Do I Really have to Avoid Fats in Diet?

Nithya, D.J., M. Loganathan, and K. Alagusundaram

THERE is a common belief that eating low fat will result in a better health. It is not always true. Dieticians also talk at bad fat and good fat leading to unending confusions. We should therefore seek answers to these entire popular confusions and understand the facts about the fats in our diet.
Fats do lots of wonders to our health. Following list summarizes the benefits of fat in human body.

  • Insulation: The layer of fat under the skin serves as insulation for the body. Thinner fat layers pose great difficulties to maintaining normal body temperatures.
  • Vital Organ Protection: Layers of fat enclose vital organs like heart, lungs, liver and kidneys to insulate and protect them from injury. When these fat layers are severely depleted, the organs can actually shift from their positions and their functions can be permanently impaired.
  • Energy for Basal Metabolism: Fat keeps the body’s lean tissue (muscle) from being depleted and allows stored glucose to be used as energy for the brain and nerves. The body requires energy for activity and basal metabolism (basic work of the body’s cell).
  • Glucose Metabolism: Fat and protein are metabolized to form glucose like substances for supplying energy to the brain and nerves.
    Fat is a concentrated source of energy. Each gram of fat contains roughly 9 kcal, whereas each gram of carbohydrate and protein contain only 4 kcal. Fat functions as a basic component of every cell in our body and that is the reason why mammals, including humans, produce cholesterol. It is the body’s way of insuring an ample supply of cholesterol for proper cell membrane function.
    Types of fats
    Apart from visible fats (cooking oils, butter and vanaspati are some examples) some amount of fats are present in food items like cereals, pulses, milk, eggs, meat as invisible fat. The fats and oils found in the foods we eat are almost a mixture of saturated, monosaturated and polysaturated fatty acids.

Saturated fatty acids

Saturated fatty acids have the entire hydrogen and the carbon atoms that they can hold. Saturated fats are usually solid at room temperature, and they are stable and do not combine readily with oxygen.

Trans fats are unsaturated, but they can raise total and Low Density Lipoproteins (LDL) cholesterol and lower High Density Lipoprotein (HDL) cholesterol popularly called as bad and good cholesterol, respectively. Trans fats result from adding hydrogen to vegetable oils. French fries, donuts and other commercial fried foods are major sources of trans fat in the diet. Saturated fats and trans fats are the main dietary factors in raising blood cholesterol. The main sources of saturated fats are animal based foods like butter and some plants like palm oil and coconut oil.

During processing, fats may undergo a chemical process called hydrogenation. “Hydrogenate” means to add hydrogen or, in the case of fatty acids, to saturate. The process changes the liquid oil, naturally high in unsaturated fatty acids, to a more solid and more saturated form. Greater degree of hydrogenation results in greater saturation. Recent studies suggest that these fats may raise blood cholesterol. Liquid fat and margarines contain little saturated fat or trans fat.

Polyunsaturated and Monounsaturated Fatty Acids (PUFA and MUFA)

Polyunsaturated and monounsaturated fatty acids are two types of unsaturated fatty acids. Unsaturated fats have at least one unsaturated bond, meaning at least in one place the hydrogen atom is free. They are often found in liquid oils of vegetable origin.

  • Polyunsaturated oils are liquid at room temperature and in refrigerator. They easily combine with oxygen in the air and become rancid.
  • Monounsaturated oils are liquid at room temperature but start to solidify at refrigerated temperatures.

Polyunsaturated fats tend to help your body to get rid of newly formed cholesterol. Thus, they keep the blood cholesterol level down and reduce cholesterol deposits in artery walls. These may also help to reduce the blood cholesterol as long as the diet is with low saturated fat.

