People with bipolar disorder have lower levels of certain omega-3 fatty acids that cross the blood-brain barrier compared to those who do not, according to researchers from Penn State College of Medicine and the National Institutes of Health. The finding could have implications for dietary interventions for the disorder.
Bipolar disorder is a brain disorder that causes manic episodes of elevated mood, energy and cognition, and major depressive episodes of lowered mood, energy and cognition.
Fatty acids are a major area of interest in bipolar disorder and depression because of their biological importance in the brain. Studies have shown that fatty acid supplementation may be useful for unipolar depression, but the data has been more mixed for bipolar disorder.
The researchers compared fatty acids in 27 people with symptomatic bipolar disorder and 31 healthy control subjects. The group measured levels of different forms of the polyunsaturated fatty acids omega-3 and omega-6. They also collected self-reported information on fatty acid consumption and bipolar medication use.
Free fatty acids are able to cross the blood-brain barrier, while fatty acids bound to proteins are not. In study subjects with bipolar disorder, the ratio of a free-circulating omega-3 fatty acid called EPA to bound EPA was lower than in other people, meaning that the availability of omega-3 in the body is lower in bipolar subjects.
Omega-3 fatty acids are a large component of brain-cell membranes and are important for cell-to-cell communication in the brain. In the study, the ratio of free to bound EPA correlated with clinical bipolar symptoms, specifically mania and tendency towards suicide.
Fatty acids also play an important role in the immune system and the inflammatory system.
Omega-3 and omega-6 fatty acids can shift the balance of inflammation, which researchers think is important in bipolar disorder.
However, the researchers did not find altered ratios of omega-3 to omega-6 fatty acids in bipolar subjects.
Although the researchers did find lower levels of omega-3s in patients with bipolar disorder that correlated with symptoms, they say it's too early to advise dietary changes or omega-3 supplementation.
Omega-3 fatty acids are abundant in fish, vegetable oils, nuts -- especially walnuts, flax seeds, chia seeds and flaxseed oil.
There was no difference in self-reported fatty acid consumption between bipolar and healthy patients.
It is possible people couldn't accurately recall what they were eating.
Another possibility is that there are differences in how healthy people and people with bipolar disorder convert fatty acids from one form to another. Drugs that treat bipolar disorder are known to affect these conversions, but no association was found between fatty acid levels or ratios and self-reported medication use in the study.
The researchers are currently investigating if modifications in dietary intake of fatty acids could be useful in bipolar disorder.
A number of trials have turned up no benefit of omega-3 supplementation in bipolar disorder.
Most research on fatty acids in bipolar disorder measures levels of fatty acids in cell membranes. This new study looked at circulating fatty acids in the blood, which is a better indication of dietary intake. Fatty acids in the blood are also the type that crosses the blood-brain barrier to enter the brain.
Source: Bipolar Disorders, online October 1, 2015.
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