NUTRITION > The Omega 3 world

The World of Omega 3

Forget your fears of fat. Once you get better acquainted with them they will become your strongest allies. Fats hold about 9 calories per gram and for this reason in common dietary regimes they are often denounced. But what we often don't think about is that not all fats are the same and neither are their final destinations.

Saturated Fatty Acids and Unsaturated Fatty Acids

The first truth to uncover is the difference between saturated and unsaturated fats. The difference is so great that they can represent opposing sides when dealing with cardiovascular health. But even in the microcosmos of our cells, these fats also have different roles in the structure of our cellular membranes.

Fatty acids are usually derived from triglycerides or phospholipids. When they are not attached to other molecules, they are known as "free" fatty acids (FFA). Fatty acids can be long or short chains of carbon atoms which each bond to two hydrogen atoms and two of the adjacent carbon atoms. If the chain is completely saturated, that is to say, each carbon is bound to two hydrogens with no exception, the fatty acid becomes saturated. The molecule is strong, resistent and at room temperature the fat takes on a solid form (e.g. butter, palm fat, animal fat). If instead two (or multiples of two) carbon atoms are missing a hydrogen atom, the molecular chain is unsaturated and the two incomplete carbon atoms create a double bond (cis) with one another because of their natural tendency to form four chemical bonds. In order to create this double bond the molecule can no longer maintain its linear structure and must curve where there is an unsaturated bond, creating a sort of a mobile joint. It is for this reason that unsaturated fats such as vegetable oils assume a liquid form at room temperature. The higher the number of unsaturated bonds, the more fluid the oil. Just imagine these unsaturated bonds, double bonds that create curves between two carbon atoms. The molecule is no longer perfectly straight but takes on a three-dimensional form.

Example of saturated and unsaturated links in the Fatty Acids carbon chain

Omega 3, the Third Unsaturated Bond in a Fatty Acid's Carbon Chain

What does omega 3 mean? It simply delineates that the first cis double bond in a fatty acid's carbon chain is located at the third carbon atom. Likewise omega 6 refers to the first double bond being situated at the sixth carbon atom of the chain. Omega 9 (as in the well known oleic acid of olive oil) refers to the ninth carbon atom.
More than one type of omega 3 fatty acids exists. In all omega 3 fatty acids, the first cis bond is at the third carbon atom, each one differing in its length (number of atoms in the carbon chain) and its number of double bonds. The most important are as follows.

Alfa Linolenic Acid (ALA)

Linolenic acid (ALA) is found in vegetable sources such as flax seeds (and its derived oil), pumpkin seeds, walnuts, soy and traces are also found in leafy, dark green vegetables. It is an omega 3 fatty acid with a carbon chain consisting of 18 atoms and 3 cis bonds of which the first is obviously located at the third carbon atom: C18:3ω3.

Eicosapentaenoic Acid (EPA)

Eicosapentaenoic Acid (EPA), found mainly in cold water fish (salmon, tuna, mackerel) is a carboxylic acid with a 20-carbon chain (eicos) with five (penta) cis bonds, the first one of course located at the third atom: C22:6ω3.

Docosahexaenoic Acid (DHA)

Docosahexaenoic acid (DHA), found both in cold water fish and some algae species, is a carboxylic acid with a 22-carbon chain (docos) and six (esa) cis double bonds, the first bond located at the third atom: C22:6ω3.

EPA and DHA Derived from Linolenic Acid (ALA)

Linolenic acid is an essential fatty acid which means that our bodies cannot synthesize them but requires them for biological processes. Thus the only way to obtain them is through ingestion. Through processes of elongation (through the activity of specific enzymes called elongase) and desaturation (thanks to the enzyme desaturase), EPA is formed from these essential fatty acids and thus DHA, which is derived from EPA and can recede back to its EPA state. EPA and DHA are therefore considered semi-essential fatty acids: they are either derived from an essential fatty acid or are introduced into the body by ingestion. The difference between ingestion and derivation from linolenic acid is that the conversion process is complex and only about 10% of the linolenic acid introducted through the diet is actually converted into EPA and only a part of this in the end becomes DHA.

