Fats have been a subject of controversy. In this series, fats and their role in diseases will be enumerated. In this post, basic concepts about fats will be discussed.
In our day to day life, fats are available in two basic forms:-
(a) Visible fats like butter, ghee, seed oils like sunflower, mustard etc. Daily intake of 20-50 gm per day of visible fats is recommended.
(b) Invisible fats. These are integral to a food. Milk and milk products, meat, eggs, grains, pulses etc have fats integral to their structure.
Chemical Composition of Fats
Dietary fats and oils are compound of fatty acids and glycerol. Fats are the warehouse of energy in the body. We have often heard about Triglycerides (TG). TG are storage and transport form of fats in the body. The structural fats (cell wall, membrane, tissue) and milk fats are made of triglycerides, phospholipids and cholesterol esters.
Fats can be classified according to presence of double bond sites in the molecule of parent fatty acid. Based on presence of double bonds, three types of fats or fatty acids are recognized as under:- (Lets revise our X class knowledge).
(a) Saturated Fatty Acids (SFA) or Saturated fats. SFA are solid at room temperature. They have been wrongly labelled as villains of heart, since consumption of saturated fats increases LDL (an alleged bad cholesterol). Except for coconut oil and palm oil (which are plant in origin), all saturated fats are mainly found in foods of animal origin only like meat, milk and milk products, eggs, butter, ghee etc. Unsaturated fats can be converted to saturated fats by hydrogenation. This product is called vanaspati ghee or dalda in common parlance.
(b) Unsaturated fatty acids or fats. Unsaturated fatty acids are liquid at room temperature. They are of two types :-
(i) Monosaturated fatty acids or MUFA present in olive oil and ground nut oil.
(ii) Polyunsaturated fatty acids or PUFA are found in sunflower oil, safflower oil, rice bran, cotton seed oil, mustard, soyabean oil, sesame oil etc. PUFA is a popular term and PUFA are widely believed to be protective against heart diseases. PUFA have been further classified into two groups as under :-
(a) N-6 or omega 6 fatty acids. These have double bonds at 6th position. Example of Omega-6 oils are sunflower oil, safflower oil, rice bran, cotton seed oil, soyabean and corn oil. Linoleic acid (LA) and Arachidonic acid are two essential Omega-6 fatty acids
(b) N-3 or Omega-3 fatty acids. Now a days there is a revised interest in N-3 or omega 3 fatty acids. There are three main N-3 PUFA. Two from animal sources (EPA & DHA) and one from plant sources (ALA).
(i) Animal Sources. EPA (eicosapentoic acid) & DHA (docosahexaenoic acid) are N3 fats present in animal sources. Fish and fish oils, meat and eggs are rich in EPA & DHA. Fish feeding on algae and animals grazing grass will be rich in EPA/DHA. Animal raised in farms with commercial feeds of grains will have more N-6 PUFA than N-3.
(ii) Plant Sources. ALA (Alpha linolenic acid). Mustard oil has maximum N-3 PUFA. Other rich sources are fenugreek seeds, black gram, flax seeds, chia seeds, walnuts, wheat and rajma. Plant sources have alpha linolenic acid (ALA) which is converted to eicosapenenoic acid (EPA) and docosahexaneoic acids (DHA) in body and brain. Only a small fraction of ALA is converted to EPA & DHA, but recent studies indicates that this conversion though small is adequate for day to day brain functions. For optimal brain functions, it is important for vegetarians that the food should be rich in ALA, for so that it can be converted to EPA & DHA adequately.
There are three fatty acids or fats which must be supplied through diet. These are called essential fatty acids (EFA). Arachidonic acid (N6), Linoleic acid (N6) and Linolenic acid (N3). In plants sources linolenic acid is present as ALA. Deficiencies of these fats leads to number of health problems.
For good health, the ratio of N6/N3 should be around 0.8 to 1, which means that N3 intake should be equal to N6 intake, if not higher. We should consume more N-3 fats and reduce our consumption of N6 oils. Unfortunately in our day to day life, we consume more N6 fats in form of sunflower oils, rice bran oils or soyabean oil. Due to misinformation, traditional oils of India; Mustard oil in north, peanut oil in west and coconut oil in South India has been replaced by sunflower oil, which is rich in N6 and pro-inflammatory. A rise in heart diseases in India may be linked to N6 oils.
Fatty Acid Composition
Fatty acid composition of commonly used fats in India is given in my previous post. Cold pressed oils are best for maximum benefits of PUFA oils.
Role in Body
Though fats has been villain of nutritional science, they are components of cell membranes and play an important role in synthesis of hormones. They help in immune functions, in absorption of fat soluble vitamins (like Vitamin A, D & E) and provide support to visceral organs. Fats are body warehouse of energy. One gm of fats gives 9 calories (one gm of carbs or protein give only four calories). People who consume minimal or no fats may suffer from deficiency of fat soluble vitamins.
Take home message
Your food must be rich in N3 PUFA. Include N3 rich food in your diet