Indian pickles are made with mustard oil, which has a sharp, pungent flavor. However, the U.S. Food and Drug Administration requires mustard oil sold in the United States to be labeled as being "for external use only" because it has a high erucic acid content. There is some concern that erucic acid can elevate the risk of heart disease, although other sources say that is not a conclusive finding. There is now a food grade mustard seed oil available, which is sourced from seeds that are bred to reduce the erucic acid content. Ultimately it is up to you whether or not you want to use mustard oil in this pickle or any other recipe. Mustard oil is used widely in India, and I use it in just a handful of dishes where it makes a big difference to the flavor. I buy mustard oil at the Indian grocery store and I have occasionally bought this brand online, on Amazon.