Docosahexaenoic acid better known as DHA is an omega-3 long-chain polyunsaturated fatty acid. Although adequate amounts of DHA are especially important during the perinatal period, this essential fatty acid (EFA) plays a vital role in the maintenance of effective brain function throughout life. Up to 45% of the fatty acids in synaptic membranes are composed of EFAs. Adequate DHA intake is necessary for optimal synaptic function. One of the most significant areas of DHA research involves infant brain development. The human brain grows rapidly during the late stages of fetal development and early infancy.

The DHA content of the fetal brain increases 3-5 times during the final trimester of pregnancy and triples during the first 12 weeks of life. Premature infants and those who are not breastfed are at increased risk of DHA deficiency. Normal development of the retina and the visual cortex also depends on adequate DHA levels. The retina develops rapidly during the final months of pregnancy and in the first 6 months of infancy. A correlation exists between low levels of DHA and certain behavioral and neurologic conditions associated with aging, such as dementia, depression, memory loss, and visual problems. Low DHA levels may also play a role in the development of attention-deficit/hyperactivity disorder (ADHD).

Sources of DHA

In the perinatal period, DHA is supplied by the placenta and, subsequently, by breast milk. Later in life, foods such as fish, organ meats, and eggs are the primary sources. Because significant brain and eye development occurs in utero and continues during the first year of life, it is crucial for preconceptual, pregnant, and lactating women to maintain optimum levels of DHA to ensure that proper amounts are available when needed. However, the DHA content of the average American’s diet, which is already low, continues to decline. Ironically, as people have been striving to improve their diets by eating fewer high-fat foods, they have also been consuming decreased amounts of DHA containing nutrients. The DHA level in the breast milk of the average American woman is among the lowest in the world. A primary reason: Most Americans don’t eat enough fresh fish and are consuming less red meat and fewer eggs.

Although an important source of DHA is fresh fish, the purest source is not the fish itself but the marine phytoplanktonmicro-algaethat the fish eat. Cold-water fish tend to contain high concentrations of DHA, and health care professionals need to relay the message that not all fats are detrimental to health. Good sources of DHA include mackerel, Atlantic salmon, bluefish, halibut, herring, sockeye salmon, striped bass, tuna, Atlantic cod, and flounder. Adequate levels of DHA can be maintained by consuming 2-3 servings of fresh fish per week. A caveat: The fish cannot be fried because the oil used in frying replaces the EFAs.

The Perinatal Period

Brain development peaks during the last trimester of pregnancy and the first 18 months after birth. The fetus acquires DHA via the placenta; during the early postnatal period, breast milk is the primary natural source of DHA. In most European and Asian countries, manufacturers of infant formula include DHA in their products to ensure optimum neurologic development for children who are not breastfed. It is disturbing that no formula available in this country contains DHA. Establishing a minimum requirement for DHA in infant formulas would provide the same benefits for U.S. babies that are presently enjoyed by babies in Europe and Asia.* DHA is retained in the brain except during two critical periods: During pregnancy and lactation, DHA is transferred to the placenta and then to breast milk. DHA levels in human breast milk depend on the mother’s diet. The breast milk of many European women contains about twice as much as that of American women, and Japanese women have about three times as much. A decline in the DHA content of breast milk has also been reported among women in the United Kingdom and Australia.

The IQ of breastfed babies tends to be higher than that of babies fed non-DHA-containing formulas, and even a small reduction in IQ has important socioeconomic implications. The cost of potential problems associated with DHA deficiency by far outweighs the cost of supplementing formula. Adding to formulas an amount of DHA that matches the optimum levels contained in human milk would provide American babies with an adequate supply. The World Health Organization recommends that preterm baby formulas contain enough DHA to supply 20 mg/kg/d of DHA and that term formulas contain enough to supply 40 mg/kg/d.

