At one time supplements of EFAs were basically the only way to improve
EFA status easily.

Flax oil
Evening primrose/borage/black currant oils
Fish oils

When we started this in our home, I was taking and having my son take,
one cap of each. This was a long time ago.

Now we have many food choices available to us, to make this easier.
I get my ALA Omega-3 from food now. But I do use fish oil now and then,
for my arthritis flares. But not everyday, anymore.

Flax oil is very unstable and oxidizes easily/quickly. Caps should be stored in the frig like the liquid oil itself. Flax oil is the basic essential fatty acid that we need to have every day. The ratio between Omega-3 and Omega 6 should be as close to 1:1 up to 1:5 as possible. In USA the Omega-6 consumption is quite high, so people typically do not need to supplement it. In fact they need to cut back on it some so the ratio becomes closer. The advantage to using flax oil, is that it is the FIRST ingredient in a long chemical sequence for the synthesis of compounds useful to the body. Some is eventually converted to EPA and DHA, but the intermediate uses are also important. People with poor skin/acne, dry skin, mouth sores, etc do well on flax oil supplements.
Flax liquid oil itself tastes better than other oils, and mixes well into food.
You can mix it with cottage cheese, equal parts with butter melted and resolidified makes a good spread, mix into drinks/smoothies, mix with salad dressing ingredients like Good Season's for salads. Now we have several food choices that do this for you. Smart Balance peanut butter has 1000mg of flax oil in each tablespoon. Smart Balance spread also has this done for you.

Evening Primrose oil provides the GLA that is necessary for conversion to long chain fatty acids.

Evening primrose oil has been the most commonly used, and sometimes in high doses. I found however, that only a little of this goes a long way. Really high doses can cause diarrhea. Also there is concern for those with seizure disorders that it MAY (rarely) increase seizure frequency. But the only really documented cases came from those taking antipsychotic drugs and high dose primrose. And these were not many.

At one time very high doses of primrose (or the others supplying GLA) were
used for PMS control, or other female menstrual problems. One can search the net and find many older articles about its various uses.

If you are really aggressive about this subject you can have a fatty acid
blood profile done. Some parents on OBT on the Tourette's board did that years ago. I recall two posts from parents where GLA was found very low or lacking. People vary genetically in the expression and metabolism of fatty acids. There are so many steps and enzymes to go thru, that errors can occur. So testing may be a very good tool if you can have it done.
For example in folate chemistry (a B-vitamin) there have been 25 genetic errors found in folate methylation, so far. So it is very possible that subtle errors in EFA chemistry also lead to disease states as well.

The EPA and DHA definitions are well explained on the post before this.

I contacted EFAMOL corporation years ago and asked about the AA content in their Efalex product. This was the only fish oil product that listed on the label the AA content (arachidonic acid). They answered me that ALL fish oils contain trace amounts of this long chain fatty acid, and it is not removed by distillation/purification processes.
AA is a fatty acid that is very important to developing nervous systems..the fetus, infants and small children. It is included in baby formulas now in this country. However, in huge amounts, it is a precursor to vasoconstriction and
platelet clumping...ie. heart attacks. There are no AA supplements for adults.
However it is common in some foods. Meats, chicken, turkey, eggs are the prime sources. The higher the fat content the higher the AA content. AA levels are lower in Omega-3 eggs.

Here is another complex article on AA..:
http://www.acnp.org/G4/GN401000059/CH059.html

So while supplements do exist, and we use some of them still in our home,
our culture has changed, and provides now food sources to enable people to enrich their diet and not need to swallow capsules of most of the EFAs.

If you want significant anti-inflammatory actions, high dose fish oil may be the only way to go. Eating fish will not provide enough for some conditions. Really high dose use however, should be supervised by a doctor. Fish oil has some anti-clotting effects, and
can interfere with some drug therapies and other treatments. The highest physican supervised patient I have seen was a 12gram/day dose. This was to treat an autoimmune kidney disease/failure (which it succeeded in preventing kidney failure).

edit: 1-29-14....
many links I used to have in this thread have been removed from the internet. They may be still there with new addresses, but that is difficult to find today.

This link to Linus Pauling Institute in Oregon is quite good:
http://lpi.oregonstate.edu/infocente...nuts/omega3fa/

and
http://lpi.oregonstate.edu/ss11/fats.html

http://www.biologicnr.com/fatty-acids-101/

http://drbenkim.com/articles-omega-3-fatty-acids.htm

This is a link to Thorne about GLA specifically:
http://www.thorne.com/altmedrev/.fulltext/9/1/70.pdf