Few days back, I visited one of my earlier colleague, who is an old heart patient with coronary bypass done. He was also suffering from diabetes. He showed me all his papers and asked me if anything else is required to be done. I asked him about his intake of fats and oils in diet. He told me that ‘My doctor has advised me to take PUFA rich oil and avoid butter or vanaspati ghee. Now I am using refined sunflower oil’. I asked him how much sunflower oil has been advised. He replied ‘the doctor has not informed me about any upper limit of PUFA intake’. This prompted me to write this post about the intake of fats and oils in diet to give you an insight in correct perspective.
In recent times there has been high awareness about the role of fats and oils in our diet. High fat diets increase body weight. High intake of total fat and saturated fats increases blood cholesterol, promote atherosclerosis and clotting of blood (thrombosis). Trans fatty acids in hydrogenated oils increase blood cholesterol. The fat intake has been directly linked to pathological conditions like atherosclerosis, obesity, heart diseases and so on. It is proved that adequate intake of PUFA lowers blood cholesterol. However, there are large number of misconceptions about the use of PUFA. Advertisements in TV gives an wrong impression that PUFA can be taken in any amount by heart patients. Patients often replace vanaspati ghee or traditional cooking oil by refined sunflower oil without reducing total fat intake. PUFA are also not free from its side effects. Prolonged or repeated heating of polyunsaturated fatty acids produce toxic substances like polymerised products, peroxides and free radicals. Excess consumption of PUFA can suppress immune functions and reduce HDL (good cholesterol). On the other hand, some people do not consume fats at all and rely on boiled or roasted foods. These people will eventually suffer due to inadequate fat intake. In this post I will discuss about various types of fats, their role in body and the quantity of fats/oils that should be consumed daily.
Chemical composition of fats
Chemically, fats are a combination of fatty acids and glycerol. Fats & oils have similar chemical structure. Oils are liquid at room temperature. Fats can be classified as saturated and unsaturated. Fatty acids of biological importance are straight chain aliphatic, monocarboxylic acids with an even number of carbon atoms and general formula CH3(CH2)n-COOH, where n varies from 2 to 22 (try to remember chemistry of class X). Saturated fatty acids have only one bond, while unsaturated fats have bonds varying from one covalent bond (monounsaturated) to many covalent bonds (polyunsaturated). Since we all have forgotten our chemistry classes of class X, we will just remember that fats are primarily of two types ; saturated fats and unsaturated fats.
Functions of Fats
Fats are important for various body functions. They are rich source of energy. One gram of fat yield 9 Calories per gm viz a viz proteins and carbohydrates, which give 4 Calories per gm. They are integral part of cell membranes & steroid hormones. Fats play an important role in inflammatory reactions and blood clotting mechanisms. The detailed discussion is not required and is beyond the scope of the post.
Types of Fats: Saturated vs Unsaturated
For functional point of view, we will classify them as saturated and unsaturated fats. Fats and fatty acids will be used synonymously. Saturated fats can be obtained from plant sources (coconut, hydrogenated vegetable oils & palm kernel) and animal sources (butter, desi ghee, fats from animal flesh foods and organ meet). All plants sources oils, (less coconut & palm kernel oil) are predominantly unsaturated. In addition, invisible fats present in cereals, pulses, legumes, roots, tubers, vegetables, spices, fruits and muscles (lean meat) are predominantly unsaturated. Invisible or hidden fats are those fats which are integral part of the food item and not visible. Visible fats are fats extracted from oil seeds (vegetable oils), adipose tissue of animals, milk (animal fats) and fish liver (fish oils). Visible fats are in facts storage fats of plants and animals.
Unsaturated fatty acids are broadly divided into two groups; monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA). We are all aware of the term PUFA. Out of all oils generally used for cooking, coconut, palm kernel, vanaspati & red palm oils are rich in saturated fatty acids. Olive oil, groundnut oil, rape/mustard and sesame are rich in mono-unsaturated fatty acids. Rice bran, cotton seed, sun flower, safflower, soyabean are rich in PUFA. In PUFA group there are two different types of fatty acids; linoleic acid (LA) and alpha linolenic acid (ALA), which are called as essential fatty acids (EFA). These fatty acids cannot be synthesized in body and must be supplied in diet. PUFA have been further divided into two groups; N-6 fatty acids (derived from LA) and N-3 fatty acids (derived from ALA). We can group commonly used oils into three groups:-
Oil with moderate amount of LA/N-6 fatty acids Groundnut, rice bran and sesame
Oil with high LA/N-6 fatty acids Safflower, sunflower, cotton seeds and corn
Oil with high ALA/N-3 fatty acids- Mustard and soyabean
If you have understood that there are three groups of PUFA viz moderate N-6, high N-6 and high ALA (N-3) then half the battle is won and we may proceed further.
How much fats be consumed
An ideal diet should have good quality of fats to induce anti-atherogenic (reduce cholesterol and triglycerides levels in the blood), anti-thrombotic and anti-inflammatory effect which is required for prevention/control of heart diseases and diabetes. The ratio of PUFA/SFA should be of 0.8-1.0 and N-6/N-3 should be 5-10. LA should range 3-7% of total calorie and ALA should not be less 1% of total calories. In a healthy diet not more than 15-30% Calories should be derived from fats. 30% is upper limit for special groups like soldiers, labourers, athletes & body builders etc who perform lots of physical work. Sedentary people should restrict fat intake to 15% of total calories. An adult consuming 2400 Calories requires 40 gm of fat (15% of total Calories). In a typical Indian diet which is primarily cereal based, 20 gm fats are derived from invisible fats in foods. Thus 20 gm or 4 teaspoonfuls of visible fats are needed. Any consumption of fats above 30% of total Calories in diet (from all sources) increases the risk of atherosclerosis & abnormal lipids in the blood. We are all aware that the atherosclerosis is precursor of heart diseases. A heart or diabetic patient should limit fats consumption to 15% of total calorie.
