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Functions of lipids (fats)

Nutritional requirements

Classification of lipids (fats)

Trans fats

Essential Fatty Acids (EFA), Omega-3 and Omega-6


   Lipids (fats) belong to a big group of natural organic compounds, insoluble in water but soluble in organic dissolvents such as: diethyl ether, petroleum benzine, chloroform, benzene, acetone etc. To lipids (fats) also belong derivatives of natural lipids and related with them compounds which retain properties of lipids. Lipids (fats) occur in all live organisms. In plants they are present first of all in seeds and flesh of fruit, and in animal organisms in different organs or as separated adipose tissue.

Functions of lipids (fats)

  • lipids (fats) are the most concentrated source of energy: from 1 g of fats 9 kcal are released,

  • lipids (fats) are convenient and main source of spare material (they allow to take breaks between meals, during work they enable organism to function beyond thermal neutrality zone - body temperature keeping), 

  • accumulated in tissue fats protect against excessive heat emission, enables to adopt at low temperature, inside organism keeps organs in constant location and prevents their dislocation,

  • accumulated in organism lipids are a warehouse of water, 30-50% of adipose tissue makes up water, combustion of 100 g of adipose tissue releases 107 g of water,

  • mixed lipids (fats) of nourishment are a source of vitamins soluble in fats: A, D, E, K, and Essential Fatty Acids (vitamin F),

  • fats in food save the balance of proteins of vitamins from group B,

  • they have high satiating value - they inhibit gastric juice secretion, raise flavor of dishes,

  • they fulfill function of building material, are ingredient of cell membranes and constitute element of composition of many hormones, cholesterol and important intracellular substances.

Nutritional requirements

   Fats should provide 20-35% of energetic value of a daily nutritious ration for an adult. They ought to be fats unsaturated, not chemically hydrogenated, devoid of trans isomers. 

RDA for various life stage groups - Total fat. Fat has no RDA and we have only percentage range of AMDR.

Life stage group Total fat
Recommended Dietary Allowances (RDA)
Acceptable Macronutrient Distribution Range (AMDR)*1
Infants 0-6 months 31 -
Infants 6-12 months 30 -
Children 1-3 years -
Children 4-8 years -
Males 9-13 years -
Males 14-18 years -
Males 19-30 years -
Males 31-50 years -
Males 51-70 years -
Males > 70 years -
Females 9-13 years -
Females 14-18 years -
Females 19-30 years -
Females 31-50 years -
Females 51-70 years -
Females > 70 years -
Pregnancy ? 18 years -
Pregnancy 19-30 years -
Pregnancy 31-50 years -
Lactation ? 18 years -
Lactation 19-30 years -
Lactation 31-50 years -

*1  Acceptable Macronutrient Distribution Range (AMDR) is the range of intake for a particular energy source that is associated with reduced risk of chronic disease while providing intakes of essential nutrients. If an individuals consumed in excess of the AMDR, there is a potential of increasing the risk of chronic diseases and insufficient intakes of essential nutrients.

Classification of lipids (fats)

   In terms of chemical build lipids can be divided into:

Simple lipids - esters of fatty acids and alcohols.

Compound lipids - compounds contains apart from fatty acids and alcohols, other constituents as well.

Derived lipids - derivatives of simple lipids and compound lipids. Obtained from hydrolysis of fats, usually contains an even number of carbon atoms and are straight chain derivatives.

  • Fatty acids

  • Fatty alcohols

  • Hydrocarbons

  • Fatty aldehydes

  • Vitamins A, D, E, K


Neutral fats
They are esters of fatty acids and glycerol.

They are esters of higher fatty acids and alcohols other than glycerol.

They are lipids containing phosphoric acid as monoester or diester.

They are compounds containing at least one sugar connected by glycosidal bond with lipid part.

Fatty acids
Fats are built of fatty acids, which chemical build determines division of these compounds into saturated, monounsaturated (monoenous) and polyunsaturated (polyenous) fatty acids.

Saturated fatty acids (more important):

  • butyric

  • caproic

  • caprylic

  • capric

  • lauric

  • myristic

  • palmitic

  • stearic

  • arachidic

Monounsaturated fatty acids (more important):

  • myristoleic

  • palmitoleic

  • oleic

  • eicosenic

  • erucic

  • cetoleic

Polyunsaturated fatty acids - (Omega-3 and Omega-6) (more important):

  • linoleic (LA) (Omega-6)

  • gamma-linolenic (GLA) (Omega-6)

  • arachidonic (AA) (Omega-6)

  • alpha-linolenic (LNA or ALA) (Omega-3)

  • eicosapentaenoic (EPA) (Omega-3)

  • docosahexaenoic (DHA) (Omega-3)

