The Essential Fatty Acids

The Essential Fatty Acids: The term lipid is general term for fat or fat like substances. The lipids are group of naturally occurring substances which are important constituents of our diet, as they possess high energy value. Fat soluble vitamins and several essential fatty acid occurs in food baying good fat content. Any of a large number of oily compounds that are widely found in plant and animal issues and serve mainly as a reserve source of energy.

Esters of fatty acid with alcohol are what are referred to as fats. Fat can also be defined as, “compounds, in which one molecule of glycerol is combined with three molecules of fatty acid. Fats are insoluble in water and are highly concentrated source of energy”.

Simple Lipids

These are esters of fatty acid with alcohol. They are further classified on the basis of nature of alcohol in the structure:

1. Fats and Oils/Neutral fats/True fats: These are most abundant fats in nature, which are formed by reaction between fatty acid and glycerol. They have greater satiety value than carbohydrates, as they stay in stomach for more time. They are stored in body in form of adipose tissue. In normal man 10-20% of body weight is fat.

2. Waxes: Waxes are not so abundant. They are chemical esters of fatty acid with higher alcohols or alcohols other than glycerol. It occurs in bee wax. In vertebrates, it is secreted by cutaneous gland as protective coating.

Compounds or Conjugated Lipids

Compound lipids are esters of fatty acid with alcohol. But they additionally contain some other substances also.

Example:

1. Phospholipids: Phospholipids possess nitrogen containing base and phosphate group in addition to fatty acid and alcohol.

2 Glycolipids: Glycolipids is such a conjugated lipid which have additional carbohydrate group attached to fatty acid and alcohol.

Derived Lipids

This group includes those lipids which are obtained by hydrolysis of simple or compound lipids and they still retain lipid like properties.

Example: Glycerol, steroid, oleic acid, palmitic acid, all fat soluble vitamins A, D, E, K a included in this group only.

Saturated fatty acid

Saturated fats have all carbon atoms linked by single bond in their structure.

Example: Stearic acid, Palmitic acid

Unsaturated fatty acid

Thefattyacid whose carbon atom are linked by double bonds and have lesser number of hydrogen atoms in the structure.

Example: Oleic acid and linoleic acid.

1. Polyunsaturated fatty acids:

These fatty acids have more than one double bond in their structure.

2. Monounsaturated fatty acids:

These fatty acids contains only one double bond in their structure.

Difference Between Saturated and Unsaturated Fatty Acids

Saturated Fatty Acid Unsaturated Fatty Acid
Its structure has all carbon atoms linked by single bonds. Structure possess one or more double Table single bonds.
It has straight chain structure. It has bend at sites of double bond.
They have higher melting point. Melting point is lower.
These are solid at room temperature. They are liquid at room temperature.
They are mostly of animal origin. They are of plant origin.

Showing Predominant Fatty Acid Present in Commonly Used Oils

Fats/ Oils Predominant Fatty Acid
Coconut Saturated fatty acid
Ghee Saturated fatty acid
Vanaspati Saturated fatty acid
Palm oil Saturated fatty acid + Monounsaturated fatty acid
Olive Same
Ground nut Monounsaturated fatty acid
Mustard Same
Sesame Monounsaturated fatty acid Polyunsaturated fatty acid
Rice bran Same
Cotton seed Polyunsaturated fatty acid
Corn Same
Sunflower Same
Safflower Same
Soyabean Same

Shows the Sources of Types of Fatty Acid

Saturated fatty acid   Monounsaturated fatty acid Polyunsaturated fatty acid
Coconut oil Fish oil   Most vegetable oil
Animal fat   Olive oil Safflower, corn
Peanut oil Canola oil Soyabean, cotton
Butter   Seed, walnut, wheat germ oil

The Essential Fatty Acids | What are the essential fatty acids

Common name Number of carbon atoms Number of double bonds Typical fat source
Saturated fatty acid      
Butyric 4 0 Butterfat
Caproic 6 0 Butterfat
Butterfat 8 0 Coconut oil
Caprylic 10 0 Coconut oil
Lauric 12 0 Coconut oil, palm kernel oil
Myristic 14 0 Butterfat, Coconut oil
Palmitic 16 0 Palm oil, animal fat
Stearic 18 0 Cocoa butter, animal fat
Arachidic 20 0 Peanut oil
Behenic 22 0 Peanut oil
Unsaturated fatty acid      
Caproleic 10 1 Butterfat
Leuroleic 12 1 Butterfat
Myristoleic 14 1 Some fish oils, beef fat
Oleic 16 1 Olive oil, canola oil
Elaidic 18 1 Butterfat
Vacceric 18 1 Butterfat
Linoleic 18 2 Most vegetable oils, especially safflower, corn, soybean, cottonseed
Linolenic 18 3 Soybean oil, canola oil, walnuts, wheat germ oil, flaxseed oil

On Basis of Origin

Plant fat:

As the name suggest they are obtained from plants.

