Introduction
There is an old saying which states, "You are what you eat." But what exactly do we eat? What is our food made of and why do we need food anyway? These are the questions answered in this website. However, before we get started, we need to get to some idea of what is in the food we eat.
The need for food
All living organisms require energy to maintain themselves and also for growth, movements, etc. Green plants can make use of the energy of the sunlight by photosynthesis but other organisms need food to supply their energy needs. Thus the food that the organisms feed on contain a store of energy. This stored energy is called the potential energy.,
Energy cannot be created nor be destroyed, but it can be converted from one form to another. The potential energy stored in certain food substances may be set free in the form of kinetic energy during tissue respiration. These energy then enables the organism to do work. Thus the food must provide more energy than the organism uses to make up for this loss. Energy loss occurs even when the organism is inactive and thus even resting organisms require food.
Food too are needed to maintain health and prevent deficiency diseases such as cancer and many other kinds of health problems too like obesity which leads to heart cancer. And i do believe that part of that diseases in this world is cause by the ways people eat.
Nutrients are chemical substances in food which nourish the body, i.e. provide energy and materials needed by the body. The nutrients in the food we eat may be classified as follows.
2. Fats
3.Proteins
4.Vitamins
However, we had to note that Water and fibre are not under the classes of nutrients but under the classes of food This is because, under the classes of nutrients, they are all organic food substances as they are obtained from living organisms . They are compound of carbon. Though water and fibre are not under the classes of nutrients, they too are important to human beings.
Carbohydrates are
organic compound made up of the elements carbon, hydrogen and oxygen. The
hydrogen and the oxygen atoms are present in the ratio 2:1.Carbohydrates include
sugars, starch, the cellulose of plant cell walls and a number of related
substance. There are other substances which are slightly modified carbohydrates,
such as the chitin of the arthropod skeleton.
Carbohydrates are not only needed as a source of energy but also for the formation of nucleic acid in the DNA. It is also needed to synthesize lubricants, e.g. mucus which consists of a carbohydrate and a protein. The mucus lining the respiratory system in Man traps dust particles.
Carbohydrates is classified into three groups namely Monosaccharide, Disaccharides and Polysaccharides.
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Monosaccharide |
This is just simple sugars and can easily be found in sweet fruits and honey. Moreover, these kind of carbohydrates is very useful for ageing or sick people who have weak body and might not be able to break down the complex sugars into simple sugars to meet the body needs. These kind of carbohydrates can easily be absorbed by the cells of the body. |
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Disaccharides |
This is a more complex sugars. Therefore it might need the body enzymes to break it down into Monosaccharide. This can easily obtained from milk and even from sugar-cane. |
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Polysaccharides |
This include starch, glycogen and even cellulose. This is the most complex among the other two groups. Starch is one of the most important sources of carbohydrates in our food. It occurs plentifully in vegetable foods such as cereals, potatoes, tapioca, etc. |
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The total storage capacity of the body for carbohydrates is limited. An average person stores about 300 to 400 grams of carbohydrates in the muscles, which cannot be utilized by the brain for energy. Only 60 to 90 grams are stored in the liver for glucose conversion, equivalent to about two cups of cooked pasta or three typical candy bars. This is all the body has in reserve to keep the brain working properly. Once the glycogen levels are filled in both the liver and the muscles, excess carbohydrates are converted into fat and stored in the adipose tissue. Hence, excess carbohydrates become fat. In modern day society, it is sugar that makes a person fat much more that the amount of fat a person consumes. |
There are two types of fat. Saturated
and unsaturated fat. The types of fat occurring in animals body are
called saturated fats and a fatty substances usually found together with the
saturated fats is cholesterol. Cholesterol may get deposited on the
inside of the arteries and this may lead to heart attack and even
stroke. Unsaturated fat means vegetable fats and is much more healthier
than saturated fats. This is because fats found in vegetable is actually lower
than meat. For example:14 French fries can have 225 calories
and 11 grams of fats.
Foods rich in fats include butter, cheese, fatty meats, olives, many nuts, and seeds of castor oil, palm oil and many leguminous plants. Human can manufacture their own fat requirements, thus fat is not essential in the diet as they are usually contained in carbohydrates (staple food of human). Thus, fats should be avoided in the diet of people who have developed gallstones in their gallbladders and those who had heart attack.
Thus some authorities had recommended the dietary cholesterol be limited to 300mg or less per day.
Why is proteins important?
Protein is needed by children and
even pregnant woman in order to synthesis new protoplasm, i.e. for growth and
repair of worn out body parts. It is also needed for synthesis of enzymes,
hormones, antibodies, haemoglobin, etc. Hormones are chemical substances
secreted by certain parts of the body. They regulate bodily functions, so that
proper growth and development can take place. As enzymes and many hormones are
made of proteins, Therefore we can see how important proteins are to the body.
What will happen if their is not enough protein?
In human beings the average adult
needs 50to 100 gram of proteins a day. The deficiency of proteins
in the diet of children may lead to protein deficiency disease called
kwashiorkor.
Why do we have to be careful in consuming vitamins?
Vitamins have a reputation of
being essential for the health and they are often promoted as additional
supplements to the diet by drug companies. Indeed, drug companies make a fortune
each year by selling vitamin pills. Such pills may be needed by certain
groups such as young children, senior citizens or pregnant women but most of us
do not need vitamins supplements: we get all the vitamins we need from our diet,
provided we eat a good range of foods. In fact, it is possible to poison the
body by consuming too much vitamins. This happened to one Polar expedition
when a group of Italian explorers, who had ran out of food ate the liver of a
polar bear they had shot. Polar bear liver contains an enormous amount of
Vitamin D and these Polar explorers suffered the effects of vitamin D
poisoning, which resulted in several of them dying.
However, lack of vitamins in our diet may lead to deficiency diseases too. For example: In children, Lack of vitamin D may results in rickets-a disease characterized by poor teeth and bone formation. In adults, the deficiency may leads to osteomalacia- a softening of the bones.
Thus, this had shown that vitamins are unlike carbohydrates, proteins and fats. They are not energy-building nor body-building food. Thus they are required in small quantities, by animals, including man, for normal health and development. Different vitamins are found in different foods, but if we eat a varied diet which contains fresh, raw vegetables, we are likely to get most of the vitamins we need.
Minerals elements are
inorganic substances which do not provide energy but are dispensable to bodily
functions. We obtain minerals from other animals or from plants. In man, some
minerals are needed in large quantities but others are only needed in small
quantities. Those minerals required in large amounts are calcium, phosphorus,
sodium, chlorine, potassium and iron.
Some examples:
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Minerals |
Sources |
Requirements |
Deficiency may cause |
|
Calcium |
Milk,cheese,cereals, green vegetables |
|
|
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Iron |
Liver, egg yolk, bread, vegetables |
|
|
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Iodine |
sea fishes, seaweeds, fruits. |
|
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A Balanced Diet And Food values
A healthy Diet pyramid
One way of managing a balanced diet is through the "Pyramid Way" shown above. From the picture shown, it had clearly show that our staple food like bread/Rice should be eaten more by people. At the second level, the food mainly come from plants-vegetables and fruits. These level help to provide minerals, vitamins and fibres. The third level helps to provide protein, iron, calcium and zinc. The last level only provide calories and little else nutritionally. Thus most people should used them sparingly.
The pyramid shows a range of servings for each major food group. The number of servings actually depends upon the calories we need which in turn is related to basal metabolism of a person. According to the National Academy of sciences and on calorie intakes reported by the people in national food consumption surveys are :
| sedentary women and some older adults | 1600 calories |
| children, teenage girls, active women and many sedentary men. | 2200 calories |
| teenage boys, many active men and some active women. | 2800 calories |
So what does servings mean?
1 Servings mean: for bread, it's a slice. Servings can be different amount for different food., This had to follow the table given below.
In reality, servings only act as a guide so that we can easily measure how much we had over eaten some types of food.
Metabolism is the term used to describe all of the chemical reaction which occur inside the body. The basal metabolism rate is a measure of how fast chemical reactions are occurring when a person is completely at rest.
Our daily energy needs depend on
our basal metabolism and the physical activities we perform. Basal metabolic
rate also depends upon the climate, body size, age, sex and health of individual
For example, in colder countries, aperson metabolic rate is higher as compared
to a person living in tropics. WHY? This is because a person living
in a cold country tends to lose more heat to his surroundings. (as
shown)
Therefore we had to ensure that there is energy balance in our diet, i.e. energy intake should equal to the energy expenditure.
For further information:
This webpage gives further information of what i did:
http://www.nal.usda.gov/fnic/foodcomp/Data/SR17/wtrank/wt_rank.html
http://www.geocities.com/ying1113/
Chak
Hon Nee
Christina
Adeline Sung
Foo Chui Chen
well, we are the four phoenixes which are trying to keep u guys healthy by giving u guys some information on nutrition. Moreover, we really enjoy doing our project with each other. Not only that we had learnt new things we never know, we also learnt how to make our first web sites. And we had gain friendship and better understanding about each other too. Last but not the least we would like to thank Dr. Brown for giving us such an opportunity!! Therefore "Thank You" sir and hope that u enjoy our websites. So do others.
For any comments about website, please contact us:
Foo, Chak, Christina and Adeline.
