While most people eat enough calories they are often from the wrong foods. For example, fatty or sugary foods are low in vitamins and minerals from processing, and this is why many experts believe the typical modern Western diet allows disease to develop, if it does not actively promote it.

Furthermore, even a diet rich in fresh, unprocessed foods can be deficient in micro nutrients, for intensive farming methods have largely robbed the soil of nutrients. A mineral-rich vegetable, for instance, cannot be produced from soil that is empty of minerals. Fruits and vegetables are force-grown and ripened; by the time they reach our supermarket shelves, there is little or no nutrition in them.

Other factors can also increase the need for vitamins, and minerals. Examples are poor digestion and absorption, smoking, and drinking. Rapid growth in childhood and adolescence, pregnancy, lactation, and old age, all increase the need for nutrients. Requirements are also raised during illness, when we are under stress, taking drugs, or affected by environmental toxins and pollutants. It is in these situations that nutrients such as vitamins, minerals, amino acids, and essential fatty acids may be recommended and prescribed.