Just What Is Omega-3

Known primarily as the beneficial component of fish oil, Omega-3 polyunsaturated fatty acids (PUFAs) come in different varieties and sources.  I don’t know about the stuffed shirts, but I like to say “poof-a.”  I will probably work poof-a into conversation a number of times this week.  Anywho, the PUFAs we call omega-3 have shown a lot of promise for neuroprotection, which we will look at in future articles.  Here and now, we try to better understand something we’ve been hearing about for years.

Let’s Talk About Fat

Triglycerides.  Our body fat is made of triglycerides.  Triglycerides are also found floating in our blood.  Triglycerides are made from a backbone of glycerol (also called glycerin) and 3 to 4 fatty acids.  Glycerol is a colorless, odorless, sweet, and non-toxic liquid.  Fatty acids are where all the variety comes in.

Fatty acids are usually 16, 18, or 20 carbon atoms long and most importantly fatty acids are either saturated or unsaturated.

Saturated.  Imagine 16 people (carbon atoms really) holding hands as a chain.  Each person is touching the person next to them only once (hand in hand).  Each person in this chain is also wearing a hat made of hydrogen (I like to think of it as a knit cap, but it’s really up to you).  This group is saturated.

Unsaturated.  Now image a similar chain except that two or more people are not wearing hats.  Instead they are contorting until their heads touch (forming a double bond – hand in hand and head to head).  Not everyone has a hydrogen hat so it is unsaturated.

Solid or Liquid.  Saturated chains of carboxylic acid (those chains of imaginary people holding hands) where everyone is wearing a hat are more likely to be solid at room temperature because the chains can be packed close together.  Unsaturated chains cannot be as closely packed because of the kinks and bends in the chains formed by the contortions needed to touch head to head, therefore unsaturated fatty acids are more likely to be liquid at room temperature.

The numeric designations used for fatty acids come from the number of carbon atoms, followed by the number of sites of unsaturation (head to head).  For example , palmitic acid is a 16-carbon fatty acid with no unsaturation (everyone has a hat) and is written 16:0.

Palmitoleic acid is a 16-carbon fatty acid with one site of unsaturation (head to head) therefore it has the designation 16:1.  This designation gets even more precise and can indicate the location in the chain where the hats are off.  Again palmitoleic acid has 16 carbon atoms in a chain and 2 atoms are touching heads (point of unsaturation).  The double bond occurs at atoms 9 and 10 so the designation becomes 16:1^Δ9.

PUFA. Most fatty acids are acquired through our diet.  We can make fatty acids in the body except for two that we can only attain through our diet.  They are linoleic acid and α-linolenic acid and they are both poly-unsaturated-fatty-acids (hyphens added for emphasis) also known as PUFAs.  Poly of course meaning many, so these fatty acids contain more than one hat-less couple (point of unsaturation).

Essential.  The two fatty acids we can’t make (linoleic acid and α-linolenic acid) are called essential fatty acids because they can only be acquired through our diet.  Plants can synthesize linoleic and α-linolenic acid, so we can get our PUFAs by eating a variety of plants or by eating the meat of animals that have eaten these plants.

Omega 3 vs 6.  Linoleic acid (18:2^Δ9,12) is an omega-6 PUFA and α-linolenic acid (18:3^Δ9,12,15) is an omega-3 PUFA.  Look at the numbers after the delta that tell you where the unsaturated atoms are in the chain.  Linoleic acid is unsaturated at positions 9 and 12.  That last number is the key to understanding omega-3 vs omega-6.  Subtract the last number from the total number of carbon atoms – for linoleic acid that would be 18-12=6 hence omega-6.  Alpha-linolenic acid would be 18-15=3 therefore it is omega-3.  Omega because we are looking at the “last” or furthest point of unsaturation.

• EPA- Eicosapentaenoic acid (20:5^{Δ5,8,11,14,17})
• DPA – docosapentaenoic acid (22:5^{Δ7,10,13,16,19})
• DHA – docosahexaenoic acid (22:6^{Δ4,7,10,13,16,19}).

ALA – the mother of all omega-3’s.  The omega-3 PUFA series begins with α-Linolenic acid (ALA).  The three omega-3 PUFAs that everyone talks about (EPA, DPA, and DHA) are all derived from ALA.  This actually can be done in the body, but the conversion of ALA to EPA requires three independent reactions.  The conversion of EPA to DHA requires four more reactions. This process is even more inefficient in individuals consuming a typical Western diet rich in animal fats.  This information isn’t critical, but if it comes up at a party you’re covered.

Fish oil.  Omega-3’s show up in all sorts of food, but EPA and DHA are concentrated in fish fat and fish oils and thus do not need to undergo the complex conversion steps required of ALA.

Other Sources.  All three omega-3’s listed above are also found not only in fish, but also in seafood, certain omega-3 supplements and to a lesser extent in meats and poultry.  Human milk contains small but significant amounts of PUFA, particularly AA (again this is an omega-6) and DHA that are necessary for optimal development of the brain.  Egg yolk is a good source of PUFAs, especially DHA.

ALA is found in these common foods: Raspberry (Red and Black), Blueberry, Cranberry, and Basil.  Surprisingly, some other omega-3’s show up in edible weeds.  The only one I was familiar with was pigweed, of which, the variety Amaranthus viridis turns out to be used in traditional medicine and contains ALA and EPA.