See also Flax Council.

Flax seed (also known as linseed) is one of the cheapest and highest food sources of the essential fatty acid known as alpha-linolenic acid (ALA) containing about 20% by weight.

There are two essential fatty acids that most humans cannot produce:
1. linoleic acid (LA) is an omega-6 type and is readily found in many foods; and
2. alpha-linolenic acid (ALA or LNA) is an omega-3 type (see diagram)

ALA is known technically as "all-cis-9,12,15-octadecatrienoic acid" indicating the location of the double bonds w.r.t. the head (from the left in the diagram where R is an H) and also the number of carbon atoms (8+10).

Omega-3 (aka n-3) means that, as seen from the chemical formula, the first double bond is 3 carbon atoms from the tail end. The ALA has 3 sets of double bonds. A fatty acid that has a double bond is referred to as being unsaturated because it could bond more hydrogen atoms. Clearly ALA is a poly unsaturated fatty acid, indeed it's triply unsaturated.

Animals have enzymes that can modify fatty acids at the neck end of the molecule (just after the COO) but not near the tail end. One type of enzyme (elongase) can lengthen the substance (by 2 carbon atoms) and another type (desaturase) can create new double bonds. These can form two other very important substances:
1. from LA: gamma-linolenic acid (although it does sound similar to ALA, GLA is in fact an omega-6 fatty acid), then dihomo-gamma-linolenic acid [from which type 1 prostaglandins are formed], then arachidonic acid [from which type 2 prostaglandins are formed]. Note that while animal fats are proportionately high in arachidonic acid and so promote the ratio of type 2 prostaglandins over those of type 1, GLA supplements can do the reverse (but the latter seems inefficient as some of the GLA gets converted to type 2).
2. from ALA: eicosopentanoic acid (EPA) and decoso-hexanoic acid (DHA), the so-called fish oils (also found in algae). But as we have pointed out, most humans have the enzymes to form these from ALA and even fish get there ALA from seaweeds (or by eating other fish). On the other hand, cows contain, in their fourth stomachs, bacteria which degrade the ALA so that it is lacking in both milk and in cow meat. Other animals may have ALA depending on their diets. The world is learning: Some stores now specifically sell omega-3 eggs from chickens that have been fed diets high in ALA.

Note that most fats in the diet are consumed as tri-acyl-glycerides (archaically 'triglycerides' or 'trigs') consisting of 3 fatty acids bonded to a glycerol alchohol molecule (C₃O₃H₈).

Flax seed (also known as linseed) is one of the best food sources of ALA containing about 20% by weight. It also has phyto-estrogens, a soluble fibre and a mucilagenous substance, and is high in protein (although low in lysine). Flax seed is very cheap, keeps well (the extracted oil oxidizes rapidly), and is tasty. The seed is best fresh ground (get a 'coffee grinder') and used within minutes. [Note: It makes the grinder easier to clean if you add a dry bulking agent to the flax when you grind it; I use wheat germ, but bran should not be ground.] It is good on cereal with yogourt. ALA is damaged by high temperatures (above 125 degC) so you can boil it but do not fry or bake it (although most of the material inside a baking bread does not exceed boiling temperatures). ALA also needs vitamin E to protect it in the body: flax seed has this also. (Be careful of painter's linseed oil for it may have been boiled at a very high temperature.)

Other major sources of ALA include: chia seeds (you may recall the ads for "Chia pets"), canola oil (used in many margarines but don't use those that are (partially) hydrogenated), hemp oil (marijuana), soy, seaweeds, black walnuts and small quantities are in most vegetables, especially purslane (a common garden weed in Canada that looks like mini jade plants with purple stems, oval waxy leaves, and yellow flowers).

ALA can be incorporated into the membranes of bodily cells. In doing so it adds to the mechanical property of the cellular membrane in ways that are not fully understood. ALA is mainly found in plants that grow in a northern environment and it is thought that ALA increases the flexibility of (animal) cellular membranes in cold temperature environments. It is notable that the polyunsaturates are liquid at room temperature while saturated fats are solid. ALA may increase the ability of receptors to locate into the cellular membrane while cholesterol (which normally makes up a significant portion of the membrane) may stiffen it.