Animal fat:

These are obtained from animals.

Showing difference between Plant and Animal fat

Plant Fat   Animal fat
Plant fat have higher percentage of unsaturated fatty acid. Animal fat have greater concentration of saturated fatty acid.
They are liquid at room temperature. They are usually solid at room temperature.
They can be stored for longer period. They undergo spoilage or rancidity very fast.
They do not possess cholesterol. They have cholesterol.
Sources: Seeds and fruits. Sources: Liver and Bone marrow region, etc.
Predominant fatty acid in plant fat is oleic and linoleic acid. Predominant fatty acid in animal fat is plamitic acid and stearic acid.
Example: Olive oil, sunflower oil, coconut oil etc.   Example: Butter, Desi ghee, etc.  

Classification on Basis of Nature

Showing Clear Difference Between the Visible and Invisible Fat

Visible Fat  

Invisible Fat  

It is that fat which can be seen with naked eyes and can be easily derived out from food. It is not visible part of food and cannot be easily extracted out.
These are mainly triglycerols. It is usually hidden fat present in membrane of plants and animals, i.e. mainly phospholipids, glycolipids and cholesterol.
Easier to keep check on amount of visible fat being consumed. As this part of fat is not visible. So, this part is difficult to control.
Example: Animal fat like Butter, Desi ghee, vegetable oil, etc. Fat content of food products like milk and milkproducts, poultry products, nuts, cereal, pulses etc.  

Classification on Basis of Need

Essential Fatty Acid

Essential fatty acid are those which body cannot produce itself. So, they must be consumed in diet. Deficiency of essential fatty acid may lead to deficiency disorder known as phrynoderma. Body require them to perform several important functions.

Example: linoleic acid, linolenic acid and arachidonic acid.

Non-Essential Fatty Acid

Group of those fatty acid which can be produced by body itself. They are not essential to be supplied in food.

CALORIC VALUE

Fat is one of such a nutrient which is the most concentrated source of energy. It provides double the amount of energy as compared to proteins and carbohydrates. On complete oxidation of fat to carbondioxide and water, approximately 9 kcal of energy is produced.

RECOMMENDED DIETARY ALLOWANCES (RDAS)

Fat is one of such macronutrient whose intake above certain level can prove to be very detrimental to our health. As it is related to several cardiovascular diseases. Daily intake of fat should be well below 50 g/day. This 50 g/day amount include both invisible and visible fat. Studies have shown that Indian diet contains approximately 10-15% of invisible fat. So, recommended dietary allowances for visible fat remains to be 15-20 g/day WHO expert committee recommendation says 20-30% of total energy should come from fats.

Below is table showing RDAs for Indian recommended by ICMR.

Group Visible fat g/day
Man 20
Woman 20
Pregnant lady 30
Lactating lady 45
Children 1-9 yrs 25
Boys and Girls:
• 10-12 yrs
• 13-15 yrs
• 10-18 yrs
22
22
22  

Shows the Sources of Types of Fatty Acid

Saturated fatty acid   Monounsaturated fatty acid Polyunsaturated fatty acid
Coconut oil Fish oil   Most vegetable oil
Animal fat   Olive oil Safflower, corn
Peanut oil Canola oil Soyabean, cotton
Butter   Seed, walnut, wheat germ oil

SOURCES OF FAT

The sources from which we get fat (both visible and invisible fat) are:

1. The visible fat comes from butter, ghee, hydrogenated oil, cooking oil. T

2. The invisible fat is available in fish, meat, poultry, milk and milk products, nuts, and oilseeds, cereal and pulses. =ruits and vegetable are poor sources of fat.

Fat content of food

Food Stuff Fat g/100g
Butter 81
Ghee 100
Hydrogenated oil 100
Cooking oil 100
Milk BuffaloCow   6.5 4.1
Egg hen 13.3
Almonds 58.9
Coconut (Dry) (Fresh) 62.3 41.6
Soyabean 19.5

FUNCTIONS OF FAT

1. Source of energy: Fat is the most concentrated source of energy, as it provides 9 kcal of energy on complete oxidation to carbondioxide and water.

