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posted: 7/15/2013 5:00 AM

Fish oil in diet may affect depression symptoms

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How much fish oil in the diet is needed to reduce the symptoms of major depression?

In a recent medical study, increasing dietary consumption of docosahexanoic acid significantly improved symptoms of major depression. In addition, the quantity of DHA in the cell membranes of red blood cells correlated strongly with reduction in depression symptoms.

Major depression is believed to be related to changes in how the brain functions. This condition is characterized by low self-esteem, severe loss of interest in activities, extreme fatigue and profound depression.

There are many theories as to what is the cause of depression. Some suggest that depression is primarily psychologically based in personality and genetics. Biologically based theories propose that changes in levels of certain neurotransmitters, such as serotonin, dopamine and norepinephrine, are the causes of major depression.

While the cause of depression is unknown, it is relatively common worldwide, affecting more than 300 million people. Interestingly, the United States has the highest incidence of major depression and Japan has the lowest incidence.

In the U.S., major depression is more common between the ages of 30 and 50. Chronic illness is a risk factor for major depression. Unfortunately, neither psychotherapy nor medications are universally effective in treating major depression.

There are numerous studies to indicate that increasing consumption of specific fish oils, especially DHA, can reduce the symptoms of major depression. DHA belongs to a family of fats called omega-3 fatty acids. We are able to synthesize DHA from other compounds, we just don't do it very efficiently and must supplement it in our diet.

DHA is very important for nerve function. It is the most common omega-3 fat found in the brain and eye retinas. DHA comprises up to 40 percent of brain cell membranes. This fatty acid is essential for good brain function. In general, most Americans do not get enough of it in their diet.

Although there are many clinical studies demonstrating that DHA supplementation can reduce depression symptoms, quantification is lacking in how much DHA in cell membranes is needed.

In a recent medical study at the University of Wollongong, Australia, correlated the concentration of DHA in the cell membranes of red blood cells with reduction in symptoms of depression. In the study, 95 participants with major depression were randomized to receive either DHA or olive oil (placebo).

During a 16-week period, DHA increased in the red blood cell membranes in both groups. However, DHA comprised 16 percent of the fatty acids in the red blood cell membrane in the fish oil group and only 8 percent in the olive oil group. Improvements in depression were significantly greater in the fish oil group.

Although more studies are needed, this particular clinical trial was important because it correlated the level of DHA in red blood cells with changes in depression. Measuring red blood cell DHA may become an essential clinical tool for determining the optimal amount of dietary fish oil.

Patrick B. Massey, M.D., Ph.D, is medical director for complementary and alternative medicine for the Alexian Brothers Health System. His website is

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