Vitamins, Minerals and Dietary Supplements
What is DHA?
DHA is short for docosahexaenoic acid. It is a type of fatty acid that belongs to a class of substances called essential fatty acids. It is produced naturally by the body, and is also present in a wide range of foods.
DHA has been shown to reduce levels of potentially dangerous substances called triglycerides in the bloodstream. Studies have shown that it can be just as effective as fish oils in lowering triglyceride levels in people at risk for heart disease. It also plays an important role in the prevention of a group of nervous disorders such as Zellwegger's syndrome, which damage the myelin sheaths surrounding nerve cells and is potentially fatal to infants. Double-blind studies have also shown that DHA may improve brain functioning in babies, and may help to manage some autoimmune disorders, such as lupus and rheumatoid arthritis. There is also evidence that children with attention deficit disorder and other childhood diseases may have low DHA levels, and may benefit from DHA supplementation.
How much DHA should I take?
Because DHA is a naturally occurring substance, most healthy people do not take DHA supplements. However, most studies of DHA supplements have used doses ranging from 1 to 3 grams per day, usually derived from fish oil.
What forms of DHA are available?
DHA is found primarily in cold-water fish such as mackerel, salmon, sardines, herring, anchovies and albacore tuna. Cod liver oil contains large amounts of DHA and a similar fatty acid, EPA. Vegetarians can obtain DHA from certain microalgae. DHA is also available as a supplement, usually in capsule or extract form.
What can happen if I take too much DHA? Are there any interactions I should be aware of? What precautions should I take?
Premature infants who are not breast-fed are usually deficient in DHA; as such, DHA supplementation is recommended in these individuals. Patients with a history of heart disease should consult with their health care provider after taking fish oil supplements for several months, as this may lead to increased blood sugar levels. In addition, while DHA appears to treat some autoimmune disorders, it does so by decreasing the activity of certain immune cells. As a result, patients with autoimmune disorders who are taking large doses of DHA may be at increased risk of infections.
As of this writing, there are no well-known drug interactions with DHA. As always, make sure to consult with a licensed health care provider before taking DHA or any other herbal remedy or dietary supplement.
- Davidson MH, Maki KC, Kalkowski J, et al. Effects of docosahexaenoic acid on serum lipoproteins in patients with combined hyperlipidemia: a randomized, double-blind, placebo-controlled trial. J Am Coll Nutr 1997;16:236-43.
- Kelley DS, Taylor PC, Nelson GJ, et al. Docosahexaenoic acid ingestion inhibits natural killer cell activity and production of inflammatory mediators in young healthy men. Lipids 1999;34:317-24.
- Makrides M, Neumann MA, Gibson RA. Is dietary docosahexaenoic acid essential for term infants? Lipids 1996;31:115-9.
- Martinez M, Vazquez E. MRI evidence that docosahexaenoic acid ethyl ester improves myelination in generalized peroxisomal disorders. Neurology 1998;51:26-32.
- Nelson GJ, Schmidt PS, Bartolini GL, et al. The effect of dietary docosahexaenoic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans. Lipids 1997;32:1129-36.