Docosahexaenoic acid, often abbreviated DHA, is one specific type of omega-3 fatty acid that is present in high amounts in cold-water fatty fish, seaweed and fish oil supplements. Omega-3 fatty acids have received a large amount of media attention for their purported health benefits, some of which is supported by data from clinical trials. As with any health supplement, you should consult your doctor before taking DHA or fish oil supplements.
Definition
Omega-3 fatty acids come in several different types, including alpha-linolenic acid, abbreviated ALA; arachidonic acid, or AA; eicosapentaenoic acid, or EPA; and DHA. Most of these compounds cannot be synthesized by your body and must be consumed from your diet. Many types of nuts and seeds, including flaxseeds and walnuts, are rich sources of ALA, while meat and poultry provide small amounts of AA. The two omega-3 fatty acids EPA and DHA, however, are only found in seafood, particularly fatty fishes like tuna, herring and salmon that live in cold water.
Dose
The Food and Nutrition Board of the Institute of Medicine recommends consuming 1.6 g of omega-3 fatty acids per day for adult men and 1.1 g per day for adult women. While the exact amount of omega-3 fatty acids vary depending on the type of fish, two servings of fish averages out to approximately 1,250 mg of DHA and EPA each day, according to the University of Maryland Medical Center, which is close to the recommended daily intake of omega-3 fatty acids. Additional omega-3 fatty acids can be provided by supplements. However, fish oil supplements can contain widely different amounts of DHA and EPA, which you should keep in mind when deciding how much extra DHA to add to your diet.
Health Benefits
Omega-3 fatty acids have numerous health benefits. In particular, DHA is found in very high levels in the brain and nervous system, suggesting that supplements containing DHA might be beneficial for cognitive function. However, a recent clinical trial found that treatment with DHA supplements did not reduce the symptoms of Alzheimer's disease, reports a study published in the November 2010 issue of the "Journal of the American Medical Association." Fish oil and DHA appear to provide beneficial effects for several other health conditions, especially heart disease, rheumatoid arthritis and Raynaud's syndrome, although additional research is needed to confirm these results.
Side Effects
Fish oil and DHA supplements are generally safe and well-tolerated, even when taken in large doses of several grams per day. The side effects that do occur tend to be mild, such as nausea, upset stomach, loose stools or diarrhea. A frequent complaint is a strong fishy aftertaste or fishy burps. Taking smaller doses of supplements spread out over time may reduce these side effects.
References
- Linus Pauling Institute at Oregon State University: Essential Fatty Acids
- University of Maryland Medical Center: Docosahexaenoic Acid (DHA)
- "Journal of the American Medical Association"; Docosahexaenoic Acid Supplementation and Cognitive Decline in Alzheimer's Disease: A Randomized Trial; J.F. Quinn et al.; November 2010
- MedlinePlus: Fish Oil
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