HUMAN ECOLOGY DEPARTMENT

FOOD, NUTRITION & HEALTH NOTES

GRADE 10

TOPIC: NUTRITION AND HEALTH

SUBTOPIC: 3) CLASSIFICATION OF NUTRIENTS

Nutrients are chemical substances obtained from the foods we eat. They are needed to build
and repair body tissues, give energy, carry out all body functions, prevent nutritional diseases
and give overall excellent health. There are six (6) nutrients and they are classified into two
groups which are:

a) Macronutrients- those needed in the body in large amounts example; carbohydrates,

protein, fats and water.
b) Micronutrients – those needed in the body in smaller amounts such as most vitamins
and minerals

Carbohydrates protein and fats are called energy-giving nutrients or caloric nutrients because
these are the ONLY nutrients that provide energy to the body. The unit used to measure
energy is called kilocalories.

1 gram of carbohydrate gives 4 kilocalories

1 gram of Protein gives 4 kilocalories

1gram of fat gives 9 kilocalories

1 gram of alcohol gives 7 kilocalories

CARBOHYDRATES

Carbohydrate is made up of the elements Carbon, Hydrogen and Oxygen. The smallest unit
of carbohydrate is GLUCOSE. It is made in the leaves of green plants during the process of
photosynthesis. Photosynthesis is the process by which green plants make starch (simple
carbohydrate) in the presence of chlorophyll, sunlight, water and carbon dioxide gas. This
provides food for the plant to grow and produce food for humans and animals.

The chemical formula for photosynthesis is:

CLASSIFICATION OF CARBOHYDRATES

1. MONOSACCHARIDE or Simple Sugars – These are the common base units from
which other carbohydrates are built. They are soluble in water and of varying
sweetness. There are 3 of them namely:
a) FRUCTOSE- found in fruits, plant juices and honey and called “Fruit sugar”
b) GLUCOSE –This is the form of carbohydrate that the body uses for energy and
the end product of carbohydrate digestion. It is then circulated through the blood
stream and then into the cells to provide energy. It is also called “blood sugar”
c) GALACTOSE – found in milk of mammals, where it forms part of milk sugar,
lactose.

2. DISACCHARIDES or Double Sugars- These are made up of TWO monosaccharide

units joined together. They are also soluble in water. They are broken down into
glucose during the digestion process. There are 3 types namely:
a) SUCROSE- this is formed from one unit of glucose and one unit of fructose. It
comes from sugar cane, beet and present in some fruits and vegetables. It is very
sweet and is called “table sugar”
b) LACTOSE- This is formed from one unit of glucose and one unit of galactose. It
is found in the milk of mammals to supply the baby. It is not as sweet as glucose.
 c) MALTOSE- It is made from two units of glucose and is found in cereals where it
is formed during germination eg barley. It is called “malt sugar”
3. POLYSACCHARIDES- These are also called Complex Carbohydrates and are made
up of varying amounts of monosaccharide units. They are insoluble in cold water and
are tasteless. They are namely:
a) STARCH – It is made from many units of glucose joined together. It is formed
during photosynthesis and is the main food reserve in plants. It is found in the
roots of vegetables, cereals and legumes.
b) DEXTRIN – This is formed when foods containing starch are baked or toasted eg
bread. It forms part of the crust and is more soluble than starch.
c) CELLULOSE- This is formed by plants from glucose units joined together to
form a strong structural network. They support the stem, leaves, bark, husks and
seeds. It is not digested in humans but forms dietary fibre needed to clean the
colon and prevent constipation and colon cancer. There are two types of dietary
fibre
i) Soluble – These attracts water and turns to gel during digestion, causing
digestion to be slower. It is found in oats, barley, nuts, seeds, beans, lentils,
peas and some fruits and vegetables. They help to lower the risk of heart
disease
ii) Insoluble- found in wheat bran, vegetables and whole grains. It adds bulk
to the stool and helps food pass more quickly. It cleans the colon and
prevent constipation and colon cancer.

d) PECTIN- Formed by some plants eg plums apples and other fruits. It forms gels in
water and is responsible for the setting of jams and jellies. It can be commercially
extracted.
e) GLYCOGEN- This is formed after digestion in humans and animals. It is a store
for excess carbohydrate in the body and is stored in the liver.
FUCTIONS OF CARBOHYDRATES

● Most important source of energy to the body

● Protein sparer- prevents protein from being used up as energy but instead be used to
build and repair body cells.
● Prevents ketosis by allowing fatty acids to be used up efficiently
● Provides a storage for energy in the form of glycogen
● Provides dietary fibre to clean the colon and prevent constipation and colon cancer
● Provides sweetness for foods

SOURCES OF CARBOHYDRATES

Sugars- sugar, syrups, jellies, jams, fudge , cakes, sweetened beverages and fruit juices

STARCHES- cassava, potatoes, legumes, yam, plantains, cereals etc.

HEALTH EFFECTS

Obesity, Dental caries, Diabetes

FAT/LIPID

Fat is another energy nutrient that is a concentrated source as it provides twice the amount of
energy as carbohydrate and protein. It is made up of the elements carbon, hydrogen and
oxygen

TRIGLYCERIDE

The basic unit of fat is called triglyceride and it is the fat found in the blood. It is made up of
glycerol and 3 fatty acids. It is the main constituent of body fat in human, animals and plants.
When you eat, your body converts any calories it does not use right away into triglycerides.
They are stored in fat cells. Later , hormones release it for energy between meals. High
triglyceride in the blood lead to increased risk of stroke, heart attack and heart disease.

Chemical structure of triglycerides

DIFFERENCE BETWEEN FATS AND OILS

● Fats usually come from animal source and are solid at room temperature eg. Lard
(pork fat), suet (beef Fat), butter, margarine.

● OILS – come from plant sources and are liquid at room temperature. They contain
more mono and poly unsaturated fats, with the exception of coconut oil which is a
plant based saturated fat’ eg. Olive, canola and corn oil.

WHAT IS CHOLESTEROL?

A waxy fat-like substance found in the cells of the body. The body uses it to make hormones,
vitamin D and other substances to help in the digestion of food. Your body makes all the
cholesterol it needs. It is also found in foods from animal sources such as egg yolks, meat and
cheese. Too much of it in the blood can cause plaque which blocks the arteries and lead to
atherosclerosis and coronary heart disease.

What is ‘Good Fat’- High-density lipoprotein (HDL) cholesterol is known as the "good"
cholesterol because it helps remove other forms of cholesterol from your bloodstream. Higher
levels of HDL cholesterol are associated with a lower risk of heart disease

What is ‘Bad Fat’- LDL is a lipoprotein that carries large amounts of cholesterol within its
core. LDL cholesterol is often called “the bad cholesterol”. Elevated LDL can significantly
increase the risk for developing premature cardiac disease and stroke in both men and women
(and in some cases in children too)

What are Fatty Acids?

Fatty Acids are the building blocks of the fat in our bodies and in the food we eat. During
digestion, the body breaks down fats into fatty acids, which can then be absorbed into the
blood. Fatty acid molecules are usually joined together in groups of 3, forming a triglyceride.

Classification of fatty acids

There are 3 types of fatty acids namely:

● Saturated – These have only single bonds and formed from fatty acids and glycerol.
The carbon atoms are completely saturated with hydrogen atoms and can hold no
more. They come mainly from animal sources such as red meat ( pork, lamb, beef),
chicken skin, Whole –fat dairy products(milk, cream, cheese), butter, ice-cream, lard,
coconut oil, palm oil. They are solid at room temperature. (Saturation means full to
capacity)
 Chemical structure of saturated fat

● Unsaturated (monounsaturated and polyunsaturated)- These are called oils, because

they are liquid at room temperature. They may be mono or poly unsaturated. They are
mainly from plant sources and contain one or more double bonds. This means that it is
not saturated and so has the capacity to take more hydrogen atoms. In the case of one
double bond it is called monounsaturated fatty acid and more than one double bonds
is called polyunsaturated fatty acids, The latter is healthier, as it has less hydrogen
atoms which hardens the fat.

 Trans-fatty acid
an unsaturated fatty acid of a type occurring in margarines and manufactured cooking oils as
a result of the hydrogenation process, having a trans arrangement of the carbon atoms
adjacent to its double bonds. Consumption of such acids is thought to increase the risk of
atherosclerosis.
Hydrogenation solidifies liquid oils and increases the shelf life and the flavour stability of oils
and foods that contain them. Trans fatty acids are found in vegetable shortening and in some
margarine, crackers, cookies, and snack foods.

WHAT ARE ESSENTIAL AND NON-ESSENTIAL FATTY ACIDS?

What are the functions of fatty acids?

They're essential for the proper functioning of your brain, nerves and cells throughout body.
They also help regulate the inflammatory response. Essential fatty acids must come from
your diet as the body cannot make these, e.g. Linoleic acid. The non-essential fatty acids are
synthesized by the body and so the food eaten do not supply those. Two of the essential fatty
acids must come from your diet; your body uses them to make three more.

FUNCTIONS OF FAT IN THE DIET

● It is a concentrated source of energy. 1 gram gives 9 kilocalories. Healthy Fats are
Expended as Free Energy: The body needs the calories and macronutrients
contained in foods. You need to eat a set amount of healthy fats so that your body has
a balance that assists it in expelling calories and essentials as energy
● Create Healthy Fat Stores: There are certain reasons a person does have at least a
small amount of fat on their body. Whether it is to help with body heat in cold
climates or to have fat stores in case of sudden weight loss or lack of food, the body
needs some healthy fats so it can store it for these purposes.
● Helps the Body to Better Absorb essential Nutrients, Mineral, and Vitamins: Fats
that are healthy are beneficial to the body because they also help a person to absorb
essential nutrients, minerals and vitamins that they need for all of the organs and
systems to function optimally.
● Helps The Body to Maintain a Normal Body Temperature: You may already
understand that heavier people that possess more fat content on their body are warmer
 than those who possess nearly no body fat. The reason for this is that fat functions to
help the body to balance its core temperature.
● Boosts Your Immune System: There is a large role that eating healthy fats play in
protecting your body and systems from diseases, illnesses, and more. Getting the
recommended daily dosage of fat can really help you from falling prey and being
more prone to catch & contract diseases because of a weakened immune system.
● Contribute to the growth and health of nails, skin, & hair, and also help boost
hormone production.
● Improve the taste and texture of baked products and fried foods
● Acts as a protein sparer.

SOURCES OF FAT

There are two kinds of dietary fats: visible and invisible fat. Visible fats can be identified
easily and include oils, butter, animal fat, lard, suet, margarine, etc. Invisible fat, not visible
to naked eyes, is present in food items like wheat, rice and pulses etc., in small amounts,
pastries, snacks, avocado, cheese, Ackee, cakes, ice cream, milk etc.

ASSIGNMENT:

Find out:
1. What is stroke, arteriosclerosis, obesity, diabetes, and dental caries?
2. The effects of heat on carbohydrate and fats
3. How to test for sugars, starch and fat in foods

PROTEIN
Protein is made from the elements; carbon, hydrogen, oxygen and nitrogen. It may sometimes
also contain sulphur and phosphorus as well. In addition to carbon, hydrogen and oxygen,
protein contains nitrogen which makes it carry out special functions that the other energy
giving nutrients cannot do. That is why fat and carbohydrate are called ‘protein sparer’s in
order to save for the other important functions it must carry out. The nitrogen in protein is
needed for the following functions:
1. To make amino acids ( the building blocks of protein)
2. To make hair, nails, skin.
3. To make enzymes and hormones needed in all body processes
4. Needed for normal growth
5. Build and repair body cells
6. To make heme in haemoglobin which is the oxygen carrying pigment in red blood
cells
NB: The body cannot use nitrogen from the air and soil directly, and so has to depend on
microbes and green plants to convert it in a form that can be used.

WHAT ARE AMINO ACIDS?

These are the smallest unit/building blocks of protein. Many of them come together to form
chains of protein. There are two types:
● Essential amino acids
These cannot be synthesized by the body and must be taken in from the foods we eat. They
are required for growth.
The essential amino acids for all people are histidine, isoleucine, leucine, lysine, methionine,
phenylalanine, threonine, tryptophan and valine
● Non-essential amino acids
These are synthesized by the body or the body makes them for itself.

What exactly is the biological value?

The actual biological value isn't necessarily a thing in and of itself, its actually broken down,
like essential and non-essential, into two categories that help determine how many essential
amino acids a body contains in proportion to what is required of the body. Those two
categories?

● High Biological Value

● Low Biological Value

When a protein contains the essential amino acids in proportion to what their body requires,
they are said to have a high BV. If one or more of those amino acids are missing, or they're
present but in low numbers, then that protein is said to have a low BV.
What exactly makes Biological value so important?

While other aspects of healthy nutrition (carbs, fats) can be stored in the body for future use,
when amino acids aren't used, they leave the body. If you continue to eat a lot of food that has
low BV, then the full potential of a protein will not be fulfilled.

Are there any foods I can eat to ensure I am getting a lot of Biological value?

There are many foods that can help ensure you have a high BV, as opposed to low. Along
with foods that are known to have low value. They are listed below:

● High BV
● Meat - Poultry - Fish- Eggs- Milk - Cheese- Yogurt
● Low BV
● Plants - Legumes - Grains - Nuts - Seeds - Vegetables

WHAT ARE COMPLEMENTARY PROTEINS

● Complement Proteins. Complement proteins are two or more incomplete/low biological

value protein sources that together form a complete protein.
Complementary Protein Examples. Beans and rice are an example of complementary
proteins. Beans are low in specific essential amino acids that rice provides.

Here are some examples of food pairings that provide complementary proteins:
● soups or stews that include legumes and grains
● salads made with beans and nuts or seeds
● a peanut butter sandwich on whole-grain bread
● hummus with whole-wheat pita bread
● tofu or tempeh with brown rice or quinoa
● tofu stir-fry with whole-grain noodles and peanuts
● beans and brown rice

FUNCTIONS OF PROTEIN IN THE BODY

● For body building and growth
● For replacement, repair and maintenance of the body
● To make enzymes, antibodies and hormones
● Transport haemoglobin, lipoproteins and other substances in the body
● Secondary source of energy
● Needed to make, hair, skin , nails
● Helps to form red blood cells

FOOD SOURCES OF PROTEIN

ANIMAL SOURCES- Most animal sources are high biological except for gelatin, which is
the only animal protein of low biological value. Example meat, fish, poultry, dairy products,
eggs, soybeans.

PLANT SOURCES- Most plant sources are low biological except for soybean, which is the
only plant protein of high biological value. Examples are beans, nuts, and seeds such as chia
and flax.