HOW TO USE FATS IN YOUR DAILY DIET
Why do we need fats?
Fats contribute to texture, flavor and taste and increase the palatability of the diet.
Fats are essential for meeting some of the nutritional needs like essential fatty acids (linoleic n-6 and alpha-linolenic n-3) and serve as rich sources of energy.
However, for the growth of young children high-calorific diets are required. This is achieved by inclusion of adequate amounts of fat in their diets as they cannot consume large quantities of bulky cereal - pulse- based diets.
Fats also promote the absorption of the four fat-soluble vitamins (A,D,E and K), impart a feeling of fullness and satisfaction and thus, delay the onset of hunger.
Along with proteins, fats constitute major components of body fluids and cell membranes.
The two essential fatty acids (EFA) namely, linoleic (LA n-6) and alpha- linolenic (ALA n-3) acids (important dietary polyunsaturated fatty acids) are metabolized at various sites in the body to generate a group of biologically-active compounds, which perform several important physiological functions.
Sources of fats
Dietary fats can be derived from plant and animal sources. Fats that are used as such at the table or during cooking (vegetable oils, vanaspati, butter and ghee) are termed as “visible” fats. Fats that are present as an integral component of various foods are referred to as “invisible” fat. Fats, in processed and ready to eat foods are known as hidden fats. The small amounts of invisible fat present in various foods add up to a substantial level in our daily diet
How much visible fat do we need?
The total fat (visible + invisible) in the diet should provide between 20-30% of total calories. The higher fat and EFA requirements during pregnancy and lactation are to meet the requirements of fetus and young infants, in view of their crucial role in physical and neuronal growth and development. Diets of young children and adolescents should contain about 30-50g/day. However, ingestion of too much fat is not conducive to good health.
Chemical components of fat
Fatty acids are the primary constituents of all dietary fats. Based on their chemical nature, the fatty acids are broadly grouped as saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA). Fats from coconut oil, vanaspati, animal fats (ghee and butter) and animal foods like milk, milk products and meat provide saturated fatty acids. The short and medium chain saturated fatty acids present in ghee, butter and coconut oil are easily digested and absorbed and are therefore, good for infants and young children. However, high intake of saturated fatty acids increases atherogenic risk and their intake should be limited in adults.
Oils from sources such as palm, groundnut, cottonseed, sesame and olive are rich in monounsaturated fattyacids as compared to other oils. Linoleic (n-6) and -linolenic (n-3) acids are the simple PUFA, which are present only in plant foods. All vegetable oils (except coconut) are good sources of linoleic(n-6) acid. Soyabean, rapeseed and mustard oils are the only vegetable oils, which contribute significant proportion of alpha-linolenic (n-3) acid. Legumes/pulses mustard and fenugreek seeds and green leafy vegetables are also good sources of a-linolenic (n-3) acid. On the other hand, fish and fish oils provide long chain n-3 fatty acids, which are biologically more active than alpha-linolenic (n-3) acid present in plant foods.
Cholesterol: Cholesterol is present only in foods of animal origin such as milk, meat, shrimp and prawn, but not in plant foods. Vegetable oils do not contain cholesterol. Egg yolk and organ meats such as liver, kidney and brain contain very high amounts of cholesterol. Cholesterol is found in all body cells and plays a key role in the formation of brain, nerve tissue and is a pre-cursor for some hormones and vitamin D. It is synthesized in the body and hence it is not an essential dietary component.
CHOICE OF COOKING OILS
In view of the above, an ideal quality fat for good health is the one which maintains a balance, so as to give a ratio of polyunsaturated/ saturated (PUFA/ SFA) of 0.8-1.0, and linoleic/ a-linolenic (n-6/ n-3) of 5-10 in the total diet. For ensuring this appropriate balance of fatty acids in cereal-based diets, it is necessary to increase the a-linolenic (n-3) acid intake and reduce the quantity of linoleic (n-6) acid obtained from the cooking oil.
Use of more than one source of fat/oil has the added advantage of providing a variety of minor components in the diet. An additional way of increasing alpha- linolenic (n-3) acid intake is to ensure regular consumption of oils and foods rich in alpha-linolenic acid.
(Source – Dietary Guidelines for Indians, NIN)