablets. Kyolic has found that the quantity of allicin listed on the label is often unavailable. Finally, the scoop on the aged garlic extract. It is considered to be the most scientifically researched. It is a specific supplement, not a commercial flavoring or additive.