Food And Nutrition

A person is what he eats- this is often used as a metaphor.

Food is a composite mixture of substances which when consumed performs certain functions in the body. These functions are (1) yielding energy, (2) building and maintaining the body and (3) protecting the body and regulating the tissue functions.

Nutrition is the process whereby living organisms utilize food for maintenance of life, growth, the normal functioning of tissues and organs, and the production of energy.

Diet and Nutrients

Diet is the total solid or liquid foods consumed by an individual or by a population group, either on an average basis or during a specified period.

Nutrients are the constituents in food that must be supplied to the body in suitable amounts. These include water, proteins, fats and fatty acids, carbohydrates, minerals and vitamins.

Malnutrition

Malnutrition is an impairment of health resulting from a deficiency, excess or imbalance of nutrients.

Primary malnutrition may be due to several reasons which include (1) lack of food or means to have access to food, (2) lack of elementary knowledge of food and nutrition, (3) refusal to take foods, (4) fad foods and (5) lack of teeth or inability to chew.

Secondary malnutrition is due to some difficulty or alteration in the digestion, absorption or assimilation. A number of conditions responsible for this are (1) disorders of the gastrointestinal tract, (2) protracted immobilization, (3) fever, (4) surgery and (5) drug therapy.

Protein energy malnutrition (PEM) is the most common form of malnutrition affecting the millions of children in the under developed countries. This condition is rather uncommon in adults. The important contributory factors to PEM are (1) lack of resources to buy food leading to an inadequate food supply, (2) a bulky diet consisting very low calories, (3) diminished appetite because of infection and (4) ignorance of family members about nutritive values.

The Nutrients

Carbohydrates

There are three types carbohydrates- sugars, starch and fibre. Sugars are monosaccharides like sucrose. Starch is polysaccharide and is stored in plant roots, tubers or underground stems. Fibre  containing non-nutrient cellulose helps in the formation of bulk of the waste of digestive system.

Functions:

Ø  Provides main source of energy

Ø  Helps the body to use protein and fat efficiently

Ø  Supply fibre for better digestion 

Ø  Foods rich in carbohydrates supply other nutrients too.

Sources: Carbohydrates mainly come from the food groups of cerals, tubers, fruits, sweets etc.

Proteins

Proteins are made of amino acids. About 20 such amino acids are required by the human body of which the body cannot produce eight. These have to be supplied from outside and are known as essential amino acids. Protein from different plant sources may be combined in such a way that the result is equivalent in nutrient value to animal protein (goal of vegetarian diet).

Functions:

Ø  Helps to build new cells and maintain or repair the injured ones.

Ø  Used for energy when carbohydrates or fats are in short supply.

Ø  Protein foods are also rich in fats, carbohydrates, vitamins and minerals.

Ø  Takes part in defense mechanism.

Ø  Produces enzymes and coenzymes.

Sources: All animal foods (meat, poultry, milk, fish, etc.), nuts, dried peas and beans, lentils and plants foods (wheat, corn, rice, etc.).

Fats

Fats or lipids are made of fatty acids, triacylglycerol, phospholipids, glycolipids, etc. The  most important class of dietary fats from an energy perspective is triacylglycerol, constituting more than 90% of total dietary lipids.

Functions:

Ø  Supply essential fatty acids

Ø  Supply energy

Ø  Carry fat soluble vitamins

Ø  Give flavor to food.

Sources: meat, milk and milk products like cheese, cream, ghee, butter, ice cream, yoghurt, plant oils, nuts, eggs, etc.

Minerals and vitamins

                       Table-1: Fat soluble vitamins

Vitamin	Functions	Food Sources
Vitamin A	Prevention of nutritional blindness, phrynoderma, loss of skin integrity.	Liver, egg yolk, butter, milk, fatty fish, deep-yellow and deep-green fruits.
Vitamin D	Prevention of rickets and osteomalacia; helps formation of strong teeth.	Fish liver oils, fatty fish, egg, butter, cheese, full fat milk. Skin can produce vitamin D by the activity of altraviolet radiations of the sun falling on it.
Vitamin E	Acts as antioxidant; keeps oxygen in body from destroying other nutrients. Reproductive role in human being is still inconclusive.	Plant oils, whole grain cereals, eggs, meat, milk, green leafy vegetables.
Vitamin K	Helps blood clotting.	Green leafy vegetables, cereals, legumes, milk, eggs meat and fish.

