In biochemistry, a fatty acid is a long hydrocarbon chain. The carboxylic -COOH cap makes these molecules acids. Fatty acids that have carbon–carbon double bonds (C=C) are known as unsaturated. Fatty acids without double bonds (C-C) are known as saturated.
The fatty acids have two ends:
- the carboxylic acid (-COOH) end is considered the beginning of the chain, thus “alpha”
- the methyl (-CH3) end is considered the “tail” of the chain, thus “omega”.
Why some fatty acids called Omega-3
The way in which a fatty acid is named is determined by the location of the first double (C=C) bond, counted from the methyl end, that is, the omega (ω-) or the n- end. Omega-3 fatty acids have this double bond at the third carbon atom from the end of the carbon chain. Omega numbering could be ω−3, ω−6, ω−7, and ω−9. So, the name comes from the chemical structure. Just take a look at the chemical structure of alpha-linolenic acid (ALA) that has a chain of 18 carbons with a double bond at the 3rd carbon from the “omega” end.
Chemical structure of alpha-linolenic acid (ALA)
There are three omega-3 fatty acids that are involved in human physiology:
- alpha-linolenic acid (α-linolenic acid – ALA) – comes from plant sources
- eicosapentaenoic acid (EPA) – comes from animal sources
- docosahexaenoic acid (DHA) – also comes from animal sources
Essential fatty acids
Omega-3 and omega-6 are called “essential fatty acid” because they are necessary for good health, but cannot be produced within the human body. We can get them only through diet.
- ALA – Alpha-linolenic acid is found in plant seeds, nuts (notably walnuts), and many common vegetable oils. Seed oils are the richest sources of α-linolenic acid, notably those of chia, flaxseed (linseed oil), rapeseed (canola), and soybeans.
- EPA and DHA – Marine animals such as fish and krill provide eicosapentaenoic acid and docosahexaenoic acid.
As we have said above, α-Linolenic acid can only be obtained by humans through their diets; it cannot be de novo synthesized from stearic acid in the body. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are readily available from fish and algae oil and play a vital role in many metabolic processes.
Most of the health benefits of omega-3 fats are linked to the animal-based EPA and DHA, not the plant-based ALA. The human body has a limited ability to convert ALA into the longer-chain omega-3 fatty acids — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which means that even if you consume large amounts of ALA from plant sources, your body can only convert a relatively small amount into EPA and DHA.
People who follow a Mediterranean-style diet, which includes whole grains, fresh fruits and vegetables, fish, olive oil, garlic, and moderate wine consumption, tend to have higher level of good cholesterol, which help promote heart health.
It’s a scientifically proven fact that Inuit Eskimos, who tend to have a high fat diet, but eat significant amounts of fatty fish rich in omega-3 fatty acids, have lower risk of cardiovascular system problems and even reduced rates of colorectal cancer.
Ideally, what you need to do is include animal-based omega-3 fatty acids in your diet.
- http://jama.jamanetwork.com/article.aspx?articleid=185895 (Fish Consumption and Risk of Sudden Cardiac Death)
- http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0396.2011.01135.x/abstract (A krill oil supplemented diet reduces the activities of the mitochondrial tricarboxylate carrier and of the cytosolic lipogenic enzymes in rats)
- http://articles.mercola.com/omega-3.aspx (Your Practical Guide to Omega-3 Benefits and Supplementation)