Biology

LIPIDS AND NUTRITION

Lipids can be defined as molecules, synthesized by biological systems, which have , as a major part of their structure, long aliphatic hydrocarbon chains that may be branched or unbranched, may form carbocyclic rings and may contain unsaturated linkages.

Lipids have been matter of health concern in human beings.

There are several reasons for it:

v High prevalence of cardiovascular disease (CVD) and most of the lipid chemists have associated this with high consumption of fat especially saturated fatty acid (SFA)

v Obesity

v Thus the widespread desire to reduce fat in the diet has given rise to low and reduced fat products.

v Nevertheless fats provide a concentrated source of energy and have their important place in the diet.

v Lipids in human diet are derived from storage and structural lipids of plants and animals.

v More than 90% of dietary lipids are triacylglyceols originates from adipose tissue of animals and plant seed oils.

Dietary fats may be divided into two types.

Dietary fats

Visible fats Invisible or hidden fats

They are fats consumed as such They are fats present as

eg. butter, ghee, oils,etc. part of other food item

eg. fat incorporated in

baked foods, pastries, etc

The following table shows the percentage fat content of some foods.

TABLE - 1

Fat content of some foods

Foods % Fat

Cooking oils 100

Lard 99

Butter 82

Margarine 81

Peanuts, roasted 49

Cream 48

Cheese 34

Chocolate, milk 30

Beef, average 24

Cream, Single 21

Herring 14

Eggs 11

Chicken 4.3

Milk, Full cream 3.8

Milk, semi-skimmed 1.7

Cod 0.7

Ques: How much fat does a man need?

Ans: Fats constitute approximately 34% of energy in the human diet. Fats are energy-rich and provide 9 Kcal of energy per gram.

Health professionals say 22 kg/capita / year as against the present consumption of fats in our country - about 8.8 kg/ capita / year. In industrialized nations, it is 26Kg / capita / year.

Nutritional contributions of various food lipids

Lipids constitute a heterogeneous group of compounds of biochemical importance. The following general classification of lipids in based on the chemical nature.

Lipids

1) Simple Lipids

Triacylglycerols (TAG) or triglycerides or neutral fats:-

Esters of fatty acids with glycerol.

Structure of TAG

Function:- TAG are the storage form of lipids in the adipose tissue. The energy value of TAG to body is 38 KJ for one gram compared with about 17 KJ for proteins and 16 KJ for carbohydrates.

2) Waxes

They are esters of fatty acid with high molecular weight alcohols, eg., triacontanyl palmitate, the major component of beeswax. It is an ester of palmitic acid with the alcohol, triacontanol.

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