                  Table-2: Water soluble vitamins

Vitamin	Functions	Food Sources
Vitamin C	Severe deficiency leads to scurvy. Helps in formation of collagen, metabolism of tyrosine, absorption of iron, bone formation and electron transport.	Citrus fruits, tomatoes, guava, pine apple, ripe papaya and some green leafy vegetables like drumstick amaranth.
Thiamin (Vitamin B1)	Severe deficiency leads to beriberi; deficiency also to impaired cellular functions.	Whole cereals, pulses (legumes), oilseeds and nuts, dried beans.
Riboflavin (Vitamin B2)	Deficiency leads to oral and facial lesions (damage to skin, dermatitis)	Liver, whole and skim milk powder, eggs, meat and fish, whole cereals, legumes and green leafy vegetables.
Niacin	Severe deficiency leads to pellagra (cracking of the skin)	Meat, poultry, fish, milk, liver, peanut.
Pyridoxin	Helps many biochemical functions, influences hormones, metabolism of lipid	Meat, liver, kidney, whole grain cereals, peanuts, soyabeans.
Cobalamin (Vitamin B12)	Deficiency leads to pernicious (deadly) anaemia.	All animal foods.

                          Table-3: Minerals

Minerals	Functions	Food Sources
Calcium	Deficiency leads to decrease rate of growth, negative calcium balance, osteoporosis, tetany.	Milk and milk products, sesame seed, green leafy vegetables, small dried fish.
Iron	Binds with protein to make haemoglobin	Liver, meat, egg yolks, dark green leafy vegetables, dried fruits, whole grain and iron fortified foods.
Iodine	Prevents goitre.	Salt water fish, sea food, iodized table salt.
Zinc	Helps healing, normal reproduction, cell growth.	Animal proteins.
Fluorine	Prevents dental caries.	Normally present in drinking water.

Balanced Diet

A balanced diet is one which contains all the proximate principles (protein, fat and carbohydrate), minerals and vitamins in due proportions and at the same time meeting the total energy requirements for maintaining health, vitality and well-being of a person (see Table). Experts agree that 12% of your daily intake of kilocalories should be from proteins, 30% or less from fats, and 50% from carbohydrates. Lack of balanced diet may lead to malnutrition.

              Table-4: Balanced diet in adult men and women

Food items (in gm)	Adult Men			Adult Women
	Sedentary	Moderate work	Heavy work	Sedentary	Moderate work	Heavy work
Cereals	460	520	670	410	440	575
Pulses	20	25	30	20	22.5	25
Egg or meat/fish	One egg or 30gm meat/fish			One egg or 30gm meat/fish
Leafy vegetables	40	40	40	100	100	50
Other vegetables	60	70	80	40	40	100
Roots & tubers	50	60	80	50	50	60
Milk	150	200	250	100	150	200
Oil & fat	45	50	70	25	30	45
Sugar/jaggery	30	35	55	20	20	40

            Source: Indian Council of Medical Research.

Measurement

Until the end of the eighteenth century, the study of material things was treated as a single aspect of human thought and called natural philosophy. But as knowledge increased it was found necessary to divide the study of nature into two main branches,

A. Physical sciences

B. Biological sciences

Physical science is the study of matter and energy. In physical science we study the properties of material i.e., metal, water, air etc. property is a feature of matter or the way it acts. Extreme hardness is the property of diamond. Black color is a property of coal and so on. Lemon juice taste sour. Perfumes evaporate easily.  These are few examples of properties of different substances.

We also study force and motion; electricity, sound, thermal energy and light. We study energy transfer.

The two main physical sciences are

A. Physics

B. Chemistry

It is difficult to make a clear-cut distinction between the two, but, broadly speaking, chemistry deals with the action of one kind of substance on another while physics is connected mainly with matter in relation to energy

Biological sciences deal with living things, while the physical sciences are connected with the properties and behavior of non-living matter.

Physics

The study of physics looks into much of the natural world around us. It ranges from the astronomically large, such as solar system, to the microscopically small, such as the atom. Although the study of physics is commonly divided into major topics like General Physics, Thermal Physics, Waves, Electricity and Magnetism, and Atomic Physics all these topics are related to two main ideas: Matter and Energy. Fig – 1 shows a simple concept map of physics.

MEASUREMENT OF PHYSICAL QUANTITY

Physical science is nothing but the basic knowledge of accurate measurement. Length, width, weight etc. are commonly measured quantities. These are all physical quantities. In physics physical quantity means a quantity that can be measured or the result of a measurement. Historically, people have always realized the need of standard weights and measures. From time to time these standards have been revised, improved and established by law.

Measurement

In general sense “To measure something using a standard unit and expressing it in terms of standard units is called measurement." In physical science, by measurement we understand comparison of size, weight or other phenomenon of similar objects. For example, it we ask the salesman what is the size or length of a saree? Then the sales might measure the saree using his hands and say "the length of the saree is 11 cubit (hands)". From this measurement, we understand that the length of the saree is 11 times the size of his forearm.