Trans fats

   Natural liquid vegetable oils are comprise mainly of unsaturated fatty acids. Trans fats are formed when manufacturers turn liquid oils into solid fats. Trans isomers has the same chemical formula as normal isomers (Cis isomers) except for the fact that its hydrogen atom is in a different spatial arrangement. During the hydrogenation of vegetable oil - a commercial process to harden oil for production of fats like shortening and hard margarine. As a result of this process, oils become semisolid, more stable at room temperature and more saturated. Trans isomers melt at 44oC (111oF). Cis (normal) isomers melt at 13oC (55oF). Hydrogenation increases the shelf life and flavor stability of foods. Trans fats can be found in a list of foods including vegetable shortening, margarine, crackers, cereals, candies, donuts (doughnuts), baked goods, cookies, granola bars, french fries (chips), snack foods, salad dressings, fats, fried foods, and many other processed foods. Trans fats are found naturally in small quantities in some foods including beef, pork, lamb, butter and milk. Typical french fries have about 40% trans fats and many popular cookies and crackers range from 30-55% trans fats, donuts have about 35-40% trans fats. Trans fats are known to increase blood levels of low density lipoproteins (LDL), or "bad" cholesterol, while lowering levels of high density lipoproteins (HDL), known as "good" cholesterol. It can also cause major clogging of arteries, type 2 diabetes and other serious health problems and was found to increase the risk of heart disease.

Essential Fatty Acids (EFA), Omega-3 and Omega-6

   Fatty acids are simply components of fats. There are two essential fatty acids. Essential means we need to get them from the diet because the body can't produce them. The first is alpha-linolenic (LNA or ALA, omega-3), and it belongs to the omega-3 parent. We can find alpha-linolenic in flax seed and flax oils, rape seed and rape oils, walnuts, hemp oil, cold pressed canola oil, wheat germ, dark green leafy vegetables. Linoleic acid (LA, omega-6) is the other essential, belonging to the omega-6 parent. We can found it in soy oil, sunflower seeds, safflower seeds, pumpkin seeds, sesame seeds, corn oil, and in most nuts. There exist also other (non-essential) omega-3 and omega-6 fatty acids, which our body can produce from the two essential ones. Non-essential omega-3 fatty acids include: docosahexaenoic (DHA, omega-3) and eicosapentaenoic (EPA, omega-3), which the body makes from alpha-linolenic (LNA or ALA, omega-3). They are contained first of all in food of sea origin (in fish i.e. mackerel, salmon, tuna, halibut, cod, herring, sardine, pilchard), linseed and rapeseed oils. Infants and children need DHA for proper brain growth from their diet (and breast milk can have DHA), so in that sense we should classify DHA as an essential fat for children. Non-essential omega-6 fatty acids include: gamma-linolenic and arachidonic which our body makes from linoleic acid (LA, omega-6). Fish oils contain the non-essential omega-3 fatty acids EPA and DHA. Since the body can make them from LNA, it follows that it isn't absolutely necessary to eat fish or take fish oil supplements but in all cases it is necessary to get LNA. However, in certain cases the conversion from LNA to EPA or DHA is not adequate. That can happen if we don't get enough of the raw material LNA, or if we don't get enough of vitamins: niacin, B6, C or enough zinc and magnesium, which all are needed in the conversion from LNA to DHA and EPA. Also, if the diet contains too much omega-6 fats in comparison to LNA, then the conversion is slowed down, so increasing dietary intake of fish in this case is highly desirable. The highest value and biological activity possess omega-3. The appropriate ratio of omega-6 to omega-3 should be (<5:1). The ratio of omega-6 to omega-3 (<5:1) has been based on the simple logic that this approximates that ratio in our cell membranes and also from evidence regarding food habits of Paleolithic people. Light, air and heat destroy EFA, so should be kept away from light, heat and air.


Role of EFAs:

  • they make up one of essential building materials of cells, maintain stability in cell division by protecting chromosomes,

  • they take part in metabolism of cholesterol and its transport (over a half of cholesterol esters occurs in form of joint with linoleic acid what makes easier their distribution in organism, they decrease cholesterol level in blood),

  • they inhibit aggregation of thrombocytes, cause expansion of blood cells including coronary ones, act anti-arrhythmically,

  • they are precursors to biosynthesis of prostaglandins and prostacyclines,

  • omega-3 seems to help regulate the body's blood sugar levels, which helps keep hunger at bay. In the long term, it is believed that a diet rich in omega-3 might lower the risk of diabetes and obesity,

  • a new study of teenagers has found that consumption relates to lower hostility rates in teenagers. Hostility has been shown to predict the development and manifestation of heart disease,

  • they participate in transportation of water and electrolytes through biological membranes,

  • they regulate expelling of sodium ions from organism,

  • facilitate the conversion of lactic acid to water to carbon dioxide thereby speeding up muscular fatigue recovery,

  • assist in hemoglobin production,

  • mediating the release of inflammatory substances from cells that may trigger allergic conditions,

  • inhibit tumor growth.


Deficiency of EFAs causes:

  • inhibition of growth and decrease of mass increment,

  • dermal changes and hair losing,

  • liver and kidney degeneration,

  • male sterility and female miscarriages,

  • increased sensitiveness on allergic changes and bacterial infections,

  • drop of cardial muscle tension (lower systole power, worse blood circulation, swellings).

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