Our daily bread
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In a general consideration of humanity’s food prospects we may recognize four biological systems: Croplands, Grasslands, Forests and Oceanic Fisheries. In that these are biologically renewable resources they form a foundation to the global economic system. It is essentially to croplands that humanity must look for future increases in food supply, particularly in the three staple cereals (wheat, rice and maize) to which over half the world’s cultivated land is devoted and which constitute the largest proportion of plant foods produced. All plants foods combined provide an estimated 88 per cent of the calories (carbohydrates and fats) and 80 per cent of the protein that .human beings consume on a global basis and the balance is derived from animal products (Chrispeels and Sadava, 1977). This situation applies particularly to the underdeveloped countries, in contrast to the affluent countries of North America, and to some extent Europe, where more or less half of the protein consumed may come from animal products. When any one of the grains is consumed as a single staple it is likely to lead to protein malnutrition because grains are generally deficient in one or two of the amino acids essential for growth and health.