2. Palatability: The presence of fat in food, makes it more palatable, as it provides tex-ture and flavour to food.

3. Carrier: Fat acts as carrier of several important dietary component like fat soluble vi-tamins A, D, E and K. Anything that interferes with absorption of fat also disrupts the supply of fat soluble vitamins.

4. Satiety value: Fat has longer transiet time as compared to other nutrients. So, fat leaves the stomach relatively slowly. Hence, delays the onset of hunger and contrib-utes to feeling of satiety after meal.

5. Energy reserves: Fat is stored in the body in form of specialised cell called adipocytes, which forms adipose tissue. Excessive fat reserves makes the person overweight.

6. Protein sparing action: Like carbohydrates primarly function of fat is to provide en-ergy, so together with carbohydrate it performs that function. Hence it spares the pro-tein for its body building primarly function.

7. Cell membrane structure: Fat forms the component of cellular membrane. Both outer and internal membrane possess fat in their structure.

8. Body shape: Subcutaneous fat keeps skin firm and helps in rounding off contour of the body.

9. Components of pigment: Fat is present in several plant and animal pigments like chlorophyll, carotenoids, rhodopsin and other visual pigments.

10. Regulating body function: Fats like Omega-6 and Omega-3 unsaturated fatty acid, act as precursor of hormone like substances eicosanoids (prostaglandins, prostacy-clins, etc.). Fat plays important role in formation of certain hormones such as adrenal cortical and sex hormones.

11. Insulation: Fat get deposited beneath skin as subcutaneous fat, to act as insulating material by preventing heat loss.

12. Protective role: Fat also plays an important role as protector. It forms waxy coating in animal fur and plants leaves and fruits. So, check heat loss in animals especially in colder region and keep check on transpiration in plants. In humans fat forms protec-tive covering around vital organs like kidney, heart, eyes, etc. So, act as shock absorb-ing cushion for internal organs.

13. Other function: Essential fatty acid has certain other important role, else than ac as concentrated source of energy. Essential fatty acid are linoleic, linolenic and  arachodonic acid:

a. These are involved in growth and development.

b. It has shown positive effect in reversing cardiovascular diseases.

c. Omega-3 has been found protective against breast and colon cancer.

DIGESTION

Digestion is the process, in which complex molecules are broken down into simple  absorbable form.

Steps Involved in Fat Digestion 

Salivary Phase (In mouth)

Here no major digestion of fat takes place. Because food stays in mouth for very short time. Mainly mechanical breakdown of fat takes place here. Saliva contain lingual lipase fat digesting enzyme. But breakdown is negligible.

Gastric Phase

Digestion of fat starts in stomach. Stomach contain enzyme called gastric lipase.

But even this conversion of fats to diglyceride and fatty acid is nearly negligible, be-cause enzyme gastric lipase is sensitive to free acid and is soon destroyed as acidity in-creases. This enzyme only acts for a short while till acidity in not high.

Intestinal Phase

Here food meets with three juices i.e., bile, pancreatic juice and intestinal juice.

Bile: Contain no enzymes. But it prepares fat for digestion, as it brings about emulsification of fat, i.e. little fat droplets are formed by breaking up larger ones. Bile salts get associated with small fat droplets and form emulsified droplets. This increases surface area for better action of fat splitting enzyme. Bile also activates lipase and also helps in absorption of fat and fat soluble vitamins.

Pancreatic Juice: The main digestion of fat takes place in small intestine. Pancreatic lipase acts on fat in 3 stages:

Stage 1: Pancreatic lipase hydrolyses triglyceride to diglyceride and glycerol.

Stage 2: Pancreatic lipase now hydrolyses diglyceride

Final stage: In this stage monoglycerids are hydrolysed to fatty acid and glycerol

After complete hydrolysis of fat we get three fatty acid molecule and one glycerol. But still fat digestion is not complete, because digestion of fat is very slow in process and pancreatic lipase does not have enough time to bring about complete digestion.

Intestinal Juice: Intestinal lipase is alkaline in nature. So, it can easily bring about complete digestion of remaining fat. It acts in same ways as pancreatic lipase works.

ABSORPTION

Absorption is the passage of digested food from digestive tract into tissue or blood. The main absorption site is a small intestine. For this villi and microvilli increase the surface area of small intestine.

Body lacks the ability to directly absorb the end product of fat digestion, as they are insoluble in water. Hence product of fat digestion which include long chain fatty acid, monoglyceride, diglyceride combine with bile salts and phospholipids to form water soluble molecular aggregate called micelles.

