Alpha lipoic acid (ALA) is a fatty acid that functions like a vitamin, but it is not classified as such. As a coenzyme, ALA plays an important role in the metabolism of glucose that produces energy in cells. Alpha-Lipoic Acid 300 from Doctor's Best also has antioxidant properties and thus is important for controlling free radicals. Because it is soluble in both water and fat, ALA is sometimes referred to as the "universal antioxidant."