UNIT 1: HEALTHY NUTRITION
1.1. INTRODUCTION TO INTEGRATED SCIENCE
1.1.1. Definition and rationale of integrated science
human survival depends on knowledge through the exploration of the
environment. Science provides knowledge while technology provides ways
of using this knowledge. It is therefore very important to be aware of the
global dimension of science needed in our lives in order to effectively deal
with every day situation. The word “integrated” means “to restore the whole,
to come together, to be a part of, to include.” Integrated science is a subject
which incorporates the knowledge base of all the science fields, both physical
and life sciences and these science fields are included in one subject as a
whole “integrated science” in that the fields of science are not segmented.
It is a subject which offers experiences which help people to develop an
operational understanding of the structure of science that should enrich their
lives and make them more responsible citizens in the society.
Hence, integrated approach of learning science is appropriate as science
knowledge is a tool to be used by every person to effectively deal with real
world problems and life.
For examples, when you are studying digestion process of animals, you will
need the knowledge of chemical processes. Another example, in describing
the physics of light, we show how this applies to the inner workings of our
eyes, which, in turn, are sensitive to visible light in great part because of the
chemical composition of our atmosphere.
1.1.2. Interconnection between science subjects
The purpose of science is to produce useful models of reality which are used
to advance the development of technology, leading to better quality of life for
man and the environment around him.
There are many branches of science and various ways of classifying them.
One of the most common ways is to classify the branches into social sciences,
natural sciences and formal sciences.
Social sciences deal with the study of human behavior and society. Examples
of these are psychology and sociology. Natural sciences deal with the study
of natural phenomena, for example lightning, motion, and earthquakes all
which can be observed and tested.
Examples of these are physics, chemistry and biology. Formal sciences deal
with mathematical concepts and logics. An example of this is mathematics.
Note:
–– Chemistry mainly deals with the study of salts, acids and their reactions.
For a physicist to understand the working mechanism of chemical cells,
help is sought from a chemist. On the other hand, the reasons behind
the various colours observed in most of the chemical reactions are
explained by a physicist.
–– Petroleum products are dealt with by the chemist, but the transportation
of such products make use of the principles of physics.
–– In Biology, the study of living cells and small insects by a biologist
requires magnification. The concept of magnification using simple or
compound microscope is a brain child of a physicist. A good physicistneeds to have good health.
1.1.3. Relationship between sciences with other subjects
The concepts of science and other subjects might be expanded or explainable
in broader senses than you might have been exposed to, this should then
predict not only the interconnection senses already known, but should also
predict much broader interconnections. This might be useful to you and our
future civilization.
Science is about observation and experimentation of things in the physical
and natural world. If there no creative ideas, no destructive ideas, just more
ideas of the same things that exist can this be healthy? There is such a thing
as inductive reasoning not just deductive reasoning.
Now, science is the practical application of scientific knowledge. So we
could have science as a conservative subject, or we could have science as
a creative (conservative and destructive) subject, then leading to smaller or
larger sets of science.
Note:
–– In Geography, weather forecast, a geographer uses a barometer, wind gauge, etc. which are instruments developed by a physicist.
–– In Agriculture, the water sprinkler, insecticide sprayer, etc. make use of
the principles developed by physicists.
–– In History, the determination of age fossils by historians and
archaeologists use the principle developed by physicists.
–– In games and sports, accurate measurement of time, distance, mass,and others uses instruments developed by physicists.
Food nutrients include macro and micro nutrients. Macro nutrients are
needed by the body in large quantities. They include proteins, carbohydrates
and lipids while the micro nutrients are needed in small amount and they
include mineral salts and vitamins.
The foods that we eat contain different types of nutrients. It is therefore
essential that we know the components of the food that we eat in order to
live healthy lives. There are three main food groups such as: energy giving
foods, body building foods and protective foods.
Energy giving foods are necessary to provide energy for cell metabolism.
They include: carbohydrates and lipids. Some energy giving foods include
potatoes, banana, rice, maize etc.
Body building foods are needed to promote growth and tissue repair.
These include proteins and can be found in the meat, eggs, fish, milk, beans,
cassava leaves, etc.
Protective foods allow a good functioning of the body, and protect the body
against some deficiency diseases. They include minerals and vitamins. The
minerals can be found in fish, beans, kitchen salt and mineral water; and
vitamins are found mainly in vegetables and fruits.
Food nutrients
Food contains mainly two classes of nutrients, organic and inorganic. The
inorganic nutrients include mineral salts like calcium, phosphorous and
others like water. The organic nutrients include proteins, carbohydrates,
lipids and vitamins.
