Explain the classification, sources, function, requirements and deficiencies of fats.

Fats are basically subgroup of lipids and are known as triglycerides. These oily substances are  found beneath the skin and surrounding the organs are the primary energy depots of animals. They are highly complex compounds composed of carbon, hydrogen & oxygen. They are present in nearly all the foods that we eat, adding a special taste and flavor to the food.

Classification:

A fat molecule consists of two kinds of parts: a glycerol backbone and three fatty acid tails. Fatty acids can be classified in various ways as follows:

Based on the degree of saturation : 

1. Saturated fatty acids – have no double or triple bonds between the carbon atoms. Oils and fats with saturated fatty acids are solid at room temperature e.g. Ghee, butter, palm kernel oil, coconut oil

sources:

It is mostly in animal foods, such as milk, cheese, and meat. Poultry and fish have less saturated fat than red meat. Saturated fat is also in tropical oils, such as coconut oil, palm oil, and cocoa butter. You'll find tropical oils in many snacks and in nondairy foods, such as coffee creamers and whipped toppings. Foods made with butter, margarine, or shortening (cakes, cookies, and other desserts) have a lot of saturated fat. Saturated fat can raise your cholesterol. 

2. Unsaturated fatty acids – have one or more double bonds between the carbon atoms.

i.  Monounsaturated fatty acids (MUFA) – have a single double bond in between the carbon atoms e.g. Oleic Acid present in palmolein, groundnut oil, olive oil, sesame oil, cottonseed oil, red palm oil, mustard oil etc.

ii. Polyunsaturated fatty acids (PUFA) – have two or more double bonds between the carbon atoms. Sunflower oil, corn oil & safflower oil are rich sources of PUFA.

• Omega-3 fatty acids are found in foods from plants like soybean oil, canola oil, walnuts, and flaxseed. They are also found in fatty fish and shellfish as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Salmon, anchovies, herring, sardines, Pacific oysters, trout, Atlantic mackerel, and Pacific mackerel are high in EPA and DHA and lower in mercury. A healthy diet includes 8 ounces or more of these types of fish a week, averaging 250 mg a day of these omega-3 fatty acids.footnote2
• Omega-6 fatty acids are found mostly in liquid vegetable oils like soybean oil, corn oil, and safflower oil.

3. Trans fatty acid - An unhealthy isomer, made during the process of hydrogenation of oils. Vanaspati is an example of hydrogenated fat. The naturally occurring isomer of unsaturated fatty acids is the cis form.

Sources: 

• Processed foods.
• Snack foods, such as chips and crackers.
• Cookies.
• Some margarine and salad dressings.
• Foods made with shortening and partially hydrogenated oils

Based on Nutritional properties: 

Essential fatty acids – are the ones which are very important for growth & development but cannot be synthesized by the body. Linoleic (omega 6) and linolenic acid (omega 3) are the two essential fatty acids. Thus, they must be supplied by the diet. Rich food sources of essential fatty acids are- soyabean, safflower, sunflower,cotton seed oil, and other cooking oils, oily fish like cod, salmon, cereals and legumes, nuts, etc.

Non – essential fatty acids – are the ones which can be synthesised in the body & are not required from the diet. Stearic, palmitic & oleic acids are the non-essential fatty acids.

· Fats in our diet can also be classified on the basis of their visibility as:

Invisible fats – fats which are a part of foods and hence not visible to the eye for instance. the fat

present in fish, milk & milk products, meat, egg, nuts & oilseeds.

Visible fats – are the added to food during preparation & processing. These are fats

that can be seen. e.g. oils, ghee, butter, vanaspati & cream

Function:

1.Dietary fat has a very important role to play in our bodies. Fats are the chief source of energy

for the body. Excess fat is stored inside the body (in the abdomen, surrounding the organs &

laced throughout the muscle tissue) as a reserve of energy to be used in times of need.

2.Fats are concentrated sources of energy. One gram fat provides 9kcal; twice the amount as

compared to carbohydrates & proteins. Adding some fat to food increases its energy density,

thereby reducing the bulk of the diet. This is especially important for small children who

cannot have a large quantity of food at a meal. Example adding some ghee to the dal or

kheer served to the small child, willmake it energy dense.

3.Fat is an integral part of the structure of the human body; all body cells contain fat in their cell

membranes. Amongst healthy & non-obese men & women; 15-25% of the total body weight

is fat.

4.Essential fatty acids and long chain PUFA synthesized from these like EPA, DHA and

Arachidonic acid perform vital functions in the body. They lead to formation of other

substances in the body which are needed for the regulation of a number of vital functions

like blood pressure, blood clotting, immune responses, inflammatory responses and

regulation of body temperature, etc. DHA is important for normal development &

maturation of the retina of the eye & brain development during the first 1000 days.

5.The stored fat acts like an insulator preventing the body from losing heat easily, thus helping

to regulate body temperature.

6.Adipose tissue provides a protective cushioning/ padding around the delicate internal organs

of the body such as liver, heart & kidneys.

7.It keeps the gastrointestinal tract lubricated helping in smooth movement of food.

8.Fat provide higher satiety value to the meals as it reduces gastric motility, meaning that the

movement of the ingested food out of the stomach slows down thereby giving a feeling of

fullness for a longer time.

9.Dietary Fat is required for the absorption of fat soluble vitamins – A, D, E and K. A zero fat

diet is considered unhealthy.

10. Fat provides variety & flavour to the food thereby increasing the palatability of the food.

Health Significance of Fats:

- Consuming the right combination of fats & oils in appropriate quantities is important. Ideally

calories from fat should be between 20-30% of the total calories, with less than 10% calories

coming from saturated fats. Eating too little fat can result in poor absorption of fat soluble

vitamins (Vitamins A, D, E & K) as well as overdependence on carbohydrates to provide the

energy resulting in a very bulky diet. Unsaturated fatty acids like PUFA and MUFA help to

decrease the risk of heart diseases by lowering total cholesterol and LDL (Bad) cholesterol

levels. Omega 3 fatty acids prevent inflammation and accumulation of fatty material in blood

vessels thus protecting against heart diseases. They also prevent thrombosis or clotting of blood

thus reducing the risk of strokes.

.On the other hand, excessive intake of fat can lead to weight gain & obesity. There is increased

risk of cardiovascular diseases and certain types of cancers. Excessive consumption of saturated

fatsraises the total and LDL cholesterol levels. They have also been shown to contribute to

insulin resistance. Hence, they increase the risk of heart disease and diabetes. Trans fats also

increase the risk of heart disease by increasing LDL cholesterol, decreasing HDL (Good)

cholesterol, increasing inflammation and insulin resistance in the body.