Apart from fruits and some vegetables, most raw ingredients (e.g. grains and dried pulses) need to be processed and/or cooked in some way to make them edible, and in some cases to ensure they are safe to eat (e.g. pasteurization of milk, cooking of eggs, meat and fish), and/or preserve them by freezing or canning.

Most of us don’t have the inclination or time to cook every meal from scratch and modern lifestyles have been enabled by an array of processed foods, recognized for their convenience and palatability. Yet, the healthiness of some is also under scrutiny.

Processing methods such as cooking, fermentation, drying, salting and smoking are not new, and developed in domestic kitchens.

Dietary guidelines

Foods that now feature in dietary guidelines around the world because of their contribution to essential nutrients, such as ready-to-eat wholemeal bread and high fibre breakfast cereals, or wholemeal pasta and pasteurized milk are nevertheless processed foods.

But the elephant in the room is that not all processed foods are equal. Some processes are important from a safety perspective, such as heat treatment of nutrient-rich foods to reduce microbial activity and minimize health risk, whereas others might be considered more cosmetic or are associated with foods that have a relatively poor nutrient profile. 

According to a review by Sadler and colleagues, current food classification systems for processed foods lack consistency and consensus, often leading to confusion and debate even among scientists.