Introduction to Human Nutrition

We have heard the terms food, nutrients and nutrition and; nutritionists, dieticians often advise us to consume a balanced diet. But what do these concepts/terms mean?
Food
Food can be defined as any solid or liquid material which when eaten provides nutrients to the body. A wide range of foods are available in our communities such as e.g. peas, beans, meat, chicken, fish, matooke, cassava and vegetables e.g. cabbage, spinach etc.
Nutrients
Nutrients are the chemical substances found in food; that are extracted from food as it passes through our digestive system and are used by the body to perform various functions.
Nutrients can be divided into two broad categories: MACRO nutrients and MICRO nutrients.

• Macronutrients are required by the body in relatively large amounts; they include carbohydrates, proteins and fat.

• Micronutrients are required in relatively smaller amounts by the body; they include vitamins and minerals.

In order for our body to function properly, a combination of both macro and micro nutrients is required in the right amounts and combinations.
Classification of food into different food groups
Foods contain a variety of nutrients in different quantities, however a food can be classified into a particular food group depending on the predominant (major) nutrient it contains. According to this classification we have the following food groups:

1. Energy giving foods/GO foods
2. Body building foods/GROW foods
3. Protective foods/GLOW foods

1. Energy giving foods/GO foods

Energy giving foods/GO foods are those rich in food nutrients called carbohydrates. We obtain carbohydrates through eating plant-based foods. The main examples of carbohydrate containing foods include: millet, sweet potatoes, cassava, plantain (matooke), irish potatoes sorghum, yams, rice, and bread.
Fats and oils are also another source of energy but also essential for absorption and utilization of fat-soluble vitamins. However, fats and oils should be consumed in moderation as excessive consumption can contribute to making individuals overweight or obese and put them at risk of developing certain diseases such as coronary heart disease, high blood pressure and certain types of cancers.

2. Body building foods or GROW foods

Body building foods or GROW foods are those rich in food nutrients called proteins. They are essential for growth, boosting body immunity and formation of the body tissues such as muscles, skin and nails.
Body building foods or Grow foods come can be obtained from two major sources:

• Animal-based foods and related products such as fish, meat, poultry, eggs, milk and yoghurt.
• Plant-based foods and related products such as beans, peas, groundnuts and soy. 

3. Protective foods/GLOW foods

Protective foods or GLOW foods are those foods rich in vitamins and minerals. Vitamins and minerals are required by the body for normal physiological functions such as to strengthen the immune system and for facilitating a range of other bodily functions.
Protective foods include:
Vegetables
In addition to providing vitamins and minerals, vegetables add taste, flavour and colour to our meals. Common vegetables include: amaranthus (dodo), spinach, kale (sukuma wiki), carrots, onions, green pepper. 
Fruits
Fruits are also a rich source of several vitamins and minerals. For example: pineapple, passion fruit, avocado, mangoes, pawpaws, oranges and other citrus fruits. However, the deep yellow or orange coloured fruits are richer in vitamins, particularly vitamin A.
Water
Water is not a food group but is essential for the human body to function properly, for example: enabling body processes to take place such as digestion and transporting nutrients around the body.
Nutrition
The term ‘nutrition’ broadly covers all processes by which living organisms take in and use food for the maintenance of life, growth, and the functioning of organs and tissues. It further describes what different foods are made of (i.e. nutrients) and the processes through which our bodies make use of the nutrients to enable us to perform various activities.
Balanced diet
A diet is the pattern of foods eaten; the normal or habitual intake of food of an individual or population. Therefore, a balanced diet is one that provides all the nutrients in their correct proportions as required by the body.
Attaining a balanced diet requires that one makes careful food choices from different food groups and has a diverse diet, i.e. eats a variety of foods in a day. It is also very important that the food consumed caters for body’s nutrient needs/requirements.

Definition of other key concepts in Human Nutrition
Nutritional status: the condition of the body in those respects influenced by the diet; the levels of nutrients in the body and the ability of those levels to maintain normal metabolic integrity.
Requirement: minimum amount of a nutrient needed to sustain a physiological state, function, or structure in an individual.
Recommendation: normalized estimate of nutrient needed to cover most individuals in a population group.
Guideline: advice on diet composition to population groups, aimed at maintaining health and preventing diseases.
Recommended Dietary Allowance (RDA): levels of intake of essential nutrients considered on the basis of available scientific knowledge, to be adequate to meet the known nutritional needs of individuals.
 
Suggested further reading materials:
Glyman, C. A., & Biser, D. (1992). Learning your ABC's of nutrition. Lake Forest, Ill.: Forest House Pub. Co.
Gibney, M.J, Lanham-New, S.A, Cassidy A & Vorster H. H. (eds) (2009). Introduction to Human Nutrition. 2nd Edition. West Sussex: Wiley-Blackwell.
Geissler, C. & powers, H. J. (2011). Human Nutrition, Edinburgh, Churchill Livingstone Elsevier.

Suggested weblinks:
Human nutrition in the developing world.
See link: http://www.fao.org/docrep/w0073e/w0073e00.htm

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