What is food?  
  What happens to the food we eat?  
Our nutrient needs  
  Energy balance  
  Nutritional status  
  Laws & labels  
  Additives & colours  
  Toxicity in food  
  Processing food  
  Stability of food nutrients  
  Storage life of foods  
  Food- associated health problems  






- Introduction -


Because health is so closely related to diet, nutritionists and public health workers have sought to identify the optimal diet. The first principle of an optimal diet is to ensure that the amount of food is right -- not too little and not too much. If a person's growth has proceeded satisfactorily and weight is appropriate, this particular goal is realized.

The second nutritional principle is to have as wide a variety of foods as possible. The greater the variety of foods you eat, the more likely you are to obtain the full range of nutrients required. Traditionally, and for most of human experience, as hunter-gatherers, people collected fruits, nuts, seeds, leaves, roots, caught small animals and fish, and hunted, with less success, larger game. This is the diet with which humans evolved; our bodies are designed to be serviced by the nutrients in such a diet. Another reason for emphasizing the importance of variety from a range of biological sources of food is that, if there is any toxic or harmful factor in a particular food, it will tend to be diluted to a level where it is not hazardous. The advent of food staples -- such as potatoes, wheat and rice - is more a reflection of agricultural practice and a way of feeding a larger number of people at a lower cost than of nutritional principle. Insofar as a staple is often unavoidable, it is best to have it unrefined so that as many nutrients as possible are consumed.

The third nutritional principle, related to the first, is to balance food intake with the rate our bodies use it up. In our society the balance is often not achieved, because our level of physical activityFind out more about this term is so much less than that of our hunter-gatherer forbears. Important concepts nutritionists use in finding what the balance should be are 'energy density' and 'nutrient density'. The average person, with an average level of physical activity, needs a certain minimum of energy every day -- not less than 1200 kilocalories" (about 5000 kilojoules) per day. The more energy (kilojoules or kilocalories) there is per unit (weight or volume) of a food, the more 'energy dense' it is. The more nutrients there are for a particular amount of energy, the more 'nutrient dense' it is. Fatty foods are generally the most energy dense. Some are also nutrient poor, like butter and lard. Vegetables tend to be low in energy density and high in nutrient density. The less physically active we are, the less can we have energy-dense foods and the more we should have nutrient-dense foods.

Dietary guidelines

The pattern of disease in affluentFind out more about this term society - obesity, vascular disease, cancers, diabetes, etc. -- is associated with a high intake of fatty meat and dairy products, a high intake of alcohol, a low intake of wholegrain cereals, fruits and vegetables, and a high intake of sodium (especially as salt). It is for these reasons that several countries have now developed dietary guidelines similar to the following:

    • eat a variety of foods each day
    • encourage breast feeding
    • prevent and control obesity
    • decrease total fat intake
    • decrease consumption of sugar
    • limit alcohol consumption
    • increase consumption of cereals, fruits and vegetables
    • reduce sodium intake
    • encourage water intake.

Eat much more fruit, vegetables and complex carbohydratesEncouragement of breast feeding is included in recognition of breast milk's unique properties, such as those protecting against infection, which cannot as yet be reproduced in infant milk formulas.

Eat meat, beverages and seafood in moderationAverage life expectancy in the twentieth century has increased. Yet among developed countries there is a hierarchy of life expectancy with, for example, Sweden, Greece and Japan being ahead of the United Kingdom, Australia, New Zealand and the United States. To some extent, these differences appear to relate to food intake pattern. It seems that much may be gained from analysing why this is so, identifying an optimal diet and following guidelines that promote it.

Food is not the only factor that can influence health; most health problems in modern society are 'multifactorial' in origin. But nutrition is clearly a very important factor. If you can establish healthy dietary habits in conjunction with attention to other factors (such as physical activity, smoking, stress, work environment), you will give yourself the best chance against ill health and for a long and active life.


*The amount of energy released from the food we eat is measured in units called kilocalories or sometimes Calories spelt with a capital C. Another unit of energy commonly used is the kilojoule. It is easy to convert kilojoules to kilocalories and vice versa:

1 kilocalorie = 1 Calorie
1 kilocalorie = 4.2 kilojoules (approximately 4)
1 kilojoule = 0.24 kilocalories (approximately 1/4)
1 megajoule = 1000 kilojoules

Food Facts
- Why you need this book
- Why nutrition is important
The optimal way of eating

Also on this page:

-  Dietary Guidelines

-  Footnote:
   calories and joules