Omega-3 fatty acids

Omega-3 fatty acids are polyunsaturated fatty acids found in certain fish tissues, and in vegetable sources such as flax seeds, hemp seeds, walnuts, and canola oil. Omega-3 fatty acids are classed as essential fatty acids. Fatty acids are the major building blocks of fats and important sources of energy in the human body. Essential fatty acids (EFAs) aid the body in many ways. As structural parts of cell membranes and the membranes of subcellular organelles, EFAs are indispensable.

The term omega-3 signifies that the first double bond in the carbon backbone of the fatty acid, counting from the end opposite the acid group, occurs in the third carbon-carbon bond. They are called omega-3 fatty acids because the first double bond counting from the methyl end of the fatty acid is located at the third carbon atom.

There are three major types of omega 3 fatty acids that are ingested in foods and used by the body: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Through an inefficient enzymatic process of desaturation, ALA produces EPA (20 carbons) and DHA (22 carbons), precursors to a group of eicosanoids (prostaglandins, thromboxanes, and leukotrienes) that are anti-inflammatory, antithrombotic, antiarrhythmic, and vasodilatory. The longer chain fatty acid derivative of linoleic acid is arachidonic acid (20 carbons), which is a precursor to a different group of eicosanoids that are proinflammatory and prothrombic.

ALA and linoleic acid use and compete for the same enzymes in the production of their longer chain fatty acids, EPA, and arachidonic acid. The ingestion of fish and fish oil provides EPA and DHA directly, therefore avoiding the competition for enzymes to convert ALA to EPA. Fish and fish oil are rich sources of omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Alpha-linolenic acid (ALA) is an omega-3 fatty acid present in seeds and oils, green leafy vegetables, and nuts and beans (such as walnuts and soybeans).

Omega-3 fatty acid has been recognized as having health benefits, including helping to regulate blood pressure and blood lipid levels. Omega-3 fatty acids are structural components of cell membranes and are particularly concentrated in the brain and the retina. Omega-3 fatty acids lower plasma triglyceride levels, particularly in persons with hypertriglyceridemia, by inhibiting the synthesis of very-low-density lipoprotein (VLDL) cholesterol and triglycerides in the liver. Omega-3 fatty acid intake (primarily from fish), helps protect against stroke caused by plaque buildup and blood clots in the arteries that lead to the brain. People with diabetes tend to have high triglyceride and low HDL levels.

Omega-3 fatty acids such as EPA help increase levels of calcium in the body, deposit calcium in the bones, and improve bone strength. Omega-3 fatty acids appear to have a dose-response hypotensive effect in patients with hypertension and have little to no effect in normotensive patients. EPA and DHA found in fish oil help reduce risk factors for heart disease including high cholesterol and high blood pressure. Omega 3 fatty acids also aid in the prevention of arthritis and improve skin and hair condition.

Omega-3 fatty acids are found in certain fatty fish and vegetables. EPA and DHA are found in cold-water fish such as salmon, mackerel, halibut, sardines, and herring. ALA is found in flaxseeds, flaxseed oil, canola (rapeseed) oil, soybeans, soybean oil, pumpkin seeds, pumpkin seed oil, purslane, perilla seed oil, walnuts, and walnut oil. Larger fatty fish such as tuna also contain omega-3 in somewhat lesser amounts, but should perhaps not be eaten in great quantities due to the potential for heavy metals which accumulate up the food chain. Additionally, with the greater lifespan of larger fish, more toxic heavy metals and other contaminants may accumulate.

Docosahexaenoic acid (DHA) is a highly unsaturated fatty acid that is greatly concentrated in rod photoreceptor cells. This omega-3 fatty acid is a major structural component of brain, nerve and retinal membranes. Docosahexaenoic acid is composed of 22 carbon atoms and six double bonds. Because the first double bond, as counted from the methyl terminus, is at position three, DHA belongs to the so-called omega-3 group. In recent years, DHA has attracted much attention because of its beneficial effect on human health.

