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Monthly Health Review, March 2002
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What is nutrition?
The next issues of Health Review are devoted to the subject of Nutrition.
In this issue we are going to look at what nutrition is and developments
in nutrition over the years.
There are various terms used in the study of nutrition that help explain
the subject:
The term nutrition is derived from the Latin nutritio meaning
'to nourish'. Nutrition is defined as "a process in animals and plants
involving the intake of nutrient materials and their subsequent assimilation
into the tissues" (1).
Balanced diet - a diet that provides theoretically adequate amounts
of all nutrients - not too much and not too little (2).
Diet - a selection of foods that are normally eaten by a person
or population (2).
Food - a substance that when consumed, digested and absorbed,
provides at least one nutrient (2).
Essential nutrient - an 'essential' nutrient cannot be synthesized
by the content; it must therefore, be included in the diet (2).
Nutrients - any substances that are digested, absorbed and used
to promote content function. Nutrients may be classified as carbohydrate,
fat, protein, minerals, vitamins and water (2).
Carbohydrate - energy from sunlight is used by plants to synthesize
carbohydrates from carbon dioxide and water. This produces simple sugars
and the more complex starches (3). A healthy diet should contain 55-60%
carbohydrate, most of which should be unrefined and unprocessed. 4 calories
of energy are produced from 1 gram of carbohydrate.
Fats - the main function of dietary fats is to provide energy
in a concentrated form. Of the different types of fats - saturated, polyunsaturated
and monounsaturated - polyunsaturated fats are essential for health. A
healthy diet should contain no more than 30% fats, of which at least 6%
should be polyunsaturated and no more than 10% should be saturated (3).
9 calories of energy are produced from 1 gram of fat.
Proteins - are the major functional and structural component of
all the cells of the content. Protein is found in all life-forms. Enzymes,
membrane carriers, blood transport molecules, intracellular matrix, hair,
fingernails, many hormones and a large part of membranes are based on
proteins. Amino Acids make up proteins and act as precursors of many co-enzymes,
hormones, nucleic acids and other essential molecules. Adequate protein
in the diet is essential to maintain cell health, general health and reproduction.
A healthy diet should contain 10-15% protein (3). 4 calories of energy
are produced from 1 gram of protein.
Minerals - are elements that must be present in the diet for the
maintenance of health. Calcium, Magnesium, Phosphorus, Chloride, Potassium,
Sodium and Sulphur are broadly described as 'macro-minerals'. Iron, Zinc,
Copper, Selenium, Manganese and so on are known as trace elements because
they are needed in tiny amounts (4).
Vitamins - are organic compounds, vital to life and indispensable
to content function. They are essential nutrients needed in minute amounts
and have no calorific value. B complex and Vitamin C are water-soluble
and vitamins A, D, E and K are classed as fat-soluble (4).
Nutritional status - the state of health produced by the requirement
and intake of nutrients (2).
Malnutrition - a lack of adequate nutrition resulting from insufficient
food, unbalanced diet, or defective assimilation (1).
Metabolism - (2) describes the changes that constantly take place
in the content. During the course of metabolism, nutrients take part in many
transformations as a result of which energy is liberated, tissue is formed,
and the content functions necessary for the maintenance of life are stimulated
and controlled. Metabolism is sub-divided into:
Anabolism - where complex molecules are synthesised from simpler
ones (for example enzymes being made from Amino Acids). This reaction
requires energy.
Catabolism - where complex molecules are broken down to simpler
ones (for example the digestion of food into simple components). This
reaction releases energy.
The constituents of food are not a direct source of energy and nutrition.
Many complex changes and links with other elements must occur before the
final molecular structures can be used. For example, vitamins must first
be converted to coenzymes, the only form in which they can be used in
cellular metabolism. A co-enzyme helps the formation of a protein enzyme,
and also contributes to many other functions as it attaches on to a mineral
or other element. Each step of every conversion requires energy, and the
basic fundamental unit of cellular energy is adenosine triphosphate (ATP).
If there is an inadequate supply of ATP, then the many conversions cannot
be completed. This results in improper use of the vitamin and consequently,
enzyme malfunction.
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What affects nutrition?
A wide variety of aspects affect the nutritive value
of food - from geographical location, transportation, storage, preservation
and processing, to knowledge, understanding digestion, making the correct
choices about what to eat and also, getting enough physical exercise.
Where we live is probably one of the most important
factors that affect our nutrition. Food storage and transportation affects
the nutritive value of food. In Britain we cannot naturally (without the
aid of glasshouses) grow oranges, bananas, peaches, melons and certain
other fresh foodstuffs, so we import from countries miles away. To prevent
deterioration in transit, the holds of ships are sprayed with insecticides
to prevent foreign insects entering our country. Some crops are transported
in an unripe state; bananas for example, are held in 'ripening' sheds
until they are ripe enough to take to the fruit and vegetable markets
to be sold to the supermarkets and greengrocers.
We do not have more than one growing season in this
country for the majority of fruit, vegetable and grain crops. So again,
we need to import them. Some crops, for example fresh tomatoes and courgettes
from Spain, are grown and air-freighted into Britain on an almost daily
basis.