DHA Supplementation

The consumption of fish, game, organ meats, and eggs has been declining in recent years, and a vegetarian diet is usually low in DHA. Eggs contain at least some DHA, and if vegetarians are not eating these either, their intake of DHA is essentially nonexistent. Many adults and children might thus benefit from DHA supplementation. Techniques have been developed to extract DHA from phytoplankton. The oil in these microscopic plants contains DHA similar to that contained in human breast milk and cold-water fish. DHA supplements are available in health food stores.

DHA Deficiency and Disease

The body’s ability to synthesize DHA may decrease with age. Studies on nutrition in the elderly suggest that many conditions associated with aging, such as sensory deficits and forgetfulness, may be minimized or avoided if a nutritious diet that includes adequate amounts of DHA is maintained. Some authorities believe that cognitive deficits and dementia may be associated with poor nutrition and that many undesirable age-associated changes, such as a decline in energy, anorexia, and diminished sensations of taste and smell, can be arrested and even reversed by a well-balanced diet. DHA is the building block of human brain tissue and the primary structural fatty acid in the gray matter of the brain and the retina. Development of the retina and the visual cortex depends on adequate DHA levels. Autosomal-dominant retinitis pigmentosa has been linked with reductions in DHA concentrations in the retina.

Alzheimer’s Disease

The maintenance of adequate DHA levels may be important for optimum neurologic function throughout the life span. It has been noted that there is a correlation between DHA deficiency and the incidence of Alzheimer’s disease (AD). A 10-year prospective study of more than 1,000 elderly persons indicated that a low DHA level is a significant risk factor in the onset of dementia. The brains of patients with AD have significantly lower levels of DHA and arachidonic acid another EFA than the brains of healthy elderly people. Further research may be required to determine the beneficial effects of DHA supplementation in elderly patients.

Depression

A documented increase in depression in North American has occurred within the last century, during which consumption of DHA declined. The World Health Organization predicts that by 2020 major depression will be the greatest cause of lifetime disability worldwide. Although depression is a multifactorial disorder, the relative deficiencies in omega-3 EFAs may intensity vulnerability to it. Researchers are beginning to suspect that a decrease in the intake of omega-3 EFAs may adversely affect the nervous system and increase susceptibility to depression. Because 60% of the brain is fat and DHA is the most abundant fat in the brain, low levels of DHA can result in alterations of neuronal membranes that, in turn, cause changes in brain function. Another area of concern is determining the circumstances in which the brain can become depleted of DHA.

It is known that when the body is starved, the brain tends to conserve its store of DHA. However, chronic alcohol abuse has been shown to decrease the brain’s DHA stores, and alcoholism is associated with increased depression and violence. The connection between low DHA levels and brain neurochemistry that predisposes people to specific emotional disorders may lie in the relationship of brain DHA to brain serotonin levels. Low levels of serotonin have been documented in people who suffer from depression or are violent or suicidal. Rats fed a diet deficient in omega-3 fatty acids have a compensatory increase in serotonin receptor density similar to that seen in the frontal cortex of human suicide victims.

Attention-Deficit/Hyperactivity Disorder

Approximately 2 million children, or 3-5% of the school-age population, have a diagnosis of ADHD, making it one of the most common pediatric psychiatric disorders in this country. Children with ADHD exhibit a variety of symptoms from impulsive behavior to hyperactivity and are liable to experience problems at school and at home.

DHA deficiencies may play a role in the development of such difficulties. A comparative study of 96 boys53 with ADHD and 43 controlsfound that subjects with ADHD had significantly lower levels of highly unsaturated fatty acids, including DHA. The incidence and severity of a variety of symptoms of EFA deficiency were documented and compared with the fatty acid concentrations in the subjects’ plasma phospholipids and RBCs. A higher percentage of children with ADHD had symptoms of EFA deficiency and lower EFA concentrations than did controls. Also, a much higher proportion of boys in the ADHD group had been fed formula as infants.

Markers of EFA Deficiency In Boys With and Without ADHD

Reproduced with permission from Patient Care and copyrighted by Medical Economics. 9/00

*This article was written in 2000. Since then, DHA has been added to many infant formulas in the U.S.