Fish oils that are already believed to reduce the risk of heart disease may help combat a number of serious psychiatric illnesses as well, researchers said yesterday.
At an international conference sponsored by the National Institutes of Health, scientists said that though the data are preliminary, a growing body of evidence suggests that higher consumption of essential fatty acids in the oils, notably one called omega-3, appears linked to a lower risk of depression and better treatment of manic-depression and schizophrenia.
Essential fatty acids must be consumed in the diet or as supplements because the body cannot make them. A major dietary source of omega-3 is fatty fish such as mackerel, Atlantic salmon, bluefish, halibut, herring, and sockeye salmon.
The researchers did not make specific recommendations for consuming fish or omega-3 supplements. But previous research suggested that eating fish two to three times a week is healthful, says Larry Lindner, executive editor of the Tufts University Health & Nutrition Letter.
People seeking to increase their consumption of omega-3 fatty acids also can eat green leafy vegetables, nuts, flaxseed, and canola oils, which contain fatty acids that the body can make into two chemicals, called EPA and DHA, that are thought to produce the health benefits. The researchers said they had no definitive answers on whether DHA, which is found in breast milk, should be added to infant formula in America, as it is in Europe and Asia.
Consuming high quantities of omega-3 supplements, however, can suppress immune function, conceivably leaving people more vulnerable to infection. On the other hand, Lindner said, omega-3 supplements seem to help people with arthritis, an auto-immune disorder. A 3,000-milligram daily dose has been shown to reduce arthritis symptoms caused by immune system damage to joint tissue. Omega-3 also can reduce the ability of the blood to clot, which means it could be hazardous in a person with a bleeding disorder.
The research includes data suggesting that countries where large quantities of fish are eaten have lower rates of depression than countries where fish is not a major part of the diet, said Dr. Joseph R. Hibbeln, chief of the outpatient clinic at the National Institute on Alcohol Abuse and Alcoholism at the National Institutes of Health.
Major depression is 60 times more prevalent in some countries than others, Hibbeln said. Fish consumption appears to be an “important protective factor.”
Lindner called the link between fish oils and reduced incidence of depression “provocative,” but said it was “too early to make a recommendation that people suffering from a mood disorder should eat more fish or start taking omega-3 supplements.”
Hibbeln’s team found that higher blood levels of two omega-3 fatty acids (EPA and DHA) in both normal people and alcoholics correlated with higher levels of an important brain chemical, serotonin. This suggests, he said, that consuming omega-3 fatty acids may influence production of serotonin. Many scientists believe that low levels of serotonin are linked to depressive, suicidal, or violent behavior.
In one study of 18 suicidal patients, higher blood levels of EPA were linked to lower scores on tests that predict suicide, Hibbeln noted. The emerging data, taken as a whole, suggest that EPA and DHA may reduce depressive and suicidal behavior.
Dr. Andrew L. Stoll, director of psychopharmacology at Brigham and Women’s Hospital in Boston, reported what he called “very exciting” results from a study of about 50 patients with manic-depression, or bipolar disorder, which affects an estimated 2 million Americans.
About half the patients were given 10 grams a day of omega-3 (equal