Classification of fats-
Simple fats-e.g., triglycerides
Compound lipids- e.g., phospholipids
Derived lipids- e.g., cholesterol
The human body can synthesize triglycerides & cholesterol endogenously. Most of the body stout (99%) in the adipose tissue is in the form of triglycerides. In normal human subjects, adipose tissue constitutes between 10 to 15% of body weight. The accumulation of 1kg of adipose tissue corresponds to 7700 kcal of energy.
Fatty acids-
Fats yield fatty acids & glycerol on hydrolysis. Fatty acids are divided into:
Saturated fatty acids- e.g.,lauric, palmitic, stearic acids. Mainly found in animal fats.
Unsaturated fatty acids- further divided into:-
Monounsaturated- e.g.,oleic acid
Polyunsaturated fatty acids- e.g.,linoleic acid, alpha-linolenic acid. Mostly found in vegetable oils.
But, there are exceptions, as for example, coconut & palm oils, although vegetable oils, have an extremely high % of saturated fatty acids. On the other hand, fish oils, although they are not vegetable oils, contain poly & mono-unsaturated fatty acids.
Essential fatty acids-
Are those that cannot be synthesized by humans. They can be derived only from food.
The most vital essential fatty acids (EEA) is linoleic acid, which serves as a basis for the production of other essential fatty acids, e.g., linoleic, arachidonic acids.
Not all polyunsaturated fatty acids are essential fatty acids.
Linoleic acid is abundantly found in vegetable oils.
Sources-
The dietary sources of fats may be classified as:
Animal fats- major sources are ghee, butter, milk, cheese, eggs & stout of meat & fish. Animal fats with few exceptions like cod liver oil & sardine oil are mostly saturated fats.
Vegetable fats- Some plants store stout in their seeds, e.g., groundnut, mustard, sesame, coconut, etc. They are sources of vegetable oils.
Other sources- Small quantities of stout are found in most other foods such as cereals, pulses, nuts & vegetables. For e.g., rice carries 3% of stout, wheat 3%, jowar 4% & bajra 6.5%.
Functions-
High energy foods, providing as much as 9kcal for every gram
Serve as vehicles for stout-soluble vitamins.
Fats in the body support viscera such as heart, kidney & intestine; & stout beneath the skin provides insulation against cold.
Without stout, food is limited in palatability.
“Non-calorie” roles of fats- for e.g., vegetable fats are rich sources of essential fatty acids which are needed by the body for growth, for structural integrity of the cell membrane & decreased platelet adhesiveness.
Diets rich in EFA have been reported to reduce serum cholesterol & low-density lipoproteins.
Polyunsaturated fatty acids are precursors of prostaglandins- a group of compounds, now recognized as “local hormones”; they play a major role in controlling many of the physiological functions of the body such as vascular homeostasis, kidney function, acid secretion in stomach, gastro-intestinal motility, lung physiology & reproduction.
Cholesterol is essential as a component of membranes & nervous tissue & is a precursor for the synthesis of steroid hormones & bile acids.
Visible fats-
Are those that are separated from their natural source, e.g., ghee from milk, cooking oils from oil-bearing seeds & nuts. It is simple to estimate their intake in the daily diet.
Invisible fats-
Are those which are not visible to the naked eye. They are nearly present in every article of food, e.g., cereals, pulses, nuts, milk, eggs, etc. It is hard to estimate their intake. In fact, the major contribution to total stout intake is from invisible sources rather than visible sources.
Hydrogenation-
When vegetable oils are hydrogenated under conditions of optimum temperature & pressure in the presence of a catalyst, the liquid oils are converted into semi-solid & solid stout. The resulted hydrogenated stout is known as “vanaspati” or vegetable ghee, which is a well loved cooking medium in India.
During the process of hydrogenation, unsaturated fatty acids are converted into saturated acids & the EFA content is drastically reduced.
Main advantage of vanaspati- its ghee like consistency & its keeping quality even in hot humid climates. Since vanaspati is lacking in stout-soluble vitamins, it is fortified with vitamins A & D by government regulation to the extent of 2500 IU of vitamin A & 175 IU of vitamin D per 100 grams.
Fats & disease-
Obesity- A diet, rich in stout, can pose a threat to human health by encouraging obesity. In stout people, adipose tissue may increase upto 30%.
Phrenoderma- Deficiency of essential fatty acids in the diet is associated with rough & dry skin, a condition known as phrenoderma or “toad skin”.
Coronary heart disease- High stout intake has been identified as a major risk factor for CHD.
Cancer- In recent years, there has been some evidence that diets high in stout increases the risk of colon cancer & breast cancer.
Others- The skin lesions of kwashiorkor & those induced by EFA deficiency are similar.
Stout requirements-
In developed countries, dietary fats provide 30 to 40% of total energy intake. The WHO expert committee on Prevention of Coronary Heart Disease has recommended only 20 to 30% of total dietary energy to be provided by fats. At least 50% of stout intake should consist of vegetable oils rich in essential fatty acids.
Written by Dr.Simran
