The Omega-3 - Basics
Omega-3: The Basics. Omega-3 are long-chained, polyunsaturated fatty acids.
Who are you calling a fatty acid? Fatty acids are the building blocks of triglycerides and other lipids. They are usually composed of a long chain of unbranched carbon atoms with a carboxyl group at one end. Most fatty acids contain between 4 and 24 carbon atoms in the backbone.
What is a saturated fatty acid? A saturated fatty acid has only single bonds in the carbon backbone. Unsaturated fatty acids have one or more double bonds in the carbon backbone. Thus, monounsaturated fatty acids have one double bond and polyunsaturated fatty acids have two or more double bonds.
These double bonds decrease the melting point - that means they are more likely to be a liquid than a solid at room temperature. The longer the carbon backbone length, however, the higher the melting point and the more likely to be a solid than a liquid at room temperature. The melting points of a series of 18-carbon fatty acids are stearic acid, 69.6 °C; oleic acid, 13.4 °C; linoleic acid, -5 °C; and linolenic acid, -11 °C.
What does omega-3 mean? Fatty acids are named by the amount of carbon atoms and double bonds in the backbone. Thus, linolenic acid, C-18:3
9,12,15, means a 18 carbon backbone with three double bonds after the 9th, 12th and 15th carbons from the "front" or methyl group. A simpler naming method only declares the first double bond from the methyl end and calls this compound an omega-3 fatty acid. This means that this fatty acid has a double bond 3 carbons from the "end" or methyl group.
What is an essential fatty acid? Omega-3 and omega-6 fatty acids are important because our bodies do not have the enzymes necessary to create double bonds after the 10th carbon from the carboxyl group. Thus, linoleic and linolenic fatty acids are essential.
Essential Fatty Acids |
Type |
Structure |
Linolenic (ALA) |
Omega-3 |
C-18:3 |
Linoleic |
Omega-6 |
C-18:2 |
ALA is the only essential omega-3 fatty acid because our bodies can convert ALA into others such as eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA). There are, however, conditions where this conversion is inefficient. For example, infants and people with certain enzyme deficiencies cannot efficiently convert ALA to EPA. For this reason, EPA and DHA are sometimes considered as conditionally essential.
The major omega-3 fatty acids are:
- ALA, (alpha) linolenic acid
- EPA, eicosapentaenoic acid
- DHA, docosahexanoic acid
The dietary requirements of essential fatty acids are approximately 2% of caloric intake for adults and 3% for children.
Where do we get omega-3 fatty acids? ALA is found primarily in dark green leafy vegetables, flaxseed oils and certain vegetable oils. EPA and DHA are found primarily in oily cold-water fish such as mackerel, herring, tuna and salmon.
Where do we get omega-6 fatty acids? Linoleic acid is found primarily in seeds, nuts, grains and legumes and thus heavily present in our diet in the form of vegetable oils (ex. corn oil) and seed oils (sunflower oil). They are also present in food items, such as mayonnaise and salad dressing, that contain these oils.
What purpose do omega-3 and omega-6 fatty acids serve? Omega-3 and omega-6 fatty acids are critical in the structure of our cell membranes and the development of the nervous system and form the foundation for the synthesis of cell mediators (prostaglandins and leukotrienies). These cell mediators play an important role in human physiology and can affect coagulation, inflammation and proliferation of certain cells.
More specifically, omega-3 fatty acids:
1. Comprise the phospholipid bilayer in the membrane of cells
2. Affect cell signaling and gene expression
3. Are primary components of brain, retina and other nerve tissue
4. Form the foundation for proinflammatory and inhibitory compounds such as Thomboxane A2
5. Play a key role in the prevention and management of chronic diseases.
The omega-6 to omega-3 fatty acid ratio and the changing western diet. In an effort to reduce cholesterol levels and lead healthier lifestyles, many Americans have substituted vegetable oils which are high in omega-3 fatty acids, in place of saturated fat from animals. This change in diet has led to an enormous increase in omega-6 fatty acid consumption and has elevated the typical omega-3 fatty acid ratio of 2:1 to 25-50:1.
The increase in omega-6 fatty acid ratio can have profound effects on an individual's health. The reason is that omega-6 fatty acids do not provide the health benefits that omega-3 fatty acids do. Although omega-6 fatty acids are an important part of the cell membrane, replacement of the phospholipids EPA and DHA (derivatives of omega-3 fatty acids) with arachidonic acid (derivative of omega-6 fatty acids) leads to a more thrombogenic state. Omega-3 fatty acids and their derivates reduce thrombogenisis by altering certain pathways leading to the production of less inflammatory mediators (prostaglandins, leukotrienes and thromboxanes). The table below highlights the general differences in health benefits between omega-3 and omega-6 fatty acids.
1. Omega-3 fatty acids reduce inflammation, omega-6 increase inflammation.
2. Omega-3 fatty acids are antithrombotic, omega-6 increase blood clotting.
3. Omega-3 are non-immunoreactive, omega-6 are immunoreactive.
These differences have profound implications for heart disease, cancer, arthritis, allergies and other chronic diseases. The scientific consensus is that the ratio of omega-6 to omega-3 fatty acids should be less than 5.
How can I get more omega-3 fatty acids? Many people desire to supplement their omega-3 fatty acid intake with dietary supplements. These supplements generally contain flaxseed oil or fish oil. DHA is commercially available in its pure form.
- Flaxseed oil contains alpha-linolenic acid but no EPA and DHA.
- Fish oil contains primarily EPA and DHA
Omega-3 from fish oil are available as triglycerides or ethyl esters. The preferred form of omega-3 fatty acids is triglycerides from fish oil. It is the most bioavailable form.