Linolenic Acid to  (ALA) Eicosapentaenoic (EPA) and Docosaesaenoic (DHA) Acids conversion scheme

How to Satisfy the RDA of Omega 3 Fatty Acids

To satisfy the recommended daily allowance of long-chained omega 3 fatty acids (DHA and EPA), there are four strategies: daily intake of oilseeds (ALA), a regular diet of cold-water oily fish (EPA+DHA), intake of algae-derived supplements (DHA), or the intake of distilled fish oil (EPA+DHA generally ina 2:1 ratio).
It is important to introduce omega 3 fatty acids through our diet our through daily supplements, especially during certain stages of life such as pregnancy, during breastfeeding, in the presence of heart diseases or simply during intense physical activity (e.g. sports).
It takes at least two months of proper omega 3 intake before one can note any differences. The important change takes place in the lipidic make-up of cellular membranes and this change takes time. Fish oil does not have any immediate effect so it wouldn't make sense to make use of it to block an immediate situation such as inflammation. However, modifying the lipidic make-up of cellular membranes in the long run favors the formation of anti-inflammatory mediators.

Oilseeds

The problems with oilseeds have to do with fragility of the multi-unsaturated carbon chain. The unsaturated bonds are very easily oxidized which leads to the degradation of the fatty acid. It is for this reason that oilseeds and nuts naturally have a hard, protective shell and contain antioxidants. For example, flaxseeds, if not properly chews and broken down, can transit to the intestines and if ingested in large quantity can in some cases created problems because they can get trapped in the intestinal villus. Thus flaxseeds are an important addition to any diet but only if properly chewed.
In general, for many and various reasons, proper mastication is fundamental. So it is good practice to get oneself used to chewing well.

Flaxseed Oil and How to Conserve It

Flaxseed oil should always be kept in a dark, non-transparent container in a cool place. Once opened, it should be kept in the refrigerator. It must be cold-pressed since higher temperatures cause and unreversable alteration in the oil's nutrition make-up.

Distilled Fish Oil

EPA and DHA are even more delicate. They must be conserved in containers that protect the capsules from temperature changes and antioxidants such as vitamin E are normally added to them. Fish oil supplements must be distilled several times to reduce the presence of toxic metals that are found in cold-water fish due to pollution in the environment. Furthermore, the distillation process must also guarantee that the fatty acids do not get altered. Distillation concentrates the quantity of EPA and DHA thus it is not so important the weight as it is the concentration of EPA and DHA in the oil.

DHA Supplements Derived from Algae

Algae-derived oil supplements must either be from organic sources or they must have undergone tests to check the complete absence of heavy metals (algae live on the bottom of lakes where these toxic metals deposit). Be careful also of the amount of iodine that they contain as they can cause signficant problems in certain situations such as where there is a dysfunction of the thyroid.

Omega 3 and Cardiovascular Health

Why do we talk so much about the link between omega 3 and cardiovascular benefits? As we have said in the beginning, saturated fatty acids and unsaturated fatty acids are physically very different: the former is solid, hard and stays this way even in the blood stream, thus creating the dangerous plaques that are at the root of heart diseases. These fatty acids remain solid even when they are used in building the membranes of cells, hardening these membranes and limiting the mobility of the membrane receptors. Because of this, insulin resistance is favored: insulin is not captured by the specific receptors of the membranes. The latter, the unsaturated fatty acids, are fluid and play as the substrate in creating mediators that may be anti-inflammatory, or may reduce the low density lipoproteins. We must make a distinction however between omega 3 and omega 6 since the two may end up in two very different destinations.

DHA During Pregnancy and Breastfeeding

One fact that is not often mentioned is the crucial role DHA plays during pregnancy and breastfeeding. The maximum concentration of DHA is found in the nervous system and the fetus needs DHA in forming it. The DHA is made available through the mother's diet (if she is breastfeeding) and in cases where there is not a sufficient amount of DHA available, the mother's body taps into its own reserves to assure that her child's needs are being satisfied. It has been shown that this depletion of the mother's supply increases her likelihood of being struck by post-partum depression. There are many types of DHA supplements available on the market, derived from organic algae and they are indispensable during pregnancy both for the mother and the child, and also during the entire time the baby is breastfed. Much attention is paid to taking vitamin supplements during gestation, although the efficacy of these synthetic vitamins is still being debated. Taking EPA on the other hand is not advisable especially during the first trimester. It is for this reason that algae-derived oil is recommended during gestation instead of fish oil (taking care always to check that there is no thyroid dysfunction). EPA should not be taken because it leads to a reduction in the formation of arachidonic acid (AA) which, in adults, is positive since arachidonic acid is a precursor of pro-inflammatory hormones. But for the fetus AA is of fundamental importance because prostaglandins, which are responsible for the proliferation of cells, are derived from AA.

I hope that this simplified introduction to the world of omega 3 is helpful in better understanding our diets and in leading us to making different choices at mealtime or snacktime (recommendation: snack bars made with pumpkin seeds or other mixed seeds and nuts are an excellent choice!).

16/07/2008