Nutrients are the “chemical components of food that are capable of performing specific functions related to body’s ability to work, grow, develop and maintain good health when supplied in appropriate amounts.” A diverse diet, i.e. a diet which contains a variety of food items from different food groups can provide us many different nutrients which are needed to perform important functions in the body.
Nutrients can be broadly classified as Macronutrients and Micronutrients – based on the amount in which they are required by our body. Both macronutrients and micronutrients are extremely important for our body as each nutrient has specific roles to play. Carbohydrates, protein, fat and water are considered to be macronutrients, needed by our body in quantities ranging from few grams to kilograms.
Sources of Fat:
Cooking Oil, Ghee, Butter, Fatty Meat
Lipids are a heterogenous group of substances including fats, oils and fat-like substances that are greasy in texture, and soluble in organic solvents. Lipids are concentrated sources of energy in our diet. They are the second largest contributors to energy intake, providing 20 - 30% of the total energy intake. Lipids in our diet are mostly fats (or triglycerides), followed by phospholipids and cholesterol esters. Fats are highly complex compounds composed of carbon, hydrogen & oxygen. They are present in nearly all the foods that we eat, adding a special taste & flavor to the food. Each gram of fat provides 9 kcal. Fatty Acids are the main constituents of all lipids.
Types of Fatty Acids
Fatty acids can be classified in various ways as follows:
1. Based on the degree of saturation
As we have mentioned earlier that fatty acids are the main constituent of fats. Saturation here means that whether the fatty acids contain carbon –carbon double or triple bonds. The fatty acids are classified into two types of fatty acids based on saturation.
· Saturated fatty acids – have no double or triple bonds between the carbon atoms. Oils and fats with saturated fatty acids are solid at room temperature e.g. Ghee, butter, palm kernel oil, coconut oil.
· Unsaturated fatty acids – have one or more double bonds between the carbon atoms.
Ø Monounsaturated fatty acids (MUFA) – have a single double bond in between the carbon atoms e.g. Oleic Acid present in palmolein, groundnut oil, olive oil, sesame oil,cottonseed oil, red palm oil, mustard oil etc.
Ø Polyunsaturated fatty acids (PUFA) – have two or more double bonds between the carbon atoms. Sunflower oil, corn oil & safflower oil are rich sources of PUFA.
Trans fatty acid - An unhealthy isomer, made during the process of hydrogenation of oils. Vanaspati is an example of hydrogenated fat. The naturally occurring isomer of unsaturated fatty acids is the cis form.
2. Based on chain length
Based on the length of the carbon chain, fatty acids can be classified as short, medium and long chain fatty acids.
• Short chain fatty acids are usually less than 6 carbon atoms in length. Examples include butyric acid found in milk fat, ghee and butter. These are rapidly digested and can be directly absorbed from the intestines into the blood circulation.
• Medium chain fatty acids contain between 6 and 10 carbon atoms. Examples include caproic, caprylic and capric acids present in milk fat and also coconut oil and palm, kernel oil, which is considered to be a rich source of medium chain fats. These are also rapidly digested and directly absorbed from the intestines into the blood circulation.
• Long chain fatty acids have 12 or more carbon atoms. These include lauric, myristic, palmitic, stearic, oleic, linoleic and linolenic acids. These are found in all the vegetable oils we use for cooking. Most fatty acids present in animal tissues contain 16-26 carbon atoms.
3. Based on Nutritional properties
· Essential fatty acids – are the ones which are very important for growth & development but cannot be synthesized by the body. Linoleic (omega 6) and linolenic acid (omega 3) are the two essential fatty acids. Thus, they must be supplied by the diet. Rich food sources of essential fatty acids are- soyabean, safflower, sunflower,cotton seed oil, and other cooking oils, oily fish like cod, salmon, cereals and legumes, nuts, etc.
· Non – essential fatty acids – are the ones which can be synthesised in the body & are not required from the diet. Stearic, palmitic & oleic acids are the non-essential fatty acids.
· Fats in our diet can also be classified on the basis of their visibility as:Invisible fats – fats which are a part of foods and hence not visible to the eye for instancethe fat present in fish, milk & milk products, meat, egg, nuts & oilseeds.
· Visible fats – are the added to food during preparation & processing. These are fats that can be seen. e.g. oils, ghee, butter, vanaspati & cream.
Functions of Fats
1.Dietary fat has a very important role to play in our bodies. Fats are the chief source of energy for the body. Excess fat is stored inside the body (in the abdomen, surrounding the organs & laced throughout the muscle tissue) as a reserve of energy to be used in times of need.
2.Fats are concentrated sources of energy. One gram fat provides 9kcal; twice the amount as compared to carbohydrates & proteins. Adding some fat to food increases its energy density, thereby reducing the bulk of the diet. This is especially important for small children who cannot have a large quantity of food at a meal. Example adding some ghee to the dal or kheer served to the small child, willmake it energy dense.
3.Fat is an integral part of the structure of the human body; all body cells contain fat in their cell membranes. Amongst healthy & non-obese men & women; 15-25% of the total body weight is fat.
4.Essential fatty acids and long chain PUFA synthesized from these like EPA, DHA and Arachidonic acid perform vital functions in the body. They lead to formation of other substances in the body which are needed for the regulation of a number of vital functions like blood pressure, blood clotting, immune responses, inflammatory responses and regulation of body temperature, etc. DHA is important for normal development & maturation of the retina of the eye & brain development during the first 1000 days.
5.The stored fat acts like an insulator preventing the body from losing heat easily, thus helping to regulate body temperature.
6.Adipose tissue provides a protective cushioning/ padding around the delicate internal organs of the body such as liver, heart & kidneys.
7.It keeps the gastrointestinal tract lubricated helping in smooth movement of food.
8.Fat provide higher satiety value to the meals as it reduces gastric motility, meaning that the movement of the ingested food out of the stomach slows down thereby giving a feeling of fullness for a longer time.
9.Dietary Fat is required for the absorption of fat soluble vitamins – A, D, E and K. A zero fat diet is considered unhealthy.
10. Fat provides variety & flavour to the food thereby increasing the palatability of the food.
Food Sources of Fats:
Health Significance of Fats
Consuming the right combination of fats & oils in appropriate quantities is important. Ideally calories from fat should be between 20-30% of the total calories, with less than 10% calories coming from saturated fats. Eating too little fat can result in poor absorption of fat soluble vitamins (Vitamins A, D, E & K) as well as overdependence on carbohydrates to provide the energy resulting in a very bulky diet. Unsaturated fatty acids like PUFA and MUFA help to decrease the risk of heart diseases by lowering total cholesterol and LDL (Bad) cholesterol levels. Omega 3 fatty acids prevent inflammation and accumulation of fatty material in blood vessels thus protecting against heart diseases. They also prevent thrombosis or clotting of blood thus reducing the risk of strokes.
On the other hand, excessive intake of fat can lead to weight gain & obesity. There is increased risk of cardiovascular diseases and certain types of cancers. Excessive consumption of saturated fatsraises the total and LDL cholesterol levels. They have also been shown to contribute to insulin resistance. Hence, they increase the risk of heart disease and diabetes. Trans fats also increase the risk of heart disease by increasing LDL cholesterol, decreasing HDL (Good) cholesterol, increasing inflammation and insulin resistance in the body.
No comments:
Post a Comment