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What the Heck Are Eicosanoids?

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Space-filling model of the α-Linolenic acid mo...

Space-filling model of the α-Linolenic acid molecule, an unsaturated fatty acid. Colour code (click to show) : Black: Carbon, C : White: Hydrogen, H : Red: Oxygen, O (Photo credit: Wikipedia)

There is a lot of information about omega-3 fatty acids in the news and they have been the darlings of the nutrition world for quite some time now.   I first met these fascinating fatty acids in graduate school when I had to prepare a presentation for a seminar and found an article entitled “Marine Oils”.  What the heck were they?  Little attention was paid to these fats in the 1980’s.  Long story short – I ended up studying these fats as well as their counterparts, the omega-6 fatty acids,  in my research for my dissertation.

So why do we make such a big deal about getting enough omega-3s?   Basically there are three families of fatty acids – namely, sixes, nines, and threes. The nines do not participate in the production of eicosanoids as do the sixes and the threes.

We have to begin with the essential fatty acids, linoleic (omega-6) and alpha linolenic acids (omega-three).   They are called essential because they must be acquired from the diet.  Both are polyunsaturated fats. Linoleic acid is required for growth and maintenance of healthy skin and is a part of all cell membranes.  The major food sources are sunflower, safflower, corn, and soybean oils. Linoleic acid can be converted to arachidonic acid or AA (omega-6), found in meats and animal products.

Alpha linolenic can be converted at various rates to other omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).  Alpha linolenic acid is found in walnuts, dark, leafy green vegetables,  flaxseed. canola and soybean oils.  We can get EPA and DHA directly by eating fish and fish oils.

The omega-3 fatty acids:

  • Make up large parts of the brain’s cerebral cortex
  • Help form the eye’s retina
  • May benefit the health of the heart (by reducing inflammation, reducing blood clotting, and the functioning of the immune system.

This conversion rate of ALA to EPA can be slow and may depend on many factors, one being the ratio of omega-6 to omega-3 fatty acid intake.  It has been suggested that a 2.3:1 ratio of 6’s to 3’s promotes the optimal conversion of alpha-linolenic acid to EPA and subsequently to DHA.   Americans regularly eat vegetable oils but eat fish infrequently so we end up with  more omega-6s and fewer omega-3s.    Consequently, the ratio between the intake of omega-6 and omega-3 fatty acids is estimated to be  9:1 or greater.

Arachidonic acid and EPA are necessary for making hormone-like compounds called eicosanoids that participate in regulation of blood pressure, blood clotting, inflammation, and a host of other important body functions. There are four families of eicosanoids—the prostaglandins, prostacyclins, thromboxanes, and leukotrienes. For each, there are two or three separate series, derived either from an omega-3  or omega-6  fatty acid. These series’ different activities largely explain the health effects of omega-6 and omega-3 fats fatty acid families. Eicosanoids exert their influences on the cell itself rather than being transported through the blood, so their actions are local and short-lasting..

Omega-6 fatty acids produce eicosanoids that tend to favor higher blood pressure, more blood clotting, and inflammatory compounds in the body.  They are often referred to as “bad” eicosanoids.

Omega-3 fatty acids produce eicosanoids with opposing effects, i.e., lower blood pressure, less blood clotting, and anti-inflammatory effects.  They are often referred to a “good” eicosanoids.

As AA and EPA sit in the cell membrane, they use and compete for an enzyme called cyclooxygenase  to produce their eicosanoids products. Eicosanoids from omega-3 EPA can diminish the effects of the “bad” eicosanoids by producing opposing compounds that will help tip the balance back to a more favorable eicosanoid environment in the cell.

How do you help block excess arachidonic acid formation? By making sure your body has an adequate amounts of EPA that acts as an inhibitor of the enzyme (cyclooxygenase) that can produces the “bad” eicosanoids.   The higher the EPA in the diet, the more the enzyme is inhibited and the less “bad” eicosanoids are produced

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One thought on “What the Heck Are Eicosanoids?

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