ANSWER

There are three types of omega fatty acids: omega–3, omega–6 and omega–9.

Omega 3

Omega 3 is the essential n-3 polyunsaturated fatty acid that cannot be made in the body and must be obtained from a diet. Alpha-linolenic (ALA), Eicosapentaenoic (EPA) and Docosahexaenoic (DHA) acids are the three most common omega 3 fatty acids found in foods. Omega-3 fatty acids can help lower the risk of chronic diseases such as heart disease, stroke and cancer as well as lower LDL or “bad” cholesterol (Rindfleisch, 2007).

Figure 1: The Structure of Omega 3

FDA
FDA has listed omega-3s on the Generally Regarded as Safe (GRAS) list, but recommended that consumers not exceed a total of 3 g of omega-3s per day, with no more than 2 g per day from dietary supplements.

Health claim: “Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease. One serving of [name of food] provides [x] grams of EPA and DHA omega-3 fatty acids. [See nutrition information for total fat, saturated fat and cholesterol content.” (U.S. Food Drug Administration, 2004).

Alpha-linolenic acid (ALA)

ALA is an 18-carbon chain and three cis double bonds. The first double bond is located in the n-3 position or at the omega end of the fatty acid. ALA’ primarily functions as a precursor for the synthesis of EPA which in turn forms DHA but may also have an independent role in protection against coronary heart disease via different mechanisms. Conversion of ALA to EPA and DHA is limited and varies according to the intakes of other fatty acids (University of Colorado Colorado Springs, n. d.).

Source: Flaxseed, canola and soybean oils, and walnuts.

Docosahexaenoic (DHA) and Eicosapentaenoic acid (EPA)

DHA plays an important role as a structural membrane lipid, particularly in nerve tissue and the retina, and can also act as a precursor to certain eicosanoids. Diets high in EPA and DHA help with brain and eye development, prevent cardiovascular disease, and can help to prevent Alzheimer’s disease. Fish oil and fatty fish such as salmon, mackerel, herring and tuna are the primary sources of EPA and DHA. Algae oils are a vegetarian source of DHA (University of Colorado Colorado Springs, n. d.).

Source: Marine – Fatty fishes such as mackerel, herring, salmon, tuna and trout; Plant – Algae.

 

Omega 6

Omega 6 is an essential polyunsaturated fatty acid. Linoleic acid (LA), Gamma-linolenic acid (GLA) and Arachidonic acid (AA) are the common types of omega 6. Primary sources are liquid vegetable oils, including soybean oil, corn oil and safflower oil (University of Colorado Colorado Springs, n. d.).

Figure 2: The Structure of Omega 6

Linoleic acid (LA)

It is a carboxylic acid with an 18-carbon chain and two cis double bonds with the first double bond located at the sixth carbon from the omega end of the fatty acid.

Source: Soybean, sunflower, corn, peanut and safflower oils.

Arachidonic acid (AA)

It is a carboxylic acid with a 20-carbon chain and four cis-double bonds. It is used to synthesize regulatory molecules such as prostaglandins (hormone like chemical messengers) and thromboxanes (involved in platelet aggregation and blood clotting).

Source: Red meat, poultry and eggs.

Gamma-linolenic acid (GLA)

It is a carboxylic acid with an 18-carbon chain and three cis double bonds. It is an isomer of α-linolenic acid, which is a polyunsaturated n-3 (omega-3) fatty acid.

Source: Infrequently consumed vegetable oils, such as evening primrose oil; mostly found in nutritional supplements.