Web Site of Robert John Morton
Sustainable Food: Our Food Needs
Inputs and Outputs
The human body is a biological machine. As such it needs two main inputs:
It also requires small amounts of other inputs to facilitate control of processes which consume the two main inputs. The body also produces outputs of controlled work, heat and waste material. The way in which the physical inputs and outputs to the human body are classified is illustrated below.
- fuel for energy to sustain its operation
- building material for growth and repair
Carbohydrate is the body's main fuel providing immediate energy. Fat is used to store energy in a stable form. Protein provides the building materials for growth and repair. Vitamins and minerals are the agents and catalysts which facilitate bodily processes. This, however, is an extremely over-simplistic view. For instance, excess protein is also used as fuel. Indeed, if the body is short of carbohydrate, it will use protein as a fuel as first priority before using it for growth and repair. A detailed explanation is available on the web site of the United Nations Food & Agriculture Organisation.
The human body has a complex interrelationship with the terrestrial biosphere. In fact, in isolation, the human body is not a complete functional system. It is only one part of a system, the rest of which is its terrestrial environment. Consequently, there is a large number of other inputs and outputs to the human body. It consumes oxygen and returns carbon dioxide and water. The skin absorbs light to produce vitamins by photo-synthesis. It also sheds skin scales and sweats moisture.
Fortunately the human body is equipped with an excellent control system, which has sufficient built-in negative feed back to give the body a wide tolerance in the amount of each required input. It corrects the amount of each input by passing the excess straight through. Adequate nutrition is achieved, therefore, by ensuring that there is enough of the diet's least available input.
Foodstuffs (things like eggs, milk, meat, vegetables, fruit) between them contain enough of all the things the body needs in proportion to the carbohydrate, protein and fat they contain. In other words, if you get the amounts of those three right using natural foodstuffs, you should by default get an adequate supply of all the other things you need. So provided you are in normal health, all you need do when planning a menu is calculate F(c, p, f) to make sure that the amount of each of these inputs is within the body's window of tolerance.
Different types of individual require different amounts of food according to:
- their stage in life - child, adolescent, adult
- the energy demands of their work or activities
- the type of climate in the place where they live
For the planning of diet, these differences should be taken into account. A food Energy Database could be built from available data from which a program could calculate a person's food needs. The following HTML form should allow anybody, anywhere in the world, to convey enough about himself over the Web to allow such a program to return his required carbohydrate, protein and fat energy needs F(c, p, f) in Megajoules per day. Climate type is posted in the following form automatically from the 'climate' form.
For the purpose of planning food production, it is less complicated to plan for the needs of a generic human. That is, to produce quantities F(c, p, f) from which the quantities F'(c, p, f) needed for any particular type of individual can be provided. This allows the necessary contingency for such things as:
- wastage in getting food from field to table
- depleted yield due to weather or accident
- provision for the visitor, sojourner or wayfarer
- Therefore if
- c = amount (in Mj) of carbohydrate per person per day
- p = amount (in Mj) of protein per person per day
- f = amount (in Mj) of fat per person per day
- n = number of people in family
- then the amount of food a self-supporting family must produce each year for itself is
- E = 365 * n * F(c, p, f)
©Jan 2001 - Robert John Morton