More importantly, when the cellular membrane is damaged, inter-cellular enzymes convert the fatty acids into prostaglandins which act locally (while hormones like steroids act globally). There are 3 types of prostaglandins. Types 1 and 2 are derived from linoleic acid with type 1 being generally of benefit and the other type 2 often harmful. (I am trying to avoid too much detail: if interested this information can be found elsewhere.) The big discovery about prostaglandins is that aspirin (acetylsalicyclic acid, ASA) works by blocking the enzymes, cyclo-oxygenazes (COX), that catalyze these reactions. Thus, ASA blocks the good as well as the bad. Drugs that block only the type 2 have been developed (COX-2 inhibitors). If we have more ALA in our diets, the enzymes act on it to produce more of the type 3 prostaglandins. These are usually beneficial. Thus many of the benefits of ASA can come from consuming ALA. The prostaglandins are subsequently converted to other substances (e.g., leucotrienes) which affect the behavior of the white blood cells of the immune system. I originally came upon ALA by researching its effect on the immune system: it may suppress (modulate) the activity of the immune system in cases of auto-immune diseases and specifically may treat lupus (systemic lupus erythematosis, SLE). (Re: animal studies by Dr. William Clark of U.W.O. He was led to this by U.S. studies of fish oils but his research involved lignans in flax.) Contrarily: ALA does slow clotting.

Thirdly, the EPA and DHA are important in brain function and may be a deciding factor in intelligence between us and lower animals (like cows). I propose that the human brain in pre-historic times did not significantly increase in size until the beings migrated out of central Africa to the shores of the mediterranean sea with its high ALA marine life. (Since originally writing this, it has been proposed by others, such as Dr. S. Cunnane, that the source was more likely the eastern shores of African of Ethiopia.)

Dr. Johanna Budwig of Germany has done extensive research on cancer (and ALA) and suggests that many diseases are due to essential fatty acid deficiencies. Dr. Lilian Thompson at U. of T. is doing research on cancer and flax.

Essential fatty acid deficiences have also been linked to schizophrenia, bipolar disorders (archaically called manic-depression) and depression.

Studies on the Inuit who have a high fat diet, reveal little heart disease thought due to the benefits of ALA and its derivatives.

Alcoholism takes its toll by interfering with the metabolism of essential fatty acids (which also requires niacin).

A note on PG-2: The system of prostaglandins mostly has pairs that act in complementary ways. One PG-1 might decrease blood pressure (by stimulating enzymes that release NO, nitric oxide, not laughing gas) while another PG-2 might increase blood pressure. In evolution, I speculate that the body has taken advantage of the link of a high animal fat diet and the greater risk to injury of the hunting process required to get that animal fat, to use the animal fats to create systems that stimulate clotting. In a hunter society, that extra edge is useful while today's society of the 'executive hunter' has the stress that pushes that edge without the actual risk of injury. Thus the high animal fat diet in our civilization leads to unneeded clotting and hardening of the arteries. An agricultural society has a diet higher in plant fats with a lower risk of injury.

Partially hydrogenated fatty acids include trans-fatty acids (raise LDL and also lower HDL) and so are worse than saturated fatty acids (which only lower LDL). Olive oil is high in omega-9 fatty acids which are relatively neutral: not essential but not as bad as saturated fatty acids and good quality olive oil contains some ALA. Canola oil is a version of rape seed oil that also has high levels of omega-9 fatty acids (while rape is a mustard with high levels of erucic acid that has questionable benefits: normally thought harmful but (with oleic/LA) is "Lorenzo's oil" (low in DHA)). Some conjugated fatty acids (found in dairy, milk/butter/cheese) have been shown to be beneficial.

New: May need a separate source of EPA & DHA. (Link)

New: Omega 3s may lower risk of type 1 diabetes. (Link)