The vital substances necessary to the body are referred to as essential as in essential amino acids and essential fatty acids. Essential means cannot be made by the body and MUST come from the diet.

Food n. that which is eaten to sustain life, provide energy, and promote the growth and repair of tissues; nourishment [Old English fōda, nourishment ]

According to this definition, a lot of people are living on something other than food.

Will this substance ADD more life, more health, and will it nourish and repair my tissues, or will it reduce my health?
The question now becomes, how do we classify or know which foods are really foods and which are non-foods? What substances are essential to life? What substances can we not live without? What is the body made out of, which if missing will create illness?
The vital substances necessary to the body are referred to as essential as in essential amino acids and essential fatty acids. Essential means cannot be made by the body and MUST come from the diet. Amino acids, for example, are the building blocks that make our hair, nails, eyes, muscles, joints, etc. Fatty acids make up the outer and inner structures of our cells, not to mention our brains, nerves and hormones.
There are many nutrients that if missing from the body will cause disease. These essential raw materials must also include vitamins and minerals. And enzymes must be added to this list because consuming foods that are void of enzymes can create degenerative diseases. Enzymes are the things that do the work of the body, similar to assembly workers in a factory.
Foodstuffs that contain all of these nutrients are more food than those that leave out these factors or contain them but in a destroyed or altered form, as happens when food is cooked, pasteurized, processed or roasted. Simply stated, foods containing all these factors amino acids, fatty acids, vitamins, minerals and enzymes and in an optimum balance would create the most health. This is why isolated food factors such as those in protein shakes (isolated soy protein), synthetic vitamins (petroleum derivatives), refined sugars and carbohydrates (which have to be enriched with synthetic vitamins because they are depleted) are more nonfoods that anything else. So, we have a scale from healing foods to illness-creating nonfoods. This diet stresses the importance of consuming foods that naturally contain all five building blocks. (from the 7 Principles of Fat Burning Dr. Eric Berg)