Fatty acids


Fatty acids (basic units of the lipid class) consist of a carbon chain (bonded carbon atoms on which hydrogen and oxygen atoms are attached). The carbon chain of fatty acids can contain up to 30 carbon atoms. It generally has a number of carbon atoms ranging from 14 to 22.


There are three categories of fatty acids: saturated fatty acids (SFA), which are solid at room temperature; mono-unsaturated fatty acids (MUFA), which are liquid at room temperature but tend to solidify at lower temperatures (e.g., freezer) and whose carbon chain contains one double bond; and polyunsaturated fatty acids (PUFA), which contain multiple double bonds and remain liquid even in the freezer. They are the constituents of triglycerides and phospholipids.


The degree of unsaturation is of great interest because excessive consumption of saturated fats could have negative health implications. For example, it has long been known that a diet rich in saturated fatty acids is associated with high plasma cholesterol levels, while a diet rich in polyunsaturated fatty acids, such as those found in oils obtained from fish, decreases cholesterol levels.


General formula of a fatty acid:


(saturated: m=0; monounsaturated: m=1; polyunsaturated: m>1)  


Essential fatty acids


Essential fatty acids are certain polyunsaturated fatty acids, the presence of which is essential for balanced physiological reactions and thus optimal health; they cannot be synthesized by the body and must necessarily be introduced through the diet.


Mammals are able to synthesize saturated and monounsaturated fatty acids "de novo" from simple precursors such as glucose and amino acids.


These fatty acids, called essential fatty acids, are represented by two subgroups: n-3 and n-6 fatty acids, more commonly known as Omega-3 and Omega-6.


The number 3 or 6 is derived from the position of the last double bond between the carbon atoms: if this is six carbon atoms from the end of the carbonaceous chain, we speak of an Omega 6 fatty acid (omega is the last letter of the Greek alphabet and is often used in scientific language to define an end), while, if the last double bond is only three carbon atoms from the end of the carbonaceous chain, we speak of an Omega 3 fatty acid.




Mono-unsaturated fatty acids (MUFAs)


Fatty acid whose carbon chain contains a double bond (a bond between two carbon atoms that is not "saturated" by hydrogen atoms). This unsaturation makes the chain more flexible with ability to deform more freely in space. These fatty acids are in liquid form at room temperature but tend to solidify in the freezer.


This is the case with olive oil whose main constituent is the monounsaturated fatty acid oleic acid.


Omega-3 fatty acids


Omega-3 fatty acids represent a family of essential fatty acids (see this definition) particularly abundant in fish oils that exert a significant influence on the structure of cell membranes and the balance of physiological reactions in the body.


They give cell membranes a special fluidity that is indispensable to transmembrane exchanges with the interior of the cell and to intercellular communication.


Omega-3s have antiaggregatory properties on platelets and control, in part, inflammatory reactions by preventing them from becoming excessive, while at the same time aiding in the fight against external attacks on the body.


The main omega-3 fatty acids are as follows:


Alpha-linolenic acid (ALA)


It is the synthetic precursor of long-chain Omega-3. It is a plant-derived Omega-3 fatty acid and is mainly found in some algae, some green legumes and some seeds e.g., flax seeds. Within the body, ALA is converted to EPA and DHA, the long-chain fatty acids that are biologically active in mammals. In humans this conversion capacity is reduced.


The carbon chain of ALA contains 18 carbon atoms and 3 double bonds and for simplification can be denoted as C18:3n-3 where the number immediately following the C indicates the number of carbon atoms in the essential fatty acid, while the number following the colon indicates how many double bonds are in the molecule.


Eicosapentaenoic acid (EPA)


After ingestion, ALA is partially transformed into EPA, which has more direct effects on the physiology of the human body.


EPA is a precursor to a class of molecules (the 3-series eicosanoids) involved in fighting infection and cancer cells and controlling AA-derived eicosanoid-mediated inflammatory reactions and cytokines. EPA can be partially converted to DHA acid when sufficient EPA is available.


The carbon chain of EPA contains 20 carbon atoms and 5 double bonds (C20:5n-3).


Human studies have shown that the efficiency of EPA synthesis from ALA is very low: only 5-10% of ALA is converted to EPA. Therefore, if you aim to get the maximum benefits of EPA, you would be better off taking pre-formed EPA from animal sources, rather than ALA-rich plant sources such as flaxseed.


DHA is the structural fat for the brain, while EPA is critical for health. Fish oil contains both in abundance.




Docosahexaenoic acid (DHA)


Through a series of enzymatic reactions, starting with EPA, the body synthesizes DHA, the omega-3 fatty acid found predominantly in the lipid composition of cell membranes, especially in the lipids of the brain, sperm and retina. The presence in adequate amounts of DHA in breast milk is believed to be of paramount importance for optimal development of the baby's brain.


