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Practical
Advice
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Lipids are a group of naturally occurring substance characterized by their insolubility in water, greasy feel and solubility in some organic
solvents. They occur in plant and animal kingdoms. They
are stored in adipose tissues. In normal human beings, adipose tissue constitutes about 10 to 15 per cent of the body
weight which increases up to 30 per cent in obese persons. |
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Classification
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- Simple lipids
- Oils: esters of fatty acids and glycerol.
- Fats: esters of fatty acids and glycerol.
Saturated fats = carbon molecules + hydrogen molecules
Unsaturated fats = Carbon molecule without hydrogen
molecule
- Compound lipids
- Phospho-lipids: these contain phosphoric acid and a nitrogenous base in addition to fatty acids and glycerol. e.g. Lacithin and
cephalin.
- Glyco-lipids: these contain carbohydrates in
combination with fatty acids and glycerols. e.g. corrosives .
- Waxes: These are esters of fatty acids and a long chain
of aliphatic alcohol.
- Derived lipids: These include sterols, fatty acids and alcohols.
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Cholesterol
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Cholesterol is an animal
sterol. The white matter of the brain contains about 4.5 cent and grey matter 1.0 per cent of cholesterol on
a fresh weight basis. Large amounts of cholesterol are also present in sebum secreted by the sebaceous glands. The blood of normal human beings contains 150-250 mg/100
ml of cholesterol.
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Essential Fatty Acids (EFA)
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Linolenic, and arachidonic acids are found to be highly effective in promoting
growth. Hence, they are called 'Essential Fatty Acids'.
Its deficiency leads to perianal irritation and skin changes such as dryness, etc, within a few
weeks.
Essential fatty acids also play critical roles in other body functions and structures. They are transformed into regulatory compounds known as
prostaglandin, and both the prostaglandin's and essential fatty acids are important in a host of bodily functions.
Essential fatty acid
supplements are highly useful in treating cardiovascular
diseases, including high cholesterol levels and high blood
pressure, allergic and inflammatory conditions, including psoriasis and
eczema, autoimmune diseases like multiple sclerosis, lupus and cancer.
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EFA content of oils
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Rich sources
- Sunflower seed
- Safflower seed
- Soybean
- Sesame
- Cottonseed oils
Good sources
- Mustard
- Groundnut oils
- Egg yolk fat
Poor sources
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Essential Fatty Acids are important because they:
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- Regulate steroid production and hormone synthesis
- Regulate pressure in the eye, joints, and blood vessels
- Regulate response to pain, inflammation, and swelling
- Mediate immune response
- Dilate or constrict blood vessels
- Regulate collateral circulation
- Direct endocrine hormones to their target cells
- Regulate the rate at which cells divide (mitosis)
- Maintain the fluidity and rigidity of cellular membranes
- Are necessary in kidney function and fluid balance
- Prevent blood cells from clumping together
(conglomeration) the cause of
plaque and blood clots, precursors of stroke
- Mediate the release of cellular pro-inflammatory substances that may trigger allergic conditions
- Are primary energy source for heart muscles
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Fats
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Saturated fats are
typically animal fatlike butter, lard and tallow. They are
semi-solid to solid at room temperature. In contrast,
unsaturated fats are typically liquid at room temperature
and are therefore often referred to as oils. Most
vegetable oils contain primarily unsaturated fats. |
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Functions of fat
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- Fats are essential for the absorption of vitamins A, D, E, K, and especially
pro vitamin A present in foods of vegetable origin;
- Fats contain essential fatty acids, viz., linoleum, linolenic and arachidonic acids which are essential for maintaining normal
health of tissues ;
- Fats help to reduce the bulk of the diet as starchy foods absorb lot of water during cooking;
- Fats improve the palatability of the diet and give satiety value, i.e. a feeling of fullness in the stomach
- Fats are essential for utilization of galactose present in lactose;
- Phosphatides and other complex lipids are essential constituents of nervous tissue; and
- Fats are deposited in the adipose tissue and these deposits serve as a reserve source of energy during starvation.
Further adipose tissues function like insulating material against cold and physical injury.
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Fat Requirements
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Approximate fat requirements of different age groups are as
follows:
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Per cent total calories from fat |
| Normal adults, expectant and nursing mothers. |
10-15 |
| Children and adolescents (2-18 years). |
15-20 |
| Infants
(from birth to 1 year) |
25-30 |
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