 

 

Units of Measurement

To measure any physical quantity a convenient fraction or standard of that quantity taken to which the quantity is compared with. This standard fraction is known as unit. In the preceding example, "hand" is used as a convenient fraction or standard in measuring the saree, which in physical science is called "unit". In this example, the unit of length is "hand". We shall learn details of the measurement units in the following topics although in the previous example we have used "hand" as a unit of measurement for length, it cannot be accepted universally. Why? As the lengths of hands vary from person to person, the measurement would not be a standard one and would be faulty. We must adopt some quantity which is accepted unanimously all over the world.

Fundamental and Derived Quantities

Although there are many physical quantities in physics, only a few are required to express them. Generally, length, mass and time – these three quantities are called fundamental quantities. These quantities are not dependent on each other or any other quantities. For example, the distance from home to school is 1000 meters and it takes 180 seconds to get there. Now the average speed from home to school can be obtained by dividing the distance by the time.

We can see that using distance (length) and time we are able to calculate another quantity "speed”. In other words, the quantity ‘speed’ is dependent on two other quantities, length and time, but length and time are independent of each other. In fact, apart from length, mass and time the other quantities are made up of the combination of these three quantities. Since these quantities are derived from three fundamental quantities they are called "derived quantities".

According to the dependence on measurements the physical quantities are divided into two types.

      (a) Fundamental quantity and

       (b) Derived quantity

(a) Fundamental Quantity:

"Fundamental quantities are those which do not depend on other quantities, rather other quantities Depend on them". For the purpose of measurements, scientists have identified four more quantities other than mass, length and time as fundamental quantities. These are thermodynamic temperature, luminous intensity, current and amount of matter.

(b) Derived Quantity:

"Derived quantities are those which depend on fundamental quantities and are derived from them." There are only seven fundamental quantities, but there can he numerous derived quantities; area, volume, force, velocity, density are few of the derived quantities.

Base and Derived Units

We know that units are required to measure a quantity. Since quantities are divided into two group namely fundamental and derived quantities, units are also divided into two groups based on the same principle. They are   

           (a) Base units and

           (b) Derived units.

Bellow are given two examples which explain and differentiate the two types of units. We know that, Area = length ´ Width.

According to the figure. Area of ABCD = AB ´ BC

Now, if AB = 3 meter and BC = 2 meter

Area of ABCD = 3 meter ´ 2 meter

                                = 6 square meter or m².

Here, "Square meter" is the unit of area. If we know the unit of length, which is base unit (meter), we can find out the unit of area (square meter) .

\Unit of Area = (unit of length) ²

Or, Square meter = (meter)²

\ Square meter or m² is a derived unit.

To find the unit of speed we need to divide the unit of

distance by the unit of time, That is,

Speed =

Hence, unit of  speed =

                                              =

                                              =

                                              = ms^-1

So we can see that the units of distance and time meter and second respectively are two fundamental units, from which we can determine another quantity (speed), yet meter and second do not necessarily depend on units of other quantities.

In the light of above two examples we may define base unit and derived unit as follows.

Base Unit:

The units of fundamental quantities are termed as base units. In other words,

"The units of quantities which are not dependent on each other or on units of any other quantities, rather, can he used to make up units of other quantities, are called base units."

Scientists have identified seven fundamental quantities. These are length, mass, time, thermodynamic temperature, current, luminous intensity and the amount of matter. So, these quantities also have seven different units and these are all base units. The units are meter, kilogram, second, Kelvin, ampere, candela and mole.

Derived Units:

The units of derived quantities are termed as derived units. In other words,

"The units which are based on the other base units are called derived units.'

There is no specific number of derived units since these can be made up of different combination of seven base units. For example, square meter, Newton, watt, etc.

Different Systems of Units

Different units are required to measure the quantities like length, mass and time. There are three different systems of units for measuring the fundamental quantities which are being used throughout the world. The systems are,

1.      C. G. S system : Under  this system the unit of length is centimetre (cm), the unit of mass is gram(g) and unit of time is second(s). For this reason system is also called Centimetre-gram-Second system or in short C. G. S system.

2.      F .P. S system : Under this system the unit of length is foot(f), the unit of mass is pound(lb) and the unit of time is second(s). For this reason this system is also called Foot-Pound-Second system or in short F. P. S system.

3.      M. K. S system : Under this system unit of length is meter (m), unit of mass is kilogram (kg) and unit of time is second. For this reason this system is also called Meter-Kilogram-Second system.  

The International System of Units

This system is abbreviated as S.I. from the French words ‘Le Systeme Internationale d’Unites’. The S.I. is maintained by the an agency called ‘The International Bureau of Weights and Measures’(BIPM) situated in Paris and it is updated every few years by an international  conference, ‘General Conference on Weights and Measures’ (CGPM) attended by representatives of all the industrial countries and international scientific and engineering organizations. Under this system the selected seven fundamental quantities and their respective base units are given in the following table.

