Eicosanoids

Yesterday's post on my favorite fats had prompted some questions about eicosanoids. I recommend you take a look at this chemistry post as well before we begin.

Eicosanoids are chemical messengers made from fats that contain 20 carbons. This means they are made from three fatty acids.

Eicosapentaenoic acid - This is EPA. This is one of the omega-3 fatty acids found in fish oil and cod liver oil. It has 5 double bonds

Arachidonic acid - This is an omega-6 fatty acid found in meats. It has 4 double bonds.

Dihomo-gamma-linolenic acid- This i an omega-6 acid with 3 double bonds. I am admittedly not particularly familiar with it.


The eicosanoids are one of the most complex systems in the human body. They are important in inflammation, immunity, and the central nervous system. Eicosanoids derived from the omega-6 fatty acids are generally inflammatory. Those derived from the omega-3 fatty acids are generally anti-inflammatory or have no affect on inflammation. The amounts of these eicosanoids in the body are greatly dependent on the amount of fats that they are derived from. Eat lots of omega-6 fatty acids and you'll have lots of omega-6 derived eicosanoids. This will contribute to diseases like high blood pressure, high triglycerides, and imflammatory diseases like arthritis.

There are four families of eicosanoids. They are:
-prostaglandins
-prostacyclins
-leukotrienes
-thromboxanes

So how are these eicosanoids made? They are made by the careful enzymatic oxidation of fats. Anyone who's read Nourishing traditions know that unsaturated fats should not be used for cooking because they will oxidize and can cause cellular damage. This still holds true, and the oxidation of these fats is very carefully controlled by enzymes and kept away from the nuclei of cells. Anti-oxidants can help limit the production of some of the pro-inflammatory eicosanoids There is evidence that the eicosanoid pathways evolved from the bodies attempt to detoxify oxidized fats.

The prostaglandins, prostacyclins, and thromboxanes are known collectively as the prostanoids. They ae responsible for the swelling, redness, pain, and heat associated with imflammation.

The synthesis of the omega-3 and omega-6 acids into eicosanoids involves parallel pathways, The same enzymes act on both. It is the difference in the fatty acid itself that makes the often parallel eicosanoids.

One of the most well known eicosanoid enzymes is also one of the most often used. Cycloocygenase, known more commonly ax COX, is responsible for making the prostanoids. There are three types of the COX enzyme; COX-1, COX-2, and COX-3.
Its the COX-2 enzymes that are most responsible for imflammatory omega-6 derived eicosanoids. One of the COX-1 enzyme's major functions is making eicosanoids to help blood clot.

Traditional NSAIDs such as aspirin inhibit all COX enzymes. This is one reason aspirin has a blood thinning effect as well as relieving pain. It is not selective and inhibits everything.

There are some newer NSAIDs available by prescription that inhibit only the COX-2 enzyme. You have probably already figured out that these are referred to as "COX-2 inhibitors." The problem with COX-2 inhibitors is that they have all sots of cardiovascular side ffects, and increase the risk of all sorts of heart problems. Vioxx was one of these COX-2 inhibitors. It was so dangerous it was taken off the market. Many of Pfizer's COX-2 inhibitors got on the market largely due to fraudulent research. You can read up more on this if you want. My advice is to stay far away from COX-2 inhibitors. These drug's names almost always end in "-coxib." i.e Merck's etoricoxib (Arcoxia), Pfizer’s celecoxib (Celebrex) and valdecoxib (Bextra)

The leukotrienes are the other family of eicosanoids, which more people are hearing about. Their action is implicated in inflammatory diseases such as asthma and rheumatoid arthritis, as well as asthma and allergic rhinitis. There is a drug on the market now called Singulair that is used for asthma and allergies. It works by blocking these leukotrienes.

Remember that when we talk about these broad categories of eicosanoids that its usually the ones derived from the omega-6 fats that are pro-inflammatory, and that the omega-3 ones have no effect on imflammation and may even be anti-inflammatory.

"Well thanks for all the tehnical info Zeke," you're saying, "but so what?"

These eicosanoids are one of the main reasons it is so important to pay attention to your essential fatty acid balance. If you want inflammatory eicosanoids eat more omega-6's, which isn't hard since they're everywhere these days. Soybean oils is almost all omega-6, and sunflower oil is ALL omega-6. Remember that next time you go to grab a bag of Lay's. Even though they are now trans fat free, they are now made with pure sunflower oil. Carbs and omega-6 fatty acids. It's a heart attack in a bag. The craptacular salt they use doesn't help either.

Now this isn't to say that you should cut omega-6 oils completely out of your diet. They are still ESSENTIAL fatty acids. The key is ratio's.

The proper ration of omega-6 to omega three is believed to be somewhere between 4:1 and 1:1. Studies have shown that the Eskimos ate extremely high fat diets with rations of 1:30 without ill effects. It seems that an excess of omega-6 is bad, but that if the ration is swung the other way with high omega-3's there is no observed ill effect. The typical American eats a ration of 10:1 up to a 30:1 ratio. This is the exact opposite of what the Eskimos ate/eat and we have health as terrible as their's isn't. For your reference, here is a list of some common oils and their fatty acid ratio's shown as the ratio of omega-6 to omega-3

flax 1:3
canola 2:1
olive 3–13:1 (be aware that olive oil can vary from a great ratio to a bad radio. Always read the label.)
walnut 4:1
soybean 7:1
corn oil 46:1
sunflower 1:0 (no omega-3)
cottonseed 1:0 (almost no omega−3)
peanut 1:0 (no omega−3)
grapeseed oil 1:0 (almost no omega−3)

For more reading I suggest the works of Udo Erasmus and Mary G. Enig. Also the wikipedia article on eicosanoids is very good.

This article is part of Fight Back Fridays at Food Renegade. Check it out! Its a great blog.