DHA can also be converted back to EPA by the same enzymes primarily used to produce DHA. The latter process is very difficult and inefficient and is one reason why dietary supplementation of DHA alone (without EPA) does not have as pronounced an effect on the control of inflammatory reactions or emotional balance as supplementation of EPA alone. While DHA is predominantly involved in cell structure, EPA has a more direct and more targeted action on the balance of physiological reactions.


The carbon chain of DHA contains 22 carbon atoms and 6 double bonds (C22:6n-3)


Omega-6 fatty acids


Omega-6 fatty acids represent a family of essential fatty acids (see definition) that are essential to the structure of cell membranes and affect the balance of physiological reactions in the body.


Omega-6 fatty acids are the precursors of certain molecules that promote inflammatory reactions (the pro-inflammatory eicosanoids). These molecules are very important for the normal and regular functioning of the body. In particular, when Omega-6 fatty acids are not balanced by a sufficient presence of Omega-3 fatty acids (especially by the stabilizing influence of EPA), they induce excessive inflammatory reactions that may manifest with particular symptoms (as in the case of arthritis) or even give rise to certain so-called "autoimmune" diseases during which the immune system turns against its own body by producing antibodies against normal tissues.


The balance between Omega-6 and Omega-3 is the main factor that determines the physical and mental health of the human body.


The main omega-6 fatty acids are as follows:


Linoleic Acid (LA)


It is the synthetic precursor of long-chain omega-6 fatty acids. It is the main constituent of most vegetable oils (except olive oil, linseed oil, and canola oil). LA is especially abundant in corn (a major nutritional source for livestock).


The carbon chain of LA contains 18 carbon atoms and 2 double bonds (C18:2).


Gamma-linolenic acid (GLA)


In the body, LA is transformed through an enzymatic reaction into GLA.


GLA is an isomer of the more common ALA. GLA comes from many plant sources (e.g., blackcurrant) and is available as a dietary supplement in oil form, e.g., primrose or borage oil.


The carbon chain of GLA contains 18 carbon atoms and 3 double bonds (C18:3).


Experimental evidence shows that intake of this acid is beneficial for therapeutic and nutritional purposes.


Arachidonic Acid (AA)


AA is the most abundant essential fatty acid in our bodies. It is chemically produced from dietary sources of LA and GLA. It is present in high concentrations in animal phospholipids and, for commercial purposes, is generally isolated from liver lipids. It is also present in some ferns and may be produced by fermentation of particular microorganisms. It plays a key role in the structure of cell membranes particularly in those of neurons in the brain.


The carbon chain of arachidonic acid contains 20 carbon atoms and 4 double bonds. It is the precursor of a class of compounds called series 2 eicosanoids. Biologically active eicosanoids derived from arachidonic acid include prostaglandins, thromboxanes, and leukotrienes. Eicosanoids exert specific physiological effects on target cells near the site where they are synthesized and are catabolized extremely rapidly: these compounds are considered short-lived, locally acting hormones (autocrine hormones). Eicosanoid metabolism represents an extremely important therapeutic target for drugs used to control inflammatory processes (aspirin) blood coagulation and gastric secretion and to manipulate reproductive processes in various ways.


Polyunsaturated fatty acids (PUFAs)

Polyunsaturated fatty acids are composed of a carbon chain that contains many double bonds or unsaturations (many carbon-carbon bonds are not "saturated" by hydrogen atoms). This polyunsaturation causes the chain to be very flexible and such that it allows optimal function of the membranes of the cells of which it is a part. These fatty acids are liquid even at low temperatures. 


Saturated fatty acids (SFA)


Saturated fatty acids consist of long saturated carbon chains. Carbon chains are said to be "saturated" when all carbon-carbon bonds are simple, that is, "saturated" by a certain number of hydrogen atoms.


These chains have a rigid structure, which is why fats such as butter and other fats of animal origin, are solid at room temperature. These saturated fatty acids give the body's cell membranes a rigid structure that does not facilitate the communication and intercellular exchanges that are essential for the proper maintenance of physiological balance.



Cholesterol is a member of the lipid family. It is a fat-like substance found in blood, muscle, liver, brain and other human tissues. It becomes part of the structure of many animal membranes on whose fluidity it has a specific and complex effect and is the synthetic precursor of very important hormones such as the sex hormones of higher animals, adrenaline and cortisol. It is produced in the body, particularly in the liver, and also comes from food (meat, dairy products, seafood and fish). A balanced amount of cholesterol is necessary for maintaining good health while an excess may be harmful.




