There are very few sources of EPA in the diet. It can be made from the omega-3 oil alpha-linolenic acid found in large amounts in flax oil, in moderate amounts in canola oil and walnuts or in small amounts in green leafy vegetables. Only about 3 – 5% of the alpha-linolenic acid consumed becomes EPA or DHA in healthy individuals. This process is hindered in various disease states and requires that some people get EPA from their diet or supplementally.
The average American's diet, however, is now low in EPA, resulting from a declining consumption of dietary sources of EPA such as fatty fish and animal organ meats. Vegetarians have lower blood levels of EPA due to its absence in foods of plant origin. There is now an algae-derived oil that has both DHA and EPA, suitable for vegans and vegetarians. Fish obtain their DHA and EPA ultimately from the consumption of algae.
Fish oils contain both EPA and DHA in varying ratios, usually with about twice as much EPA as DHA. Some conditions are treated predominantly with EPA and others with DHA. Since EPA and DHA seem to compete with each other, taking a blend of the two has proven not to produce the expected benefits in some conditions. In other words, DHA should be taken separately from EPA in some conditions and a high EPA /DHA ratio product should be used in other conditions.
A study on elderly Japanese patients demonstrated that blood levels of the omega-3 fatty acids EPA and DHA increase after prolonged consumption of ALA from a plant-based oil. The change is slow and requires about 10 months of supplementation. However, the result of the study suggests that supplementation with ALA from flax oil may to some degree have the same beneficial role as supplementation with fish oil. This news may be particularly interesting to people following a vegetarian diet or for those who do not eat fish products. [Journal of Nutritional Science Vitaminol, December 1999]
Sources with a high EPA/DHA ratio are prepared from fish oils. There is currently no product available which contains EPA without any DHA. Supplemental sources with high DHA/EPA ratios are now available that have been derived from algae. Eggs are now available which contain EPA and DHA when the chickens have been fed special diets containing these fatty acids or flax seed. Therapeutic EPA doses are in the range of 500 to 2,500mg per day, depending on the condition being treated.
There is an increasing body of evidence that indicates that fish oils, in particular those with high EPA to DHA ratios, have a major role to play in helping people maintain good mental health and to avoid mood swings and mild depression. Currently the only available source of EPA without equal amounts of DHA being present is "EPA rich" fish oil.
Several studies have shown that essential fatty acids may be beneficial in treating Bipolar Disorder. The omega-3 metabolite responsible is believed to be EPA. At least one study found DHA, the other common metabolite, to be ineffective. [Omega-3 Fatty Acids in Bipolar Disorder: A Preliminary Double-blind, Placebo-controlled Trial. Arch Gen Psychiatry. 1999;56: pp.407-412]
Several double-blind clinical studies have demonstrated that supplementing the diet with 10 to 12gm of EPA results in significant improvement. This would be equivalent to the amount of EPA in about 150gm of mackerel or herring. It must be kept in mind that the presence of DHA in fish oil may reduce the effectiveness of the EPA. A high EPA fish oil is recommended.
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