When reheated, especially in dishes which are cooled gradually or kept heat for quite a while, these nitrates can change into nitrites, and after that likely into nitrosamines, that may be carcinogenic. Ideal follow: Consume dishes with cooked spinach or leafy greens new. Leftover Gravy and Pan Drippings (picture credits: https://derrickv639zbd7.59bloggers.com/profile