Essential Fatty Acids (EFA)

Some fats are however really essential. The body needs Essential Fatty Acids (EFA) just like it needs essential vitamins and minerals to help preventing and treating diseases. They are linoleic and linolenic acid (Short chain poly unsaturated fatty acid) and eicosapentaenoic, docosahexaenoic, gamma linolenic acid, dihomo-gamma-linolenic acid and arachidonic acid (long chain poly unsaturated fatty acid). Some food sources for EFA are fish and shellfish, flaxseed, soya oil, canola (rapeseed) oil, pumpkin seeds, sunflower seeds, leafy vegetables, and walnuts. The EFA also are required by the body to control a large number of cellular processes and also for the development and functioning of the brain and retina.

Omega-3 (n-3) fatty acids are an essential class of PUFAs derived primarily from fish oil. Important nutritionally essential n-3 fatty acids are: á-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). People with certain blood circulatory problems, such as varicose veins, get benefits from fish oils. Fish oils stimulate , increase the breakdown of fibrin, a compound involved in clot and scar formation, and additionally has been shown to reduce blood pressure. There is strong scientific evidence that n-3 fatty acids significantly reduce blood triglyceride levels and regular intake reduces the risk of secondary and primary heart attack.

Sources and Requirements

The daily requirement of visible fat intake is between 20 to 50 g depending on body physical activity and physiological status.

National Cholesterol Education programme released in May 2001, recommends 25 to 35 per cent of one’s daily calorie intake should be from fat. High proportions of saturated fats, with high blood cholesterol levels are mainly found in animal fat (whole milk, cheese, butter, ice
cream and cream) and some plant oil (cocoa and palm oil). The predominant PUFA, an EFA, are commonly found in vegetable seed oils (sunflower oils) and fish oils.

Flax is richest source of omega-3 while cold-water fish (salmon, sardines, mackerel, and herring) are a good source of the metabolites EPA and DHA. Algae oil has both DHA and EPA, suitable for vegans and vegetarians. Fish obtain their DHA and EPA ultimately from the consumption of algae.

A tablespoon of flax seed has about 7.5 gm of the short chain omega-3 which would be converted by the body to about 750 mg of the long chained EPA and DHA. A tablespoon of fish oil, on the other hand, has about 12,000 mg of EPA and DHA. Since the informal NIH recommendations are 660 mg of the long chained omega-3s, the recommended daily intake would be the equivalent of about: 1 tablespoon of flax oil= 3 tablespoons of flax seed = 3 tablespoons of hemp oil = 4 tablespoons of canola oil = 1/4 teaspoon of fish oil.

Saturated fat intake should not exceed 7 per cent of total calories for each day. Trans fat intake should not exceed 1 per cent of total calories for each day. Total fat intake (saturated, trans, monounsaturated, polyunsaturated) should be adjusted to fit total caloric needs.  Obese people should consume not more than 30 percent of total calories from fat.

Before reducing your fat intake please remember that fat is not the sole factor for health complications. What matters is how much of the cholesterol the person eats? It is important to balance the intake of energy with our overall energy expenditure to avoid unintentional or excessive weight gain. Consuming more calories than our body needs, whether fats, carbohydrates or protein will lead to health complications. Therefore, a low fat diet not combined with overall calorie control or energy balance can also lead to excessive weight gain.

Fats That Raise Cholesterol Examples
Dietary Foods from Meats, egg yolks, dairy
cholesterol animals

products, organ meats (heart, etc.), fish and poultry

Saturated fats Foods from Whole milk, cream, ice
  animals cream, whole-milk cheeses, butter, lard and meats
  Plant oils Palm, palm kernel, coconut
Trans fats Partially oils, cocoa butterCookies,
  hydrogenated crackers, cakes, French
  vegetable fries, fried onion rings, do
  oils nuts
Fats That Lower Cholesterol

Examples

Polyunsaturated Plant oils Safflower, sesame, soy,
fats  

corn and sunflower-seed oils, nuts and seeds

Monounsaturated Plant oils Olive, canola, peanut oils,
fats   avocados

 

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