What's the Deal with Flax Seed?
Plant sources of omega 3 fatty acids contain alpha-linolenic acid (ALA) almost exclusively. The omega 3 fatty acids that you really need are EPA and DHA. The body can transform ALA into EPA and DHA, but the process is really inefficient. And during that process, the excess ALA spills over into pathways that synthesize bad hormones. Clinical studies have shown that too much flax seed supplementation causes cancer (amongst other problems).
A little more explanation on this from World's Healthiest Foods:
While flaxseeds are rich in a type of omega-3 fat, they may not serve as a good source of omega-3s overall for some people. Understanding some of the basic issues involved with flaxseeds-and in fact, any kind of plant food-and omega-3 nourishment can help you to optimize your nutritional intake and your overall health.
Flax oil composition
While flaxseeds are an excellent source of omega-3 fat, they only contain one basic member of the omega-3 fat family. In the case of flaxseeds, virtually all of the omega-3 fat is found in the form of alpha-linolenic acid (often abbreviated "ALA"). This specific kind of omega-3 fat makes up about 50% of the oil in flaxseeds.
The omega-3 assembly line starts with ALA
So that you can better understand how flaxseeds that feature a concentration of ALA impacts their potential ability to be an overall good source of omega-3s, let's start with a basic chemistry review of the omega-3 family of fats.
Omega-3s are a very diverse group of fats. Yet, all of the members fall into a basic pattern that can be imagined as a kind of metabolic assembly line.
Fats can be measured in length according to the number of carbon atoms that they contain. The omega-3 fatty acid ALA, featured in flaxseeds, contains 18 carbons, making it the shortest of the omega-3 fats, and hence the simplest. It retains a position at the beginning of the assembly line with our omega-3 metabolism starting with this compound as a building block.
ALA gets elongated into other omega-3 fatty acids
If another pair of carbon atoms gets added on to ALA (a process called "elongation" in biochemistry, and a process that is carried out by enzymes called elongases), it gets ready to become EPA (eicosapentaenoic acid), another important member of the omega-3 family. If yet another pair of carbons are added to EPA, it in turn gets ready to become DHA (docosahexaenoic acid), a third important member of the omega-3 family.
ALA gets desaturated into other omega-3 fatty acids
The reason I say that these omega-3 fats "get ready" to turn into other forms is because getting longer is not the only requirement for conversion of one omega-3 to another. A second requirement is what's called "increased desaturation." During this process, the omega-3 fat gets altered chemically so that its carbon atoms are connected together in a new way that provides more reactivity to the fat. This new kind of connection is called double-bonding. For ALA (our starting point for the omega-3 assembly line) to become EPA, two new double bonds must be added in addition to the 2-carbon atom increase in length.
The role of other nutrients in omega-3 metabolism
The process of lengthening and changing, of elongating and desaturating, the chemical bonds in omega-3 fat is complex, and many nutrients are required to bring it about. To get from ALA to EPA, for example, the required nutrients are: vitamin B3, vitamin B6, vitamin C, zinc, and magnesium.
Nutrient deficiencies can block omega-3 metabolism
What happens if an individual is deficient in one or more of the above nutrients? The answer is simple: that individual cannot convert linolenic acid very efficiently into the other longer-chain omega-3 fats. A person with known deficiencies in most of the above-cited nutrients (vitamins B3, B6, C, and the minerals zinc and magnesium) would not be able to get maximum benefit from flaxseeds' omega-3s because he or she would not be able to effectively convert the ALA upward into the other omega-3 fats. Being able to effectively convert ALA upward into these other omega-3 fats is very important to our health, and when we cannot effectively accomplish this task and don't compensate by eating foods that are high in EPA and DHA, we can significantly increase our risk of health problems.
In the above situation, many healthcare practitioners would ask for an increase in the omega-3 supportive nutrients (the B complex vitamins, vitamin C, zinc, and magnesium) while at the same time also recommending a different source of omega-3s than flaxseeds, such as preformed EPA and DHA found in cold-water fish such as salmon and sardines, until the nutrient deficiencies were resolved. Yet, in cases where the assembly line seems to be functioning properly, many healthcare practitioners opt for flaxseeds and other ALA-rich foods since providing the body with the compound that is at the beginning of the assembly line allows the body to best decide the exact types and proportions of omega-3s it wants to create.