Dioxins are chemical compounds consisting of four carbon atoms and two oxygen atoms and containing two double bonds in the ring they form. The name is misused to refer to the highly toxic TCDD (its toxicity to give an example is much higher than cyanide and strychnine). In sublethal amounts it causes a disfiguring skin disease called chloroacne. 


Dioxins are molecules that degrade very slowly. It persists for a long time in the environment, and because of its solubility in fats, it propagates through the food chain.


Dioxins are industrial pollutant byproducts that readily bioaccumulate in the fatty tissues of fish. Studies in animal species show how continuous exposure to them (e.g., consuming contaminated fish, regularly and for extended periods) can cause neurological damage, significant alterations in the immune system, and increased incidence of abortions.


Dioxin has been found to be teratogenic (capable of causing fetal malformations) in small animals and probably, though less frequently, in women. It has been classified as a probable carcinogen (increased incidence of liver and lung cancer has been observed in the laboratory).


As with mercury, dioxins are most risky for pregnant women and children.


In July 1976 an 'explosion at a chemical plant in Seveso, Italy, caused the release of an estimated 22 to 132 tons of dioxin into the atmosphere. The plant was used to produce a compound (itself used for the production of a herbicide) but the reaction temperature went out of control resulting in the release of the dioxin cloud.


The result was that a great many animals died and many people were affected by dermatitis.


A study conducted 25 years after the Seveso accident on 48 people from contaminated areas showed that the normal development of children's teeth is one of the most sensitive targets for dioxin toxicity.


Another study, some 20 years after Seveso, showed how TCDD inhibits antibody production; this results in decreased resistance to bacterial, viral and parasitic infections. The immune system is thus another target that is highly susceptible to the harmful dioxin-induced effects.




They are a complex and numerous family of molecules consisting of 20 carbon atoms (éikosi means 20 in Greek) derived from polyunsaturated fatty acids of which arachidonic acid is the main one. These molecules behave as intercellular mediators and/or as locally acting hormones and are of great physiological and pathophysiological importance especially relative to the control of inflammatory processes.


Good and bad eicosanoids The most studied eicosanoids are undoubtedly the prostaglandins. There are more than 30 types, divided into 3 families: the PG1 and PG2 families are derived from omega-6 fats (the progenitor of which is linoleic acid), the PG3 family from omega-3 fats (the progenitor of which is linolenic acid). The prostaglandins with the greatest health effects are PG1 and PG2.


The former (especially PGE1) perform the following functions:


  • They lower blood pressure by promoting sodium removal and fighting water retention;
  • prevent platelet aggregation, preventing the occurrence of thrombi and heart attacks;
  • They inhibit the inflammatory response;
  • improve insulin function and keeps blood sugar steady;
  • They regulate calcium metabolism;
  • They improve the functioning of the nervous system;
  • They improve the functioning of the immune system.


PG2 prostaglandins can be good or bad. PGE2 causes water retention, platelet aggregation, inflammation, and increased blood pressure. PGI2, on the other hand, is good because it acts similarly to PGE1.


When man was a hunter, surely eicosanoids like PGE2 could save him in difficult situations (to heal from wounds, for example). In the age of affluence and sedentariness, it can come to be an enemy substance.




It is a chemical compound that is obtained from the reaction between an alcohol and an organic or inorganic acid by means of a bond that is covalent in nature. The nomenclature of esters is derived from acids with the ending -ato ( e.g., ethyl acetate). Esters usually have a pleasant odor often reminiscent of fruit, so much so that these compounds are widely used in the production of synthetic flavorings.


Ethyl esters and glyceryl esters differ in alcohol composition, ethanol for some, glycerol for others.



Phospholipids are lipids whose carbon chain contains one or more phosphorus atoms hence the name phospholipids. They are essential constituents of the structure of cell membranes.





Lipids represent a heterogeneous group of compounds that have in common: insolubility in the aqueous environment of the cell; solubility in organic solvents, such as ether, benzol, etc.; specific gravity lower than water; and fairly low melting point. Low solubility makes lipids suitable for one of their most important biological functions: forming the main structural element of the membranes that surround cells and separate them into various compartments.


Lipids are classified into simple lipids, which consist exclusively of carbon, hydrogen and oxygen, and complex lipids, which contain nitrogen, phosphorus and sulfur in addition to carbon, hydrogen and oxygen. Lipids come from food products of animal origin (butter, dairy products, fats, meats) and vegetable origin (oils, margarine, nuts, olives).


The lipid family includes among others: triglycerides (simple lipids) and phospholipids (complex lipids).






