Alpha-lipoic acid is a sulfur-containing compound that naturally occurs in animal organisms and some foods, such as spinach, broccoli, potatoes, and organ meats. In supplement form, it is often produced synthetically for controlled composition and dosing.

Alpha-lipoic acid is found in foods including red meat, organ meats (such as liver), and certain vegetables like spinach and broccoli.

R-ALA refers to one specific form (the R-isomer) of alpha-lipoic acid as it also occurs in organisms. Regular alpha-lipoic acid in supplements is usually a mix of R- and S-isomers, a form widely used for its stability and availability.