The omega-3 fatty acids are polyunsaturated fatty acids with powerful effects on the immune system primarily through their anti-inflammatory activity. The most potent among them are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both of which are found in fish oil.
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Areas of interest with respect to omega-3 fatty acids include autoimmune and inflammatory conditions, including cardiovascular health, various arthritic conditions, systemic lupus erythematosus (SLE), Crohn’s disease, ulcerative colitis, aging, malignancy and depressive disorders. It is noteworthy that in most of these, the patient has high levels of IL-1 and leukotriene B-4, which is produced from omega-6 fatty acids. Thus, research has focused on finding the benefits of supplementing the diet with omega-3 fatty acids.
There are mechanisms which allow omega-3 fatty acids to act both in an eicosanoid-dependent and independent manner, working rather to modulate cell signaling and gene transcription or expression. Eicosanoids are a special type of fatty acids involved in many synthetic and regulatory pathways in the body.
Later research uncovered the pro- and anti-inflammatory pathways taken by omega-6 and omega-3 fatty acids respectively. The use of vegetable oils rich in omega-6 fatty acids has increased exponentially over the last few years, changing the ratio of these fats from about 1.5:1 to about 16:1 (omega-6 to omega-3). This is suspected to be one major reason for the increasing risk of heart disease and inflammatory disease in developed nations.
The reason is that both types of fatty acids use the same enzymatic pathways for their metabolism. The omega-6 acids in general are metabolized to inflammatory compounds such as the prostaglandins and leukotrienes, while the omega-3 acids result in the synthesis of prostacyclins, which are generally anti-inflammatory in action.
The first hint of the beneficial effects of omega-3 fatty acids came from observing that the Inuit people who consumed mainly fish had low levels of blood cholesterol, especially LDL and triglycerides, which are considered markers of cardiovascular disease risk.
The cardiovascular actions of omega-3 fatty acids include:
Antithrombotic effects which reduce the risk of clot formation and embolism
Antiatherogenic effects which reduce the chances of arterial plaque disease and in turn heart attacks
Improvement in endothelial function
Reduction of blood pressure
Reduction of triglyceride and cholesterol levels
Increase in beneficial HDL cholesterol levels
Many trials using fish oil supplements have shown measurable positive effects in the course of inflammatory disorders, including a lowered need for anti-inflammatory drugs and slower progression of disease.
Again, these molecules are of critical importance in the normal functioning of cell membranes, as well as the development of the brain and the eyes. Cognitive development is improved in such infants, according to some observational studies. These molecules may also prevent preterm labor and reduce the rate of perinatal depression. Infants born to mothers who took omega-3 supplements had a lower incidence of allergies. Experts recommend a weekly intake of about 8 to 12 ounces of seafood from all kinds of fish, though other scientists think that 2-6 ounces is a safer limit to prevent fetal exposure to mercury and other neurotoxins.
Increasing the intake of omega-3 fatty acids should appear to be a foregone conclusion in view of the many advantageous effects. However, many trials have produced contrasting findings when actual cardiovascular disease incidence and mortality rates are calculated, thus leading to a significant lack of hard data on the benefits of omega-3 supplementation.
On the other hand, massive doses of these supplements are associated with an increase in the bleeding time and possibly of hemorrhagic stroke. Thus, medical advice is tempered by the lack of evidence as to the actual cost-effectiveness of adding these supplements to the diet, and by uncertainty as to whether eating oily fish is linked to adverse effects. On the other hand, some evidence of positive outcomes does exist regarding fish consumption, perhaps because of the many other beneficial elements present in fish. The safest course would appear to adopt a healthy diet and lifestyle, with appropriate portions of fish included, rather than depend on these fatty acids as a miracle cure or preventive measure.
Reviewed by Afsaneh Khetrapal Bsc (Hons)