One may ask, how much calorie I should consume per day? One can calculate his calorie requirement by using this method, which is valid for a sedentary person. Measure your weight and calculate body mass index or BMI (Weight (kg) divided by height square (meters). If BMI value is between 18-25 (the normal value), your requirement is 30 Calories per kg per day. If the value is 26-30 (overweight), the requirement is 20 Calories per kg body weight per day. Some adjustments are also required. If you are 50+, then reduce the total Calories by 10% per decade. Ideally 8-10% should come from saturated fats, 5-8% should come from PUFA and rest should come from monounsaturated fats. A person consuming 20 gm of fats should get approximately 2 gm (half teaspoonful) from saturated fats (butter, vanaspati ghee, etc), 2 gm from PUFA and 16 gm from MUFA (groundnut, mustard or olive oil). This dispenses the myth that you can have any amount of PUFA without any problem, which has been erroneously created by TV advertisements. Upper limit of fat should not be exceeded in any case.
Now I will do a sample calculation for a hypothetical person Mr IM Healthy. His age is 52 years. His weight is 70 kg and height is 170 cm. His BMI will be 25. His total calorie requirement by above guideline will be 2100 Calories per day (at the rate of 30 Calories per kg per day). 210 Calories are deducted as age adjustment (10% reduction per decade). The total requirement comes to 1890 or 1900 Calories. Since Mr IM Healthy is sedentary for all practical purpose, his fat requirement will be 15% of total energy requirement, which comes to 285 calories. One gram of fat yields 9 Calories. Therefore 285 is divided by 9 which comes to 31.6 or 31 gm of fats. 50% of fats is derived from diet as invisible fats. This person should consume only 15-16 gm or three teaspoonful of fats/oils per day. 10% or 1.5 gm should be saturated fats (butter, vanaspati ghee, pure ghee), 8% or less than half teaspoonful should be PUFA (sunflower, safflower, cotton, rice bran oil) and rest two teaspoons should come from mustard, groundnut, soyabean or olive oil.
In cereal based diets, it is necessary to increase the ALA intake and reduce LA from cooking oils. The quality of fats in diet can be improved by using combination of oils. One may use oils with moderate LA/N-6 (groundnut oils, rice bran or sesame oils) or an oil with high LA (safflower, sunflower, cottonseed or corn) with an oil with low levels of LA (palm oil) or use any above oils with ALA/N-3 containing oil (mustard, soyabean). Combination of two oils eg safflower or sunflower (high LA) with palm oils (low LA), or mustard oil or soybean oil (high ALA) with any cooking oil is desired. It does not mean that oils should be blended and used. It means that a variety of oils should be used to get maximum benefits. One dish can be prepared in one oil and other dish in another oil. When variety of oils are used, certain micro components are also obtained. The micro components like tocotrienes in palm oil, ligans in sesame oil, oryzanol and tocotrienes in rice bran oil, reduce blood cholesterol.
To enhance ALA or N-3 fatty acids in diet, regular consumption of plant foods rich in ALA should be done. Cereals (Wheat & Bajra), Pulses and legumes (Black gram/urd dal, cowpea/lobia, rajmah & soyabean), green leafy vegetables (GLV), fenugreek seeds/methi, mustard/rai seeds, mustard and soyabean oils are rich in ALA and must be consumed regularly. Non vegetarians can eat fish 100-200 gm at least twice a week to increase in ALA content. In Eskimos, lower incidence of heart diseases, in spite of high saturated fat intake, is due to high intake of fish products. Consumption of fish is beneficial in heart diseases, diabetes and joint diseases. It also helps in reducing cholesterol, triglycerides, blood pressure and prevents clot formation. It is intimated that clot formation is main cause of angina and heart attacks (myocardial infarction). Fish oils also helps in reducing pain & inflammation of joints in diseases like osteoarthritis and rheumatoid arthritis. Diabetics should not consume fish oils and take fish in natural form. There is an erroneous impression that refined oil is superior. Refining of oils does not improve quality of fatty acids, only appearance is altered.
Foods Rich In N-3 Fatty Acids
In the post I had informed you about various aspects of intake of fats and oils in the diet. These guidelines are applicable to typical Indian diet which is primarily cereal based. However, the principles can be applied to other types of diets in different countries as well. Certain common misconceptions have been explained. The lesson is clear. Limit fat intake. Restrict fried foods. Take fat from variety of sources. Eat foods rich in ALA. PUFA cannot be taken freely in any amount. For day-to-day purpose, I don’t want you to measure each gram of fat consumed, but overall intake be definitely monitored. One should be careful about the total quality and quantity. Fats are not harmful. But there is a limit to every thing. In higher doses even a medicine becomes a poison. Consume fats judiciously. A good knowledge will help you to control heart diseases and diabetes and help you to live longer and healthy.
Those interested must read the booklets ‘Diet and Heart Diseases’ and ‘Diet and Diabetes’ published by National Institute of Nutrition Hyderabad-500007, India
Fats are important for health; Be judicious in consumption
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