The manner in which foods are cooked alters their digestibility. Cabbage, for example, cooked in one way is easily digested; cooked in another manner is almost indigestible.
Much of the indigestibility of cooked foods results not so much from the cooking, per se, as from the mixtures that are jumbled together to cook. Take the Southern practice of cooking beans, greens, cabbage, etc., with a large piece of fat, salt bacon, as an example of concocting indigestible mixtures; or the method of frying potatoes (starches) in fat.
The waterless cooker is the best cooker that has been devised. This should not be confused with the pressure cooker. Rapidly growing in popularity, this expensive and dangerous (they sometimes explode) pressure cooker is the worst cooker ever invented. Cooking foods under high pressure rapidly destroys their vitamins. The old fireless cooker that cooked foods at a low temperature over a long period, was a very destructive cooker. Frying pans and boilers are among the worst cooking utensils. Several different types of waterless cooker are available. The reader may choose his own. I have no prejudices against the aluminum cookers, but if the reader is afraid of this form of cooker, the stainless steel cooker is very efficient.