From these micelles fatty acid, glycerides and fat soluble vitamins A, D, E and K are actively absorbed into intestinal cells. In intestinal cells bile attached to end product of fat Digestion is freed and they recombine to form fats i.e. triglyceride.

Triglyceride forms fine globules called chylomicron. Chylomicron becomes water soluble by acquiring protein coat and it is called as Lipoprotein. Being water soluble it is ashy transported into lymph and blood. Lipoprotein are hydrolysed by blood plasma enzyme and enter cells as fatty acid and glycerol.

STORAGE

Fat is stored in specialized form of cells called adipocyte, which form specialized tissue _led adipose tissue. Excess of fat is stored in liver, adipose tissue, beneath skin, around art and kidney.

METABOLISM

It involves utilization of absorbed fat:

1. Fat which get absorbed into body is broken down into fatty acid and glycerol. Liver then resynthesise fat in accordance to body requirement. So, liver is main organ involved in regulation of fatty acid balance of body and sup-plies fat in accordance to body needs.

2. Fat in absence of carbohydrates act as energy source. Fat is drawn from fat deposit and then passed down to liver.

3. Fat is utilised as building material for cells. Phospholipid is used in formation of cellular material.

4. Fat is also involved in thermal regulation as subcutaneous adipose tissue prevent heat loss.

5. If excessive oxidation of fatty acid for energy production occurs especially in f and diabetic person, then intermediatery product ketone bodies are formed.

CHOLESTEROL

Cholesterol is a type of sterol, i.e. animal sterol. Sterol are most abundant group of steroids. They do not contain fatty acid in their structure. But have lipids like properties

Cholesterol occurs in various animal and human tissues. It forms important part of plasma membrane, it is also found in brain, spinal cord, nervous tissue, adrenal gland and egg yolk. It is essential for synthesis of adrenocortical hormones, inactive form of vitamin D, i.e. dehydrocholecalceferol.

Normal Range

Blood contain cholesterol upto 150 to 200 mg per 100 ml.

Sources

Egg yolk, animal products like milk, meat and poultry. If its level increases beyond 200 mg/dl, it becomes risky for heart. As increased level of cholesterol may result in atherosclerosis i.e. narrowing of arteries, which ultimately results in heart attack.

MALNUTRITION

Improper or unbalanced nutrition is a definition of malnutrition. There are two ways to study it:

1. Undernutrition

2. Overnutrition

Undernutrition

It is the condition, in which consumption is lesser than the recommended dietary allowances. Undernutrition of fat is not so common. But if fat gets deficient in diet then it leads to:

1. Hinderance in absorption of fat soluble vitamins A, D, E and K.

2. It leads to deficiency of essential fatty acid.

Deficiency of Essential Fatty Acid

There is no common name for the deficiency of essential fatty acid. But, its deficiency pro-duces several adverse affects, which are as follow:

1. Adverse effect on reproductive system and lactation

2. Leads to growth retardation

3. Affects energy production

4. Causes water imbalance

5. Affects integrity of cell membrane

6. Causes permanent learning defects

Infants fed on formulas low in linoleic acid, one of essential fatty acid for three months develop dry, thick and flaking skin and also sign of growth retardation. All these clinical symptoms disappear as soon as linoleic acid is given to infant. Recent researches have shown that if preterm infant is fed with formulas low in omega 3 fatty acid. It leads to abnormalities in vision.

Phrynoderma or Toad Skin

Phrynoderma is a skin disorder, in which skin appears to be rough like toad skin. Horny popular eruption occurs on posterior and lateral parts of limbs, back and buttocks. It be improved by consumption of food having essential fatty acid along with vitamin A, Complex group.

Overnutrition

Obesity

Fat which is concentrated source of energy, if consumed in excess, get deposited in form of adipose tissue. This leads to weight gain. Obesity is itself a cause of several disorders like high blood pressure, diabetes, heart ailments etc.

Hypercholesterolemia

Excessive consumption of fat in diet increases cholesterol level in the body. This cholesterol gets deposited in blood vessels, causing atherosclerosis. This results in narrowing and hardening of blood vessles. Hence causing problem like high blood pressure.

Excess of saturated fat containing products like butter, ghee, hydrogenated veg oil, red meat and egg, etc., makes the surface of arteries irregular and some time clot formation occurs i.e. thrombosis. So, thrombosis, resulting in narrowing of artery may sometime ultimately it leads to heart attack.

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