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An Introduction to Omega 3 Fatty Acids

Fats and oils consist primarily of the triesters of a variety of fatty acids and a polyhydric alcohol (glycerol) and are thus commonly called triglycerides, although fatty acids may also be present as free fatty acids, monoglycerides, diglycerides, phospholipids, glycolipids, or sterylipids. Individual fatty acids are classified according to their degree of unsaturation, i.e. classified as saturated, monounsaturated or polyunsaturated fatty acids. Solid triglycerides are referred to as fat while liquid triglycerides are called oils.

It is generally accepted that the makeup of the fatty acids in the fat or oil can have an influence on the health (particularly cardiovascular health) of the individual
consuming them. For example, fats and/or oils high in monounsaturated fatty acids and polyunsaturated fatty acids (in particular the omega 3 fatty acids) are considered to have a positive health effect, particularly on cardiovascular health.

Omega 3 Fatty Acids Testing

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Health Claim on DHA & EPA

In 2004, the U.S. Food and Drug Administration made available a qualified health claim for reduced risk of coronary heart disease (CHD) on conventional foods that contain the omega 3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are not essential to the diet; however, scientific evidence indicates that these fatty acids may be beneficial in reducing CHD.

"Coronary heart disease is a significant health problem that causes 500,000 deaths annually in the U.S.," said Dr. Lester M. Crawford, then-acting FDA Commissioner. "This new qualified health claim for omega 3 fatty acids should help consumers as they work to improve their health by identifying foods that contain these important compounds."1

The FDA intends to exercise its enforcement discretion with respect to the following qualified 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.”

In 2000, FDA announced a similar qualified health claim for dietary supplements containing EPA and DHA omega 3 fatty acids and the reduced risk of CHD. FDA recommends that consumers not exceed more than a total of 3 grams per day of EPA and DHA omega 3 fatty acids, with no more than 2 grams per day from a dietary supplement.

Daily Value Approved for ALA

Alpha-linolenic acid (ALA) is an omega 3 fatty acid essential for human health and serves as a precursor in the human body to the formation of DHA and EPA. In 2004, the FDA approved daily values and nutrient content claims for ALA on food labels.

Based upon the Dietary Reference Intake report of the Institute of Medicine at the National Academies of Science, the minimum recommended Daily Value of ALA is set at 1300 mg. Therefore products containing more than 260 mg per serving of ALA can claim to be a "rich," "high," or "excellent" source. Products containing 130 to 260 milligrams can make a "good" source claim for ALA omega 3.

Omega 3 Content of Common Foods

Typically, EPA and DHA omega 3 fatty acids are contained in oily fish, such as salmon, lake trout, tuna, and herring. ALA omega 3 fatty acid is found in plants such as flax and oats.

Table 1: Omega 3 Foods
Food EPA mg/100g DHA mg/100g ALA mg/100g
Halibut 141 372 25
Salmon (freshwater) 709 2150 551
Tuna 1080 2290 275
Cod 64 120 3
Flaxseed 0 0 16,800
Oats 0 0 81-120
Walnuts 0 0 2100-8500

What are Omega 3 Fatty Acids?

Fatty acids are structured with a carboxylic acid group on one end, and a methyl group on the other end. Omega 3 fatty acids tend to be highly unsaturated with the terminal double bonds located at 3 carbon atoms from the methyl end.

Table 2: Omega 3 Fatty Acid Structures
Omega 3 Fatty Acid (n-3)
(carbon number:double bonds)
Common Name
C18:3* Alpha Linolenic
C18:4 Octadecatetraenoic
C20:3 Eicosatrienoic
C20:4 Arachidonic
C20:5** Eicosapentaenoic (EPA)
C22:3 Docosatrienoic
C22:5 Docosapentaenoic
C22:6** Docosahexaenoic (DHA/DCA)

*Essential fatty acid, has a daily value established so source claims can be made for foods such as "good," "high," "rich in," or "excellent" source.
**Fatty acids applicable for a qualified health claim on cardiovascular health.

Omega 3 Nomenclature

Omega (from the Greek meaning last or end) indicates how many carbon atoms from the end of the fatty acid chain the last double bond is located in an unsaturated fatty acid. The more general nomenclature for fatty acids is Cxx:y n-a, where “xx” is the number of carbon atoms in the fatty acid chain, “y” is the number of double bonds in the fatty acid chain, and “a” is the number of carbon atoms between the terminal end of the chain and the last double bond. Fatty acid carbons are always numbered starting at the carboxylic acid end of the molecule. Thus, the structure would have the designation C18:3n-3 and will go by the common name of alpha-linolenic acid.

 

The common name of “lino” refers to linen or flax, since most common fatty acid names are derived from the source in which the acid was first discovered by early chemists. For example, capric acid was first found in goat fat; palmitic in palm oil; stearic in bovine (steer) fat, etc.

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  1. AOAC Official Methods of Analysis, 996.06 https://www.fda.gov/bbs/topics/news/2004/NEW01115.html
  2. Nutrient Content Claims for DHA, EPA, and ALA (Specific Omega 3 Fatty Acids) Notification for a Nutrient Content Claim based on an Authoritative Statement. Submitted to USFDA by Olsson, Frank and Weeda, P.C. , January 16, 2004.
  3. Fats Assay-Meeting the NLEA Requirements, Lori Kjos, Rebecca Bastiaens, Dianna Martin, Stephen House, and Jonathan DeVries. Poster presentation: AOAC International, September, 1996, Orlando, FL
  4. Gas Chromatographic Determination of Total Fat, Extracted from Food Samples Using Hydrolysis in the Presence of an Antioxidant. Stephen D. House, Paul A. Larson, Rodney R. Johnson, Jonathan W. DeVries and Dianna L. Martin. JAOAC Int'l, 77 p960 (1994).
  5. Studies in Method Improvement-Official Method 996.06. Jonathan W. DeVries, Lori Kjos, Linda Groff, Bob Martin, Kristi Cernohous, Hasmukh Patel, Mark Payne, Harry Leichtweis, Mike Shay, and Leo Newcomer. Submitted for publication, Journal of AOAC Int'l.
  6. Institute of Shortening and Edible Oils, Inc., “Food Fats and Oils”, November 1992, pp.1-4