The advertising managers for breakfast cereals probably don't want us to think this way, but these cereals represent a modern take on the oldest of all human diets. In the UK, people probably still think vaguely of a proper meal as being “meat and two veg”, even if they rarely cook such a meal. Yet in global and historical terms, such a diet is highly atypical. The majority of traditional cuisine consisted of a large quantity of a plant-based staple component plus a smaller amount of what is called a taste component. That is the exact converse of meat-and-two-veg, or its more modern incarnation as beefburger and chips, where the taste component dominates and the staple is reduced to an accompaniment. The traditional staple, in temperate areas, was almost invariably made from a cereal crop, wheat, oats, maize or barley. Think of bread, mainly made from wheat, porridge/porage from oats or tortillas and other flat breads from maize. Potatoes are the only other major staple of the temperate regions. In warmer areas, the staple is rice, eaten boiled or fried.
Together, the cereals have dominated human nutrition since our earliest ancestors foraged for the large seeds of different grass species in Africa and the Middle East. Our dietary system and preferences probably evolved hand-in-hand with these grasses, ensuring their dominant position in human nutrition. Cereals supply a good mixture of starch, the carbohydrate that provides a source of food energy, dietary fibre that contributes to gut function and other physiological needs and a useful amount of protein. The major limitation of cereals in nutritional terms is the nature of this protein, which is low in an important essential amino acid called lysine which we cannot synthesise in our bodies. To grow and remain healthy, we therefore have to eat foods that contain this component. This is where the taste component of traditional diets comes in. Meat proteins contain lysine, so by supplementing the basic cereal component with a small amount of meat, humans were able to obtain all the nutrients they needed. Over many generations, our sense of taste probably evolved so that we found the cereals rather bland and so we deliberately sought out other dietary materials to satisfy ourselves. In the process, we obtained a good dietary mix of nutrients. The animals our ancestors hunted were often ruminants, which unlike ourselves are able to digest the cellulose of grass and other leaves, so indirectly they enabled us to make use of the entirety of our grassy surroundings.
A strange evolutionary quirk means that for some humans, certain proteins found in wheat, and to a lesser extent in barley and oats, cause damage to the digestive tract in the form of coeliac disease. But for the majority, cereal plus taste is what we need. The taste component doesn't have to be meat, although meat is one of the best sources of lysine and of some other micronutrients. The protein of many legume seeds (peas, beans etc.) has pretty good levels of lysine, so the maize-plus-beans diet traditional in Central America offers another good mixture. What the breakfast cereal manufacturers of today are doing is producing a “staple plus taste” diet in a form that is convenient for modern lifestyles. While their intent is undoubtedly more financial than nutritional (except when it helps the marketing pitch) their products do fit the classical model very well, and so provide a good dietary base for most people. Millennia of selection of cereal plants by humans has resulted in a crop that puts a larger percentage of its growth into the grain, so cereals also provide a very efficient means of obtaining food energy from land. Modern plant breeding has taken this process even further, increasing the harvest index (the ratio of grain to supporting stems and leaves) to over 50 per cent. This has the incidental advantage that the shortened straw is stronger, so the crop is less susceptible to damage by bad weather. This allows the crop to make use of fertiliser nitrogen effectively, increasing the yield obtainable.
Worldwide, rice is the single most important cereal, able to grow in both dry and wet regions. It has supported the Chinese population over centuries, using highly sophisticated terracing and flooding techniques to grow sometimes two crops of rice a year. This has allowed the Chinese population to be grow to its present size, despite the fact that only a relatively small proportion of China's land surface is appropriate for cultivation. The story of Chinese food, the way it is changing now and the implications of this for all our futures is analysed in Block 5 of U116, Environment; journeys through a changing world. For the majority in China, their diet used to be almost exclusively vegetable-based, with rice supplying the staple and a range of vegetables supplying the taste and essential nutrients missing from the rice. But modern, urban China has developed a taste for the high-meat-content diets of Europe and the USA. The implications of this for global nutrition are interesting; while some meat is an extremely useful component of diet, high levels of consumption increase the land area needed, because the conversion of grass or cereal to meat is less efficient than direct consumption of cereals. This is not to say that meat should not be eaten – there are areas of land that can only support grazing livestock, and other livestock can make use of waste foods that we humans reject. But in the longer term, it is possible that our meat consumption will have to decline, and the breakfast cereal could be the model for the general diet. I wonder how long it will be before we are offered the cereal bar with a small amount of added meat? It would have all the convenience we crave, and would be a very efficient use of raw materials.