Diabetes Nutrition - Fats
Fat is a compact source of energy. One gram fat supplies 9 kcals, more than double the calorie value of carbohydrates and proteins. Fat stored in the body is an important long-term reserve of body fuel. It is a major constituent of cell walls. Fats provide two essential nutrients, essential fatty acids and fat soluble vitamins. Fat is a Taw material for many hormones. Fat makes the food palatable and slows the emptying time of stomach.
Fat may be visible as in butter, ghee, oil (groundnut, mustard, coconut, safflower, til) and hydrogenated vegetable oil or vanaspati. Invisible fat is present in nuts, oilseeds, soyabean, animal foods and even in cereals and pulses.
According to the source, fats can be grouped as follows:
Vegetable fats/oils: Groundnut, mustard, safflower, sunflower, corn, coconut, palm etc and hydrogenated vegetable oil {vanaspati).
Animal fats: Butter and ghee.
Fish oils: Shark and cod liver oils. EPA, the chief fatty acid of the fish oils, inhibits clumping of platelets and the process of blood clotting.
A fat is made of glycerol and fatty acids. Fatty acids differ in their length and may be saturated (without a double bond), mono-unsaturated MUFA (with one double bond) or polyunsaturated PUFA (with more than one double bond). A fat is called saturated or unsaturated according to its predominant fatty acid.
Saturated fats are usually solid at room temperature and are found predominantly in ghee, most dairy products, meat, coconut and palm oil and some types of margarine and vanaspati.
Polyunsaturated fats arc usually liquid at room temperature. Examples are sunflower, safflower, soya oil and fish oil.
Monounsaturated fats are usually liquid at room temperature and occur in vegetable oils like groundnut, rape seed and olive. Foods high in monounsaturated fatty acids include meat, poultry, sardines, groundnuts and almonds.
Animal fats contain vitamin A and D. Vegetable oils provide vitamin E. Vanaspati is fortified with vitamin A and D. Vegetable oils provide essential fatty acids, linoleic (n-6) alpha-linolenic (n-3), deficiency of which gives rise to rough skin.
Dietary cholesterol comes from animal foods like ghee, butter, cheese, milk, curd, egg yolk, flesh foods, meats, fish and prawns. Cholesterol is absent in plants and hence in vegetable oils. Cholesterol is an important constituent of animal cell membranes. It is synthesized in the body and therefore is not an essential constituent of diet.
Fats in the blood are called lipids. Cholesterol and triglycerides are important blood lipids. Lipids are insoluble in blood and hence are transported in blood as lipid and protein complexes, called lipoproteins. The lipoproteins are classified according to their density. Very low density lipoproteins (VLDL) are carriers of cholesterol and triglycerides synthesized in the body. They reflect synthesis of lipids in the body. Low density lipoproteins (LDL) carry cholesterol from the liver to the tissues for example arteries. Tin's is the larger fraction of total cholesterol in blood. The high density lipoproteins (HDL) carry the cholesterol from the tissues other than liver (for example arteries) to liver. This is smaller fraction of total cholesterol and is called 'good' cholesterol.
If the blood lipids are increased, they are deposited in the lining of arteries, first as streaks and later as plaques. The material in the plaque resembles porridge, hence the term atheroma. The artery becomes hard later on (sclerotic), hence the term "atherosclerosis" for this disease of arteries. Stickiness of blood and formation of a clot of blood are important aspects of this diease.
High intake of saturated fatty acids increases the levels in the blood of total and LDL cholesterol and accelerates atherosclerosis and formation of blood clot (thrombosis). Saturated fatty acids increase blood pressure. PUFA, on the contrary, have opposite effect.
All common vegetable oils except coconut and palm oil are predominantly unsaturated. Invisible fat present in nuts, oilseeds, cereals, pulses, legumes, roots and tubers, vegetables, spices and fruits is predominantly unsaturated. Linoleic acid is the predominant (n-6) PUFA, in most plant foods and vegetable oils. Mustard, soyabean oils, blackgram, cowpea, pulses, fenugreek (methi) and mustard seeds, green leafy vegetables, wheat and bajra are good sources of alpha linolenic acid (n-3) (PUFA), which is less active than EPA of the fish oils.
Total amount of fat should not exceed 80 g/day, that is 30 per cent of total Kcals. Even a cereal-pulses based Indian diet provides 15 g fat, half of which is essential fatty acids. In addition to this, 15-25 g of visible fat in the form of groundnut oil should supply the essential fatty acids. Consumption of small amount of fat, a number of times, results in less rise in blood cholesterol level as compared with consumption of same amount of fat, at one time of the day. The blood cholesterol raising action of saturated fats increases with an increase in cholesterol intake. The cholesterol intake, hence should be kept as low as possible