DHA has been associated with optimal memory function, visual activity, and maintaining a positive mental state. DHA is transformed to newborn babies through breast milk. This fatty acid plays a unique role in fetus development and is extremely important during the first few months of life. DHA is is the most abundant long chain polyunsaturated fatty acid (PUFA) in the grey matter of the brain. Omega-3-fatty acids in general are known to be beneficial in reducing the incidence of coronary heart disease.

Biological functions in human health

Docosahexaenoic acid (DHA) is essential for the growth and functional development of the brain in infants. DHA is also required for maintenance of normal brain function in adults. DHA can reduce the level of blood triglycerides in humans, which may reduce the risk of heart disease. DHA's triglyceride-lowering property results from the combined effects of inhibition of lipogenesis and stimulation of fatty acid oxidation. Docosahexaenoic acid (DHA) is essential for the proper functioning of our brains as adults, and for the development of our nervous system and visual abilities during the first six months of life.

DHA plays a crucial role in the growth and development of the central nervous system as well as visual functioning in infants. The inclusion of plentiful DHA in the diet improves learning ability, whereas deficiencies of DHA are associated with deficits in learning. DHA is taken up by the brain in preference to other fatty acids. The turnover of DHA in the brain is very fast, more so than is generally realized. The visual acuity of healthy, full-term, formula-fed infants is increased when their formula includes DHA.

Conditions and diseases associated with DHA deficiencies

DHA deficiencies are associated with foetal alcohol syndrome, attention deficit hyperactivity disorder, cystic fibrosis, phenylketonuria, unipolar depression, aggressive hostility, and adrenoleukodystrophy. Low levels of DHA have been associated with ADHD, Alzheimer's disease, and depression, among other diseases, and there is mounting evidence that DHA supplementation may be effective in combating such diseases. DHA deficiency plays an important role in a group of congenital diseases called peroxisomal disorders, which damage the protective covering (myelin) around nerves. Lack of sufficient DHA may be associated with impaired mental and visual functioning as well as attention-deficit hyperactivity disorder (ADHD) in children.

DHA and its companion eicosapentaenoic acid, or EPA, are also important for coronary heart disease and prevention and, in particular, in the prevention of arrhythmic events. The association of DHA deficiency with depression is the reason for the robust positive correlation between depression and myocardial infarction. Individuals with a genetic disorder known as Zellweger syndrome are known to have low levels of DHA.

Dietary sources

DHA is present in fatty fish (salmon, tuna, mackerel) and mother's milk. At present, fish oil is the major source of DHA, but alternatively it may be produced by use of microorganisms. Marine microorganisms may contain large quantities of DHA and are considered a potential source of this important fatty acid. DHA is present at low levels in meat and eggs, but is not usually present in infant formulas. Most of the DHA in fish and other more complex organisms originates in microalgae of the genus Schizochytrium, and concentrates in organisms as it moves up the food chain.

The richest dietary sources of DHA are the oils from cold water fish such as salmon, mackerel, herring, sardines, and other marine animals. DHA is also produced in the body, but it must be derived from alpha-linolenic acid, which is found in flaxseed oil.

Eicosapentaenoic acid is a polyunsaturated fatty acid that acts as a precursor for prostaglandin-3 (makes blood platelets less sticky) and thromboxane-3 groups. Eicosapentaenoic acid (EPA) is an unsaturated, 20-carbon long, omega-3 fatty acid found in fish and marine plants. EPA can be obtained by eating cold water fish such as wild salmon (not farm raised), mackerel, sardines, and herring. Most commercial fish oil preparations contain 18 percent EPA. The dietary intake of eicosapentaenoic acid has been associated with health benefits. EPA is a precursor to signalling molecules that regulate inflammation.

