DHA Essential Fatty Acids

Docosahexaenoic acid, more often called simply DHA, is one of the essential omega-3 fatty acids, a type of polyunsaturated fat. Essential fatty acids can't be manufactured by the body but must come from dietary sources. There are just three omega-3 fatty acids: DHA; eicosapentaenoic acid, or EPA; and alpha-linolenic acid, or ALA. DHA constitutes 20 percent of the dry mass of brain tissue, Ocean Nutrition Canada states.

Sources

DHA must come from food or supplements, since your body can't manufacture it. The food highest in DHA is fish, particularly fatty cold-water fish such as salmon, mackerel, tuna -- especially bluefin tuna, herring, sardines and shellfish. Plant sources supply ALA, which is converted to DHA and EPA, but the conversion is inefficient, with only around 2 percent of ALA converted, Ocean Nutrition Canada reports. Supplemental omega-3 fatty acid capsules include both DHA and EPA. Supplements with a higher ratio of DHA to EPA are preferable, according to AskDrSears.com, but most supplements contain higher amounts of EPA.

Purpose

DHA plays an important role as a neurotransmitter in the brain, relaying signals between brain cells. DHA is particularly important in infant brain, nervous system and vision development in the first 6 months of life. Many commercial infant formulas now contain DHA. People who develop dementia or Alzheimer's disease are more likely to have low levels of DHA.

Benefits

Increased intake of DHA may help protect against dementia, according to a study published by researchers from the Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging in the November 2006 issue of "Archives of Neurology." Researchers looked at data from 899 men and women in the Framingham Heart Study over a 9-year period. Data showed that people with DHA levels in the top 25 percent were 47 percent less likely to develop dementia. People in this group ate fish an average of three times per week. DHA benefits the heart by reducing cholesterol and triglyceride levels, decreasing clot formation, reducing inflammation and improving blood vessel health.

Risks

Fish oil supplements normally contain both DHA and EPA; some medical practitioners recommend that infants and small children not take EPA. If you're pregnant, discuss DHA supplement use and dosage with your medical provider. People taking blood thinners or who have underlying blood disorders may develop increased bleeding tendencies when taking omega-3 supplements, which contain DHA; discuss their use with your doctor before starting. Some researchers feel that EPA, not DHA, causes increased bleeding, according to eMedTV. Diarrhea, stomach pain and fishy, unpleasant burps are also potential side effects of DHA supplements.