Alliin is primarily known for its role as a precursor to allicin, a compound responsible for the characteristic odor and many of the health benefits of garlic. When garlic is crushed or chopped, the enzyme alliinase converts alliin into allicin, which exhibits strong antimicrobial, antifungal, and antiviral properties. This transformation makes alliin a key compound in natural defense mechanisms of the garlic plant and a focus in dietary supplements aimed at supporting immune health.

In nutritional and pharmaceutical applications, alliin is used in standardized garlic extracts to ensure consistent bioactive content. These supplements are commonly marketed for cardiovascular support, as alliin contributes to effects such as mild blood pressure reduction and inhibition of platelet aggregation. Research also suggests potential anticancer properties, with studies exploring its role in reducing the risk of certain cancers due to antioxidant and cell-protective activities.

Due to its stability compared to allicin, alliin is preferred in supplement formulation. It is often enteric-coated to prevent degradation in the stomach, ensuring delivery to the intestine where it can be enzymatically activated. Additionally, alliin is used in research settings to study sulfur-containing compounds and their metabolic pathways in humans and animals.