The Importance of DHA in Adult Health

DHA is important for ongoing brain, eye and heart health. It is also important for brain, eye and heart function throughout life. Throughout our lifecycle, the body will continue to turnover DHA and it is important to replenish the stores of DHA in our bodies. While the body can convert DHA from its precursor fatty acids, this process is inefficient. It is therefore important for adults to obtain adequate amounts of DHA in their diets.

Brain and Eye Health

DHA is the predominant omega-3 fatty acid in the brain and eyes and is necessary for the optimal structure and function of nerve cells in the brain and eyes. In the brain, DHA is especially concentrated in the region responsible for complex thinking skills.

  • A scientific review on DHA stressed the significant role that DHA plays in the maintenance of normal neurological function.
  • Low levels of DHA observed in the elderly may contribute to or accompany the onset of symptoms associated with age-related mental decline.
  • An agency within the U.S. Department of Health and Human Services, the Agency for Healthcare Research and Quality (AHRQ), has evaluated the effects of omega-3 fatty acids on cognitive function and identified three studies investigating the relationship between the consumption of omega-3 fatty acids found in fish and dementia. AHRQ notes "[f]ish consumption was associated with a reduced risk of Alzheimer's dementia in all three of the studies but this association was significant in only one study."
  • AHRQ also observes “[t]otal omega-3 FA consumption and consumption of DHA (but not alpha-linolenic acid, ALA, or eicosapentaenoic acid, EPA) were associated with a significant reduction in the incidence of Alzheimer's." AHRQ concludes "[a]dditional research on the effects of omega 3 fatty acids needs to be performed on all of the conditions reviewed in this report before recommendations regarding the use of omega-3 fatty acids can be made for these conditions." A copy of the AHRQ summary report is available on the agency’s website.
  • There is preliminary research exploring the possible role of DHA in neurological function. Promising results from animal model and human-cell model studies suggest DHA may play a role in reducing the risk of certain neurological diseases. Additional research in humans is needed to evaluate the effect of DHA supplementation on preventing or treating these neurological disorders. Further research is also needed to determine the exact mechanism of action.
  • A Japanese animal-model study found that DHA supplementation reduced the increase in number of reference and working memory errors and increased the antioxidative defenses suggesting DHA as a possible agent for ameliorating learning deficiencies due to Alzheimer’s.
  • The results of a human-cell model study showed that DHA intake may lower the accumulation of a protein that is associated with brain aging and Alzheimer’s disease.
  • An animal-model study showed that DHA may protect against the accumulation of a protein believed to be linked to Alzheimer’s disease.
  • An animal-cell model study noted that DHA enrichment likely induced changes in neuronal membrane properties, which may assist in the prevention of Alzheimer’s disease and other neurological diseases.
  • One study reported that a high intake of DHA decreased the risk of developing age-related macular degeneration, a major cause of blindness.
  • One study reported there is a strong correlation between low DHA levels in retinopathy patients and the severity of their disease.
  • One study showed that those who suffer from LCHADD (long-chain 3 hydroxyacyl-CoA dehydrogenase deficiency), a rare genetic disorder with progressive vision loss, experienced improved or stabilized vision after receiving DHA supplementation. Observations have suggested a role for DHA in other visual conditions; however, additional research is needed.
Cardioprotective Effects of DHA

DHA is also a key component of the cardiovascular system. In the past 25 years, there have been over 4,500 studies of the cardiovascular effects of long-chain omega-3 polyunsaturated fatty acids, such as DHA.

  • Although the exact relationship between DHA and the cardiovascular system is still being studied, observational and intervention studies support an association between DHA and good cardiovascular health.
  • Based on the current body of research, several scientific bodies have made recommendations regarding the intake of omega-3 fatty acids and good cardiovascular health.
  • Despite the recommendations, the typical American’s daily DHA consumption is still low. A dietary study of 9,323 U.S. adults revealed that the average intake of DHA was 61 mg/day for women and 78 mg/day for men.
Controlling Blood Lipids
  • Controlling blood lipids (total cholesterol, low density lipoprotein (LDL or “bad” cholesterol), high density lipoprotein (HDL or “good” cholesterol)) and triglycerides is important for reducing the risk of developing heart disease.
  • One of the cardioprotective effects of DHA appears to be helping to normalize certain blood lipids. Three independent research studies in subjects with normal blood lipids have demonstrated a statistically significant drop (14-26 percent) in triglycerides and a trend toward higher HDL levels over baseline lipid levels after supplementation with high doses of DHA (more than 1.5g DHA/day) for 2-15 weeks. A fourth study showed similar blood lipid changes in the DHA group compared to the placebo group.
  • In two double-blind, placebo-controlled trials of subjects with abnormal lipids, supplementation with more than 1.2g DHA/day for 6 weeks resulted in a clinically significant drop of approximately 20 percent in triglycerides and a statistically significant increase in HDL or HDL2 levels. These changes in blood lipids were accompanied by minimal or insignificant increases in total cholesterol and LDL.
Controlling Blood Pressure
  • Controlling blood pressure is also important for maintaining cardiovascular health. One study found that DHA had modest blood pressure lowering effects in mildly hyperlipidemic men.