Mercury a chemical element of symbol Hg. It is found free in nature in droplets adhering to cinnabar, in amalgam form, and in the mineral cinnabar, which is the most important. It is a shining silver-gray, extremely ductile, liquid metal at room temperature. It is used in the preparation of detonating products, antiseptics, to extract gold and silver, in the manufacture of physics apparatus (thermometers, barometers, etc.), for mercury vapor lamps.


Mercury and its derivatives are toxic. It is the main pollutant found in fish-in fact, most fish and shellfish contain trace amounts of mercury.


Organic mercury compounds pass through the food chain and accumulate in humans. In water, mercury is converted to methyl mercury, a potent neurotoxin that destroys nerve tissue. When humans eat fish, methyl mercury accumulates in the bloodstream. Recent findings indicate that mercury is linked to cholesterol oxidation and may increase the risk of a heart attack in at-risk individuals.


Thus, it is understood how the cardiovascular benefits of fish consumption are attenuated in the presence of organic mercury, which indeed accelerates the development of heart disease. In addition, mercury is a metal that accumulates at the tissue level (bioaccumulation) and can pass from the pregnant woman to the fetus going on to contribute to disorders related to the child's learning and memory capacity.


In a study conducted in eight European countries and Israel, levels of mercury in toenails and DHA in adipose tissue were related to the risk of myocardial infarction in men. A total of 684 men who had been first diagnosed with myocardial infarction and 724 men as a control group were considered for this purpose.


The results clearly showed that, unlike the DHA in adipose tissue, the level of mercury in nails is directly related to the risk for humans to experience myocardial infarction. It is evident how a high mercury content can therefore diminish the cardioprotective effect of fish consumption.






Polychlorobenzenes, or PCBs, are a class of organic compounds containing anywhere from 1 to 10 chlorine atoms that bind to two attached benzenes. Benzene is an aromatic hydrocarbon of formula C6H6, with a ring structure (benzene ring) having the 6 carbon and hydrogen atoms each placed at the apex of a regular hexagon, linked alternately by a simple and a double bond.


The general formula of polychlorobenzenes (PCBs) is C12H10-xClx. These compounds are actually mixtures of variously chlorinated dibenzenes classified precisely on the basis of their chlorine content, which usually varies between 40 and 60 percent. As many as 210 variously chlorinated dibenzenes can theoretically be prepared, but a typical commercial mixture (usually a clear viscous liquid) contains about fifty. The uses of PCBs are manifold: heat exchangers in transformers, plasticizers for the production of polystyrene objects, printing inks and carbon paper, additives in pesticides, pei microscope fixing agents, and flame retardants.


Polychlorobenzenes (PCBs) are degraded very slowly (due to their chemical, physical and thermodynamic stability) and being insoluble in water but soluble in fat they tend to gradually accumulate up the food chain. Fish living in PCB-contaminated waters have PCB levels 100 to 100,000 times higher than in the water itself, and this ratio is even higher in birds that feed on such fish.


Fish collect and concentrate algae-derived fatty acids (long-chain omega-3 EPA and DHA) but also other fat-soluble toxic substances (industrial pollutants) such as organic mercury, PCBs, and dioxins in the adipose tissues. All substances discharged into the sea eventually tend to concentrate in fish.


Experimental evidence shows that persistent exposure to high levels of polychlorobenzenes (PCBs) has adverse health effects due to bioaccumulation problems at the level of animal tissues. Under these conditions, damage has been found especially in the liver and skin barrier but also in the kidneys, stomach and thyroid.


Continued exposure to PCBs has been correlated with the presence of liver and biliary tract cancers showing how these compounds are likely carcinogenic. A group of researchers analyzed the behavior of children born to women who had regularly fed on fish contaminated with polychlorobenzenes (PCBs) from Lake Michigan. Compared with the control group, these children were three times more likely to have lower than average IQs and twice as likely to have difficulties related to learning and reading skills.




In living things, fatty acids are stored mostly in the form of triglycerides i.e., fats. A mammal may contain between 5 and 25 percent, or more, of its body weight; more than 90 percent of these lipids are fats. These substances consist of one molecule of glycerol and three molecules of fatty acids that may be saturated, mono-unsaturated, or poly-unsaturated.


In adipocytes, the animal cells that specialize in accumulating fat deposits, almost the entire cell volume is filled with a single large drop of fat. Such cells make up most of the adipose (fat) tissue of animals. Fat is the main form of energy storage in many organisms. In animals, fat storage serves three specific functions: energy production, heat production, and thermal insulation (in animals living in cold environments, layers of fat cells are present beneath the skin to provide thermal insulation).


Fats are derived from three main sources: diet; ex-novo biosynthesis, especially in the liver; and mobilization of accumulated fat in adipocytes.


Carbohydrates ingested in excess of the possibility of being broken down or stored are readily converted to fat.