Practically all foods undergo some form of processing before they are ready to eat—from simple processes like cutting and cooking to more complex processes like homogenizing, pasteurizing, fermenting, fortifying, refining, hydrolyzing, and extruding. Processing makes raw foods more palatable, minimizes spoilage, changes texture and flavor, modifies nutrient content, and creates convenience.
The Tufts Health & Nutrition Letter says that some processing, like freezing, pasteurization, vacuum-packing, and (non-alcoholic) fermentation have beneficial effects on health: preserving nutrients, increasing digestibility and availability of some nutrients, or preventing food-borne illness. But in other cases, processing has some negative health effects: partial hydrogenation of fat, for example, creates trans fats that have been linked to increased risk for cardiovascular disease; refining of grains reduces nutrient content and creates rapidly digested concentrated starch which increases risk for weight gain, diabetes, and other negative health effects; and addition of excess salt and sugar is tied to a whole host of illnesses, including cardiovascular disease, diabetes, hypertension, and obesity. Having a clear understanding of these health impacts and what makes a food “processed” is crucial to good dietary decision making.