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[2008 updates are highlighted in red]
| Description: |
This approach increases the intake of omega-3 fatty acids, which include eicosapentanoic acid (EPA), docosahexanoic acid (DHA), and alpha-linolenic acid (ALA). EPA and DHA are present in relatively high levels in fish, especially fatty fish such as salmon, Atlantic herring, Atlantic mackerel, bluefin tuna, and sardines. Dietary supplements containing EPA and DHA include fish oil and cod-liver oil. Rich sources of ALA include flaxseed oil, canola oil, and walnut oil. |
| Rationale: |
The rationale for this approach is similar to that outlined for the Swank diet and supplementation with omega-6 fatty acids (see above, under “Swank Diet” and “Supplementation with Omega-6 Fatty Acids”). In addition, immunologic studies indicate that, among the polyunsaturated fatty acids (PUFAs), the omega-3 fatty acids exert the most potent anti-inflammatory and immune-modulating effects. Also, omega-3 fatty acids appear to be important in forming and maintaining myelin, a part of the nervous system that is injured in MS.
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| Evaluation: |
Studies of omega-3 fatty acid supplementation in the animal model of MS are limited and conflicting. The most rigorous clinical study of this approach was a placebo-controlled trial of fish oil in people with RRMS. There was a trend for the treated group to show less disease progression, fewer attacks, and decreased attack duration, but these findings were not statistically significant. Therapeutic effects were noted in two uncontrolled studies, one with cod-liver oil, calcium, and magnesium, and the other with fish oil, other dietary supplements, and dietary advice. A small study evaluated omega-3 fatty acid supplementation in combination with interferons or glatiramer acetate. People were treated with their MS medications along with either fish oil and a very low-fat diet or with olive oil and a low-fat diet. There was a trend for improved physical and emotional functioning in those taking fish oil. Both dietary interventions were associated with a decrease in relapse rate. |
| Risks: |
Supplementation with modest doses of fish oil is generally safe. In the United States, the Food and Drug Administration (FDA) has classified fish oils as “generally regarded as safe.” A seven-year study of fish oil use in nearly 300 people did not find any serious side-effects. The long-term safety of other omega-3 fatty acid supplements is not known. Increased dietary intake of ALA may increase the risk of prostate cancer. Although fish oil supplements generally do not have a significant amount of mercury, some fish, such as shark, swordfish, and king mackerel, do contain relatively high mercury levels. Fish and flaxseed oil may have a blood-thinning effect. Fish oil may impair lung function in those who are aspirin-sensitive. High doses of fish oil may increase blood sugar levels in diabetics. High doses of flaxseed oil may produce cyanide toxicity. There are potential side-effects that are specifically associated with cod-liver oil (see above, under “Swank diet”). For women who are pregnant or breastfeeding, the safety of omega-3 fatty acid supplements, including fish oil, is not known. |
| Costs: |
Supplementation with omega-3 fatty acids is inexpensive. |
| Committee opinion: |
In the opinion of the Committee, omega-3 fatty acid supplementation is inexpensive and generally well tolerated. In limited MS studies, this approach has produced suggestive, but not definitive, therapeutic effects. A preliminary report indicates a possible beneficial effect of fish oil supplements in combination with interferons or glatiramer acetate. Further study of omega-3 fatty acid supplementation is needed to determine whether it is definitely effective in MS and whether it is safe and effective in combination with disease-modifying medications.
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