Eicosapentaenoic acid plays an important role in the regulation of biological functions and prevention and treatment of a number of human diseases such as heart and inflammatory diseases. Dietary supplementation with eicosapentaenoic acid (EPA) improves the prognosis of chronic inflammatory diseases, including atherosclerosis. Eicosapentaenoic acid is efficacious in glomerular diseases where mesangial proliferation is a key event. EPA lowers elevated blood pressure through the effects of series 3 prostaglandins (PCs) made from it, which block the production of blood pressure-raising series 2 PGs made from w6 fatty acids. The presence of EPA helps prevent our cells from making too many PG2 clot-forming prostaglandins.

Cyclooxygenase (COX) converts EPA intracellularly into various inflammatory mediators that may affect the bioavailability of this fatty acid for inducing apoptosis in the cancer cells.

The administration of the omega-3 fatty acid eicosapentaenoic acid (EPA) to a drug-naive patient with schizophrenia, untreated with conventional antipsychotic medication, led to a dramatic and sustained clinical improvement in both positive and negative symptoms. It is widely accepted that n-3 polyunsaturated fatty acids (PUFAs) rich in fish oils protect against several types of cardiovascular diseases such as myocardial infarction, arrhythmia, atherosclerosis, or hypertension. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may be the active biological components of these effects.

Linolenic acid is an 18-carbon polyunsaturated fatty acid with three double bonds. The isomer called alpha-linolenic acid (ALA). Another isomer of linolenic acid is gamma-linolenic acid (GLA). Gamma-linolenic acid is comprised of 18 carbon atoms with three double bonds. It is also known as 18:3n-6: 6,9.12-octadecatrienoic acid: cis-6, cis-9, cis-12-octadecatrienoic acid: and gamolenic acid. A linolenic acid deficiency will result in hair loss, poor wound healing, and scaly dermatitis.

Alpha-linolenic acid (ALA) is used as a source of energy by the body. It also serves as the parent substance to omega-3 fatty acids, compounds that regulate blood pressure, blood clotting, heart rate, blood vessel dilation, the immune response, and breakdown of fats. Additionally, alpha-linolenic acid lowers triglycerides, another blood lipid fraction which when elevated increases coronary heart disease risk. ALA may reduce the risk of heart disease by improving the arteries that carry blood throughout the body and to the brain, and by lowering cholesterol and triglyceride levels.

Essential fatty acids are also used to make brain and nervous tissue. Good sources of ALA include flax seeds, flaxseed oil, canola (rapeseed) oil, soybean oil, margarine, if made from canola or soybean oil, pumpkin, and walnuts. Alpha-linolenic acid is converted in the body to EPA (eiocosapentaenoic acid) usually found in marine oil and DHA (docosahexaenoic acid) usually found in marine fish oil.

Gamma-linolenic acid (GLA) is an important conditionally essential fatty acid (EFA). GLA is an omega-6 polyunsaturated fatty acid (PUFA). Linoleic acid (LA), another omega-6 fatty acid, is found in cooking oils and processed foods and converted to GLA in the body. GLA is then broken down to arachidonic acid (AA) and/or another substance called dihomogamma-liolenic acid (DGLA). GLA formation is dependent on the activity of the delta-O-desaturase enzyme, which is hindered by numerous factors, including aging, nutrient deficiency, trans-fatty acids, hydrogenated oils, smoking, and excessive alcohol consumption. GLA, via conversion to PGE1, exhibits anti-inflammatory, antithrombotic, antiproliferative, and lipid-lowering potential.

It also enhances smooth muscle relaxation and vasodilation. GLA may be beneficial in dry-eye conditions such as Sjögren's syndrome (a condition with symptoms of dry eyes, dry mouth, and, often, arthritis). GLA is found naturally to varying extents in the fatty acid fraction of some plant seed oils e.g. evening primrose, black currant, borage, and fungal oils. Spirulina (often called blue-green algae) also contains GLA. Dietary GLA supplementation bypasses the rate-limiting step of delta-6-desaturation and is quickly elongated to dihomo-gamma-linolenic acid (DGLA).