Omega-3 and Omega-6

Omega-3 Fatty Acids

Omega−3 fatty acids, also called Omega-3 oils, are polyunsaturated fatty acids. They are widely distributed in nature, being important constituents of animal lipid metabolism, and they play an important role in the human diet and in human physiology. Omega−3 fatty acids occur naturally in two forms, triglycerides and phospholipids. There are eleven types of Omega-3 fatty acids commonly found in nature:

• Hexadecatrienoic acid (HTA)
• Alpha-Linolenic acid (ALA)
• Stearidonic acid (SDA)
• Eicosatrienoic acid (ETE)
• Eicosatetraenoic acid (ETA)
• Eicosapentaenoic acid (EPA)
• Heneicosapentaenoic acid (HPA)
• Docosapentaenoic acid (DPA), Clupanodonic acid
• Docosahexaenoic acid (DHA)
• Tetracosapentaenoic acid
• Tetracosahexaenoic acid (Nisinic acid)
  

The three types of Omega−3 fatty acids involved in human physiology are Alpha-Linolenic Acid (ALA), Eicosapentaenoic Acid (EPA), and Docosahexaenoic Acid (DHA). Among the three, ALA is considered an essential as the human body is unable to synthesise it, thus can only be obtained from the diet. EPA and DHA can be produced from ALA, albeit not very efficiently.

The most widely available dietary source of EPA and DHA is oily fish, such as salmon, herring, mackerel, anchovies, and sardines. Oils from these fishes have around seven times as much Omega−3 as Omega−6. For food sources of EPA and DHA, refer to the Codex entry for Fish Oil and Krill Oil. ALA, on the other hand, is obtained from seed oils and whole foods. For food sources of ALA, refer to the Codex entry for Alpha-Linolenic Acid.

Omega-6 Fatty Acids

Omega−6 fatty acids, also called Omega-6 oils, are also polyunsaturated fatty acids. Unlike Omega-3 fatty acids, the carbon-carbon double bond occurs in the n=6 position (i.e. the sixth bond) counting from the methyl end. The double bond in Omega-3 fatty acids occurs in the third bond. There are eleven types of Omega-6 fatty acids commonly found in nature:

• Linoleic acid (LA)
• Gamma-linolenic acid (GLA)
• Calendic acid
• Eicosadienoic acid
• Dihomo-gamma-linolenic acid (DGLA)
• Arachidonic acid (AA, ARA)
• Docosadienoic acid
• Adrenic acid
• Osbond acid
• Tetracosatetraenoic acid
• Tetracosapentaenoic acid

Within the human body, Linoleic Acid (LA), Gamma-Linolenic Acid (GLA), and Arachidonic Acid (AA) are needed for healthy development. Among the three, only LA is considered essential and must be obtained from the diet. Both GLA and AA can be synthesised from LA, albeit not very efficiently.

Vegetable oils are a good food sources of LA. For more food sources of LA, refer to the Codex entry for Linoleic Acid. Evening Primrose Oil is a good source for Gamma-Linolenic Acid.