Omega in your Body
Fatty acids and local hormones
Polyunsaturated fatty acids
Omega-3 and omega-6 are fatty acids with more than one double bond, commonly called polyunsaturated fatty acids (PUFA). In omega-3 fatty acids the first double bond is located between the third and fourth carbon from the methyl end (CH3) of the carbon chain (see Figure 1). Omega-6 fatty acids have the first double bound between the sixth and the seventh carbon from the methyl end.
In the human body both saturated and monounsaturated fatty acids can be produced from carbohydrates and proteins. However, the human body lack enzymes to produce the essential omega-3 and omega-6 fatty acids, which must be supplied by diet. The most important of these fatty acids are linoleic acid (LA, C18:2, omega-6) and α-linolenic acid (ALA, C18:3, omega-3). From LA and ALA the body is able to produce both arachidonic acid (AA, C20:4, omega-6), gamma-linoleic acid (GLA, C18:3, omega-6), dihomogamma-linoleic acid (DGLA, C20:3, omega-6), eicosapentaenoic acid (EPA, C20:5, omega-3) and docosahexaenoic acid (DHA, C22:6, omega-3).
|Figure 1 Structure of some polyunsaturated fatty acids|
The transformation of LA and ALA to the named fatty acids proceeds through a number of desaturation (addition of double bonds) and elongation (addition of two carbon atoms) steps, see Figure 2. LA and ALA compete for the same desaturation and elongation enzymes during formation of AA, EPA and DHA. ALA is the preferred substrate in this process, but normally higher production of AA occur because of our higher dietary intake of LA compared to ALA. The formation of EPA and DHA from ALA is not efficient enough to supply the body with the required amounts of marine omega-3 EPA and DHA. Thus, these fatty acids must also be supplied directly from diet.
Figure 2 Metabolism of omega-6 LA to AA and omega-3 ALA to EPA and DHA.
In the human body local hormones and signal components are produced from AA and EPA in a process called prostaglandin synthesis. This process is initiated by oxidation of AA or EPA by cyclooxygenase enzymes (COX), producing the prostaglandins that are locally required by the body at a certain time. COX1 is the enzyme responsible to maintain the body’s normal levels of prostaglandins, while COX2 is activated when a tissue damage or infection occur. The prostaglandin synthesis take place in most cells in the body. Prostaglandins produced from AA and EPA are commonly called eicosanoids, as they have 20 carbon atoms in the molecule. The prostaglandins have from 1 to 5 double bonds, given by the number behind the PG E: PG E1 have one double bond, PG E2 have two, and so on.
PG E2 is produced from arachidonic acid (AA, omega-6), an essential fatty acid produced from LA or supplied by diet from grain fed animal meat. PG E2 is prothrombotic, stops bleeding and aid in wound healing. However, PG E2 may cause thrombosis and affect blood pressure and contraction of involuntary muscles. PG E2 is involved in all known inflammatory and pain processes in the body. To avoid chronic inflammatory situations in the body, PG E2 needs to be balanced by PG E3 produced from EPA. PG E3 has an anti-coagulation effect in blood, and has an anti-inflammatory function in the body.
Omega-6/Omega-3 balance and prostaglandin balance in the body
Production of prostaglandins are strongly affected by our diet, but also by the bodys hormone balance, health status and medication. Due to high consumption of vegetable oils and meat from grain fed animals, many people have a surpluss of arachidonic acid (AA, omega-6 ) in their body. This may result in higher PG E2 production, and an imbalance between PG E2 and PG E3 may occur locally. If such situation is sustained over time, chronic inflammation may develope and promote lifestyle related health issues. However, prostaglandin balance may be restored by changing to a diet rich in marine omega-3 fatty acids.