Cooking food tends to break it up, thus preparing it for digestion. Cellulose in vegetables needs loosening and softening, so the nutritious substances associated with it may not be lost, because so fixed in this practically indigestible fiber that the digestive juices of the body do not reach them. Besides the aid of cooking, chopping vegetables fine assists in their digestion as often will treating a vegetable, as spinach, with vinegar. Thorough mastication always increases digestion.

Germs in food are generally destroyed or rendered harmless by cooking. This increases not only the safety of food but also the probability of undisturbed digestion.

Flavors of food are sometimes developed by cooking, but they may also be lost. In cooking vegetables the latter is the usual danger. Those delicately flavored, as cauliflower, cannot be cooked long or in much water. Those with strong juices often need several waters and longer cooking; cabbage may. Vegetables cooked uncut retain flavor that cut they would lose. Cooking-water from vegetables contains many of their nutrients, especially salts, which have dissolved out. It should be used in dressings or soups. This necessitates thorough washing of all vegetables and removal of too strongly flavored parts. Palatability of food is affected by flavor. Digestion is stimulated by palatable food.

Young vegetables require less cooking than old. The difference in starch present partly accounts for this. Starch inadequately cooked makes work for the body by burdening it with undigested food. Thoroughly cooked starch does work for the body by providing it with energy. All vegetables need to be salted as they are cooked. Fresh vegetables require less cooking than wilted. The water lost must be returned in cooking; the toughened fiber must be revived.