When looking at human diet the normal focus is whether people are getting sufficient food, and whether their diet avoids such diseases as diabetes.
The modern “western” diet is reliant on plant materials (including the food of animals we kill for meat) which are deficient nutritionally, compared with 60 years ago. Levels of key minerals including magnesium, selenium, copper, calcium, zinc, iron have fallen. As Welch and Graham  said, “The consequences of food system failures include lethargic national development efforts, continued high population growth rates, and a vicious cycle of poverty for massive numbers of underprivileged people in all nations. Our food systems are failing us globally by not providing enough balanced nutrient output to meet all the nutritional needs of every person, especially resource-poor women, infants and children in developing countries.” This shortage of key minerals and vitamins, is known as micronutrient malnutrition, or “hidden hunger”.
According to the WHO/UNICEF more than 2 billion people may be affected by micronutrient malnutrition, in particular vitamin A deficiency, iron deficiency (anaemia), and iodine deficiency. Susan Long reported on a study on the use of biofortified, iron-rich rice, which held promise, as a rice diet is normally low in iron. Welch and Graham  suggest that one of the causes of micronutrient malnutrition has been the displacement of traditional crops such as pulses, reducing the availability of micronutrient-rich plants foods. They argue for a “food systems paradigm” which takes into account the specific nutrient requirements of people, rather than focusing on the quantities of food produced.
There appear to be two main processes by which human diet has been adulterated (given that there is an adequate food supply in the first place), the first is by “processing” food which is an effective way of removing essential vitamins and minerals, white rice, white sugar and white flour are the obvious targets, but the second process is by the depletion of minerals in top soil and the destruction of the microbes in the soil. As a result soils are often deficit in key minerals, including magnesium, selenium, copper, calcium, zinc, and iron. Minerals perform essential functions in the operations of our cells, and mineral additives added to our diet are not as effective as those found in foods, as they do not exist in a “food state”, and are not easily absorbed during the process of digestion. According to The Merck Index, the composition of chemical-based Vitamin B-1 is coal tar derivatives, hydrochloric acid; acetonitrole with ammonia, Vitamin B-12 is cobalamins reacted with cyanide, Vitamin E is trimethylhydroquinone with isophytol; refined oils, Vitamin C is hydrogenated sugar processed with acetone and Vitamin D is irradiated animal fat/cattle brains or solvent extracted, other chemical “vitamins” are similar concoctions. We actually need these vitamins and minerals to be present naturally in our food, chemicals are not an adequate replacement, as our bodies can only effectively absorb nutrients in a “food state”.
Zinc is one example of an essential mineral, Harold H. Sandstead, noted that it, “plays a fundamental role in expression of the genetic potential.”  Copper is another essential mineral, and R Uauy, M Olivares, and M Gonzalez found that, “New biochemical and crystallographic evidence define copper as being necessary for structural and catalytic properties of cuproenzymes.” They added, “Diets in Western countries provide copper below or in the low range of the estimated safe and adequate daily dietary intake.” 
As scientists look at the actual dietary requirements of the human population, in order to create a more sustainable and productive agricultural system, they will need to have the health of the population as their primary concern. We live in a world in which everything is connected, and health is strongly related to diet. Zinc and copper, in food forms (not in the pure mineral form) are only examples of key nutrients so often absent from modern diets, and ultimately people are therefore less able to fight disease, or even develop to their full potential, because of the impact of micronutrient malnutrition.
 Ross M Welch & Robin D Graham – ‘A New Paradigm for World Agriculture: meeting human needs: Productive, sustainable, nutritious”, Field Crops Research Volume 60, Issues 1–2, 1 January 1999, Pages 1–10
 FAO – “Preventing Micronutrient malnutrition a guide to food-based approaches”, International Life Sciences Institute, Washington, DC, 1997 – introduction
 Susan S Lang – “Biofortified, iron-rich rice improves the nutrition of women”, Cornell University News Service 29 Nov. 2005
 Ross M Walch and Robin D Graham – “A New Paradigm for World Agriculture: meeting human needs” in Field Crops Research 60 (1999) pp 1-10
 David R Montgomery – “Dirt, The Erosion of Civilizations”, University of California Press, Berkeley, Los Angles and London, 2007, pages 16-17
 The Merck Index, Fourteenth Edition, Maryadele J. O’Neil, editor, Merck, Whitehouse Station, New Jersey, USA, 2006