The materials that an animal’s cells require but cannot synthesize are called
essential nutrients. There are four classes of essential nutrients: essential
amino acids, essential fatty acids, vitamins, and minerals.
1.2.1. Functions of food nutrients
a. Minerals
Mineral are also called micronutrients because we require them in very small
quantities. They constitute about 1% of an organism by weight. Even though
they are required in a very small amount, they are nonetheless essential for
human body processes.Table 1.1: Principal minerals
Classification of minerals
The classification of minerals is based upon their requirement rather than
on their relative importance. Mineral nutrients are needed in a precisesmall amount. The five major minerals needed in human body include
calcium (Ca2+), phosphorus (H2PO4-), potassium (K+), sodium (Na +) and
magnesium (Mg2+). Mineral nutrients are grouped into two groups of mineral
salts: the macronutrients or major elements and the micronutrients or
trace elements.
Macronutrient or major elements are minerals needed by humans in a relative
large amounts (greater than 200 mg/day). Their examples include nitrogen
(NO3-), phosphorus (H2PO4-), sulfur (SO42-), calcium (Ca2+), sodium (Na+),
chlorine (Cl-), magnesium (Mg2+), and iron (Fe2+ or Fe3+). Micronutrients or
trace elements are those which are needed in minute amounts (a few parts
per million). Examples include manganese (Mn2+), iodine (I-), zinc (Zn2+),
molybdenum (MoO4-).
Human body requires mineral nutrients to survive and to carry out daily
functions and processes. Minerals keep humans healthy and have key roles
in several body functions. Humans receive minerals by eating plants that
absorb minerals from the soil and by eating meat and other products from
animals, which graze on plants. The deficiency of mineral nutrients results
into body functional disorders and diseases. Most are found in the blood and
cytoplasm of cells, where they assist basic functions. For example, calciumand potassium regulate nerve and muscle activity
b. Vitamins
Like minerals, vitamins are also essential substances for the human body to
function properly. They are required for metabolism, protecting health and
for proper growth in children.
These are referred to as micro-nutrients. This is because our bodies require
them in very small quantities but they are very important. Depending on thevitamin, the required amount ranges from about 0.01 to 100 mg per day.
Vitamins classification
There are thirteen vitamins required by human body. They are classified by
their solubility, whether they dissolve in water or in fats.Table 1.3 Water-soluble and fat-soluble vitamins
• Water soluble
These are vitamins C and B. They are called water soluble vitamins because
they dissolve easily in water. They also dissolve when vegetables containing
these vitamins are cooked for long time.
NB: We must never overcook vegetables.
• Fat soluble.
These consist of vitamins A, D, E, and K. They are called fat vitamins
because they dissolve easily in oil and fat.
NB: We fry vegetables in some oil to be able to benefit from vitamin A, D, E,
and K in them. If we only oil boil or steam them, our bodies will not be able
to extract the vitamin in vegetables.
The vitamins are required for metabolism, protecting health and for proper
growth in children. Vitamins also assist the formation of hormones, blood
cells and genetic material.
Vitamins require no digestion and are absorbed directly from the smallintestine into the blood stream. Features shared by all vitamins:
–– They are not digested or broken down for energy
–– They are not synthesized into the body structures (are essential)
–– Most are rapidly destroyed by heat.
–– They are essential for good human health (needed in a very small amount)
–– They are required for chemical reactions in cells, working in association with enzymes.
Like minerals, vitamins are also essential substances for the human body to
function properly. They are required for metabolism, protecting health andfor proper growth in children.
c. Carbohydrates
They are macronutrients that provide our bodies with energy and warmth.
The word carbohydrate suggests that these organic compounds are
hydrates of carbon. Their general formula is Cx (H2O)y . The general function
of carbohydrates is to provide energy that is used in cellular metabolism.
Carbohydrates are divided into three groups including the monosaccharides
(single sugars: glucose, fructose and galactose), disaccharides (double
sugars: sucrose, maltose and lactose) and polysaccharides (many sugars:
starch, glycogen and cellulose).
NB: We need carbohydrates to do work also to keep our bodies warm.Table 1.5: Types of disaccharides and their monomers
The carbohydrates are energy giving nutrients. They are burned by Oxygen in
a process of cell respiration to produce energy to be used in cell metabolism.
The common know monosaccharides of carbohydrates is glucose with
molecular formula C6H12O6. If is burned by Oxygen, it produces energy as
shown in equation of cell respiration below: C6H12O6 +6 O26 CO2 +6 H2O+
Energy (ATP + heat).
All monosaccharides and disaccharides have the following characteristics:
sweet taste, soluble in water and lower molecular mass. In the same way
that two monosaccharides may combine in pairs to give a disaccharide,
many monosaccharides may also combine by condensation reactions to
form a polysaccharide. The polysaccharides like starch are not soluble inwater, and do not have the sweet taste.
d. Lipids (Fats and oils)
Fat sometimes ‘lipids’ refers to both fats and oils. Where by fats and oils
have the same basic chemical structure but their appearance differs at room
temperature that is, fats are solids at room temperature while oils are liquids
at room temperature. Fat is composed of three elements which are carbon,oxygen and hydrogen.
Sources and classification of lipids
Fats and oils are obtained from both the plants and animals. And fat is
present in food either as visible fat or invisible fat.
Visible fat is the one that is easily seen or detected in food for example; fatin meat, butter, margarine, lard, suet and cooking fat and oil.
Invisible fat is the part of food that is not easily seen for example fat with
in lean meat, egg yolk, flesh of oily fish, groundnuts, soya beans, avocado
and fat found in prepared foods, for example, pastry, cakes, biscuits, Frenchfries, pancakes, croquettes.
Lipids are of different types as it is summarized in the following table
Table 1.6: Lipids, structure, main role and features
e. Proteins
These are also referred to as macro-nutrients. The protein are also called
body- building food.
Proteins are made of complex molecules which contain elements like oxygen,
hydrogen, carbon, nitrogen and sometimes Sulphur and phosphorous. The
protein molecules are made up of small units calledAmino acids joined together like links in a chain.
There are 21 different amino acids and each has its own chemical name.
Different proteins are made when different numbers and types of amino acids
combine through a covalent peptide bond. Proteins are therefore known as
polypeptides.
Examples of proteins:
a) Collagen, myosin and elastin found in meat,
b) Caseinogen, lactalbumin, lacto globulin found in milk,
c) Avalbumin, mucin and liporitellin found in eggs,
d) Zein found in maizeThe 21 different amino acids found in protein are:
They are used to repair, to build, to maintain our bodies; to make muscles
and to make breast milk during lactation period. The proteins are classified
into two categories: animal or complete proteins and plant proteins orincomplete proteins.
Functions of proteins
Proteins are large organic compounds formed by amino acids and they are
not truly soluble in water. In addition to carbon, hydrogen and oxygen, proteinsalways contain nitrogen, usually Sulphur and sometimes phosphorus.
1.2.2. Balanced diet and food service techniques
a. Balance diet
Eating a balanced diet means eat at least 5 portions of a variety of fruit
and vegetables every day (see 5 A Day), base meals on higher fibre starchy
foods like potatoes, bread, rice or pasta, have some dairy or dairy alternatives
(such as soya drinks) eat some beans, pulses, fish, eggs, meat and other
protein
Food variety means eating a wide variety of foods from each of the five food
groups, in the amounts recommended. Eating many different foods helps
maintain a healthy and interesting diet which provides a range of different
nutrients to the body. Eating a variety of foods promotes good health and
can help reduce the risk of disease. ( https://www.google.balanced diet chart
for family)
The nutritional requirement is influenced by age, sex, growth, pregnancy
and breastfeeding, illness, psychological and emotional stress, activity
level and other factors like smoking and drinking. Biological factors include
age, gender, growth, disease states, and genetic makeup. Among the no
biological factors, socio-economic status is the most important. Poverty is
one of the major socio-economic causes of variation in nutrient intake, and it
also impacts nutrient requirements. ( https://www.google.balanced diet chart
for family)
Example:
Aging is linked to a variety of changes in the body, including muscle loss,
thinner skin and less stomach acid. ... Low stomach acid can affect the
absorption of nutrients, such as vitamin B12, calcium, iron and magnesium.
Although the recommended breakdown of carbohydrate, protein, and fat are
the same for both genders, because men generally need more calories, they
also require higher total intake of each of the macronutrients. Women need
fewer calories than men, but in many cases, they have higher vitamin and
mineral needs.
Reference Intakes
Nutritional needs vary depending on sex, size, age and activity levels so use
this chart as a general guide only. The chart shows the Reference Intakes
(RI) or daily amounts recommended for an average, moderately active
adult to achieve a healthy, balanced diet for maintaining rather than losing or
gaining weight. The RIs for fat, saturates, sugars and salt are all maximum
amounts, while those for carbs and protein are figures you should aim to
meet each day. There is no RI for fibre although health experts suggest wehave 30g a day.
A balanced diet is one that contains all nutrients required in health in
appropriate proportion. A balanced diet must should contain all food groups
such as: body building food, energy giving food and protective food in an
appropriate amount. A balanced diet help a person to:
–– Make you strong
–– Provide better health
–– Make you more productive–– Ensure strong immune system
It’s not hard to include foods from the five food groups into appetizers and
meals. Some suggestions include:
–– Vegetables and legumes – raw or cooked vegetables can be used as
a snack food or as a part of lunch and dinner. Salad vegetables can be
used as a sandwich filling. Vegetable soup can make a healthy lunch.
Stir-fries, vegetable patties and vegetable curries make nutritious
evening meals. Try raw vegetables like carrot and celery sticks for a
snack ‘on the run’.
–– Fruit – this is easy to carry as a snack and can be included in most
meals. For example, try a banana with your breakfast cereal, an apple
for morning tea and add some berries in your yoghurt for an afternoon
snack. Fresh whole fruit is recommended over fruit juice and dried fruit.
Fruit juice contains less fibre than fresh fruit and both fruit juice and
dried fruit, and are more concentrated sources of sugar and energy.
Dried fruit can also stick to teeth, which can increase the risk of dental
caries.
–– Bread, cereals, rice, pasta and noodles – add rice, pasta or noodles
to serves of protein and vegetables for an all-round meal. There are
many varieties of these to try. Where possible, try to use wholegrains
in breads and cereals.
–– Lean meat, fish, poultry, eggs, nuts, legumes and tofu – these can
all provide protein. It’s easy to include a mixture of protein into snacks
and meals. Try adding lean meat to your sandwich or have a handful
of nuts as a snack. You can also add legumes to soups or stews for an
evening meal.
–– Milk, yoghurt and cheese – try adding yogurt to breakfast cereal
with milk, or using cottage cheese as a sandwich filling. Shavings of
parmesan or cheddar can be used to top steamed vegetables or a
salad. Use mostly reduced fat products.
Feeding on unbalanced diet for a longtime may lead to malnutritional
diseases. Malnutrition means feeding on a meal lacking some food nutrients
(deficient diseases), or on a meal with all food nutrients but in unappropriated
amount (over eating).
Some deficient diseases include: kwashiorkor (caused by the meal lacking
proteins), marasmus (caused by the meal lacking overall nutrients), and
goitre (caused by the meal lacking iodine). The diseases caused by over
eating include: obesity, a condition in which excessive fats are deposited
in the body. More malnutritional diseases are described in the tables abovedescribing functions of minerals and vitamins.
b. Basic food service technics
They are many different approaches of serving food. An operation should use
a service style that is the best to satisfy its family members. The traditional
table service provides service for family members who are seated at table.
The English service comparable to Rwandan style is a type of service known
as “family style service”. In this service the big dish is placed in front of thehost along with serving plate and family members serve themselves.
• Principles for meal service
The family style meal service allows participants to eat together and to
make food choices based on individual appetites and food preferences. It
promotes mealtime as a learning experience to help participants develop
positive attitudes toward nutritious foods, share in group eating situations,
and develop good eating habits. Family style meal service can be conducted
in a variety of ways. For example, participants may help in preparing for the
meal by clearing the table and setting places, sharing conversation during
the meal, and cleaning up after the meal.
Family style meal service operates as follows:
–– All required meal components are placed on the table at the same time.
–– Participants may serve themselves from serving dishes that are on the table
–– Adults supervising the meal help those participants who are not able to serve themselves.
–– Participants can make choices selecting foods and in the size of the serving.
–– A supervising adult actively encourage family members to serve
themselves and offers the food item again later in the meal if member
(s) initially refuse the food or take a very small portion. Adult should
model good eating habits while supervising participants at the dining
table.
• Standards of serving food temperatures
The importance of temperature
The crucial important part of food safety in the home is to keep hot food hot
and to keep cold food cold. For safety it is vitally important to keep food out
of that danger zone.
The food being served should be kept at specified range and appropriate
temperature (T):
Note:
–– The temperature danger zone for bacteria reproduction and growth: 5OC < T < 63OC, food is not suitable for eating.
–– Bacteria do not multiply and start to die at 63OC above and do not grow and multiply at 5OC below.
End unit assessment
1. Analyze the importance of food nutrients.
2. Explain the importance of a balanced diet.
3. Explain how the condition factors (age, gender; activity; pregnant and breastfeeding mothers) affect the dietary needs of humans.
4. Justify the different functions of food nutrients in the body.
5. Classify vitamins and minerals as nutrients.
6. Organize the diet components in food groups.
7. Organize a list of foods that are good sources of specific food nutrients.
8. Prepare a balanced diet
9. Discuss services techniques of healthy diet.10. Recognize the role of integrated science in everyday life experiences
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