Food preservation methods also affect the nutritive
value of food. Years ago, people would pickle, dry, smoke, preserve in
salt, bottle fruit, make jam, or store root vegetables in dark places,
now all we have to do is drive to a supermarket to buy anything we want.
However, food is known to be more nutritious the less processed it is
and the fewer miles it has travelled.
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How can we ensure good nutrition?
Good nutrition may be achieved through various aims. Encouraging organic
food production is one way and where time, garden and energy allow, growing
our own fruit, vegetables and herbs. Organic food has lower levels of
contaminants, such as pesticides, antibiotics and nitrates and higher
levels of a variety of essential nutrients (Ref: Journal of Science,
Food and Agriculture 'A comparison of organically and conventionally grown
foods: results of a review of the relevant literature', K Woose, D Lange,
C Boess, KW Bogl. 74, 281-293, 1997).
Ideally, one should consume a wholesome diet of simply prepared, unprocessed,
unrefined foods with plenty of fresh vegetables, legumes, fish, fruit,
nuts, grains and a limited amount of meat, dairy and eggs. However, life
isn't quite like that, and the unhealthy foods such as cakes, biscuits,
chocolates, buns, confectionery, burgers, crisps, ready-made pies and
pastries, tea, coffee, fizzy drinks and alcohol can be very tempting.
Exercise should be included in 'good nutrition' because regular physical
exercise helps the content become stronger and to function more efficiently,
providing greater endurance. Exercise enhances the transport of oxygen
and nutrients into cells. At the same time, exercise encourages the transport
of waste products from the tissues of the content to the bloodstream and
ultimately to the eliminative organs. The end-result is increased stamina
and energy levels.
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Do we eat to live, or live to eat?
It may depend on where we live and the culture to which we belong. In
the more affluent areas of the country and of the world, people tend towards
living to eat and satiate the taste buds: the result is a growing statistic
of obese people. Whereas in poorer parts of the country or of the world,
people tend to eat to live and the equivalent of one meal a day is considered
fortunate: the result is growing starvation. Geographic location and politics
all have a part to play as well.
It is the responsibility of all of us to maintain the health of the planet,
to enable the world's farmers to grow enough food of sufficient quality
to nourish the physical bodies of the human race.
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Tips for a healthy lifestyle
- Make intelligent food choices.
- Chew food thoroughly before swallowing.
- Stop Smoking.
- Exercise regularly.
- Make intelligent drinks choices.
- Drink plenty of fresh water daily.
- Check your posture when sitting or standing for a length of time.
- Moderate the intake of 'known' unhealthy foods
- Create positive thinking habits - I can't go without chocolate / a
cigarette / a drink - becomes
- I will have a chocolate / cigarette in an hour or so / perhaps wait
until tomorrow.
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Landmarks in the knowledge of nutrition and
health (3)
| 1750s |
~ Scurvy (caused by Vitamin C deficiency) treated by
lime juice |
| 1830 |
~ Rickets (poor Calcium absorption caused by lack of
Vitamin D) treated by cod liver oil or butter |
| 1850 - 1900 |
~ Germ theory of disease. Improved hygiene, decline
of infectious disease and childhood mortality became an issue. Immunization
became popular against common diseases |
| 1900 |
~ Urbanization brought city slums. Malnutrition found
in some from poor working-class backgrounds |
| 1905 |
~ The search for vitamins and accessory food factors
expanded |
| 1906 |
~ School meals started in the UK |
| 1918 |
~ Concept of protective foods: milk, fruit, vegetables
|
| 1919 - 49 |
~ Search for accessory food factors and vitamins by
the Medical Research Council in the UK carried out |
| 1933 |
~ Milk Marketing Boards in the UK began encouraging
broader use for milk |
| 1940 - 45 |
~ The success of British food policies and rationing
|
| 1950s - 70s |
~ Intensive rearing of animals for human consumption
~ Cheap food
~ Blossoming of food industry, multinationals, convenience foods and
supermarkets
~ Food safety, food technology, food labelling and RDAs
~ Vitamin and biochemical research but dwindling research in other
aspects of human nutrition |
| 1980s - 90s |
~ Developing countries adopted 'Western' diets and Western
diseases
~ Western food mountains
~ Tariff adjustments, the Common Agricultural Policy and the World
Trade Organisation all affected the international trade in food |
| 1990s - present day |
~ Scientific developments, advances in knowledge and technology
~ Greater understanding of relationship between diet and health
~ Food safety scares, concern about animal husbandry practices,
call for more sustainable agriculture and greater accountability
in food standards
|
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References
- Collins Millennium Dictionary, 2000.
- Beck's Nutrition & Dietetics for Nurses. H. M. Barker. Churchill
Livingstone, 1991.
- Human Nutrition & Dietetics. Garrow, James & Ralph. Churchill Livingstone
2000.
- Nutrition Concepts and Controversies, Sizer & Whitney, 6th ed.
West. 1994.
- Technical Memorandum 597, Maff Project 4350, Campden Food and Drink
Research Association, 1990. 'Analytical survey of the nutritional composition
of organically grown fruit and vegetables'. R Pither and MN Hall.
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