Table 1: Fundamental quantities and their S. I. units.

Physical quantity	S. I. units	Symbol of unit
Length	Metre	m
Mass	Kilogram	kg
Time	Second	s
Temperature	Kelvin	K
Current	Ampere	A
Luminous Intensity	Candela	cd
Quantity of matters	mole	mole

Scientific Notation : Use of Power of 10

Scientists often use such numerical values which can be very large or very small. For example, the speed of light is approximately 30,00,00,000 ms^-1. The electrical charge in an electron is 0.00000000000000000016 coulomb.

Normally it is very difficult to count all the Zeroes in the previous two examples. These values are difficult to grasp, remember, read and write. We may conveniently use the power of 10 to eliminate this problem. For example, we may simply express the velocity of light as 3 ´ 10⁸ms^-1.

We know 10⁰ = 1

                      10¹ = 10

                      10² = 100 (= 10 ´ 10)

                      10³ = 1000 (=10 ´ 10 ´ 10) etc

The power is expressed as to how many zeroes are there after 1 and the raised power is termed as index. In the preceding example 0, 1, 2, 3 etc. are indices (plural of index). We may observe the similar procedure in case of numbers less than one.

                      10^-1 =  = 0.1

                      10^-2 =  = 0.01

                      10^-3 =  = 0.001

Here are some examples of converting some very big and very small numbers into scientific terms,

                      6733000000 = 6.733 ´ 10⁹

                      0.00000846 = 8.46 ´ 10^-6

The law of indices can be applied in expressing scientific notation. The laws are as follows:

                      10^m ´ 10ⁿ  = 10 ^{m + n}

Here m, n can be either positive or negative e.g. e 10⁶ ´ 10⁷ = 10⁶⁺⁷ = 10^1`3

                      10⁷ ´ 10^-20 =  10^{7 + (-20)} = 10 ^-13

For division,  = 10ⁿ ´ 10^-m = 10^n-m

                      e.g. 10⁶ ¸ 10⁴ = 10^6-4 = 10²

                      10³ ¸ 10^-7 = 10^3-(-7) = 10¹⁰ etc.

Table 2 : Multiples of Ten and their nomenclature in SI.

Prefix	Multiple	Name	Symbol	Example
Peta	1015	Quadrillion	P	1 petametre = 1 pm = 1015m
tera	1012	Trillion	T	1 terahertz = 1 THz = 1012Hz
giga	109	Billion	G	1 gigahertz = 1 GHz = 109 Hz
mega	106	Million	M	1 megawatt = 1 MW = 106 W
kilo	103	Thousand	k	1 Kilogram = 1 Kg = 103g
hecto	102	Hundred	h	1 hectometre = 1 hm = 102m
deca	10	Ten	da	1 decanewton = 1 da N= 10N
deci	10–1	Tenth	d	1 decilitre  = 1 dW = 10-1W
centi	10–2	Hundredth	c	1 centimetre = 1 cm = 10-2m
milli	10–3	Thousandth	m	1 milliampere = 1 mA = 10-3A
micro	10–6	Millionth	m	1 microvolt = 1mV = 10-6V
nano	10–9	Billionth	n	1 nanosecond = 1ns = 10-9s
pico	10–12	Trillionth	P	1 Pico farad = 1 PF = 10-12F
femto	10–15	Quadrillionth	F	1 femtometre  = 1 fm = 10-15m

Table 3: Symbols, units and dimensions of some important physical quantities.

Name of quantity	Symbol	Name of unit	Symbol of unit
Area	A	meter2	m2
Volume	V	meter3	m3
Velocity, speed	u	meter/second	ms–1
Acceleration	a	meter/second2	ms–2
Momentum	P	Kilogram meter/second	kg ms–1
Force	F	Newton	N
Work	W	Joule	J
Power	P	Watt	W
Energy	E	Joule	J
Density	r	kilogram/meter	kgm–3
Pressure	P	Pascal	Pa
Wave length	l	Meter	m
Frequency	f	Hertz	Hz
Co-efficient of expansion	a,b,g	Per Kelvin	K–1
Quantity of heat	Q	Joule	J
Heat capacity	C	Joule/Kelvin	J K–1
Specific latent	l	Joule/kilogram- Kelvin	Jkg–1 K–1
Heat Thermal conductivity	K	watt/ meter kelvin	Wm–1K–1
Luminous intensity	l	Candela	cd
Luminous flux	j	Lumen	lm
Illumination	E	Lux	lx
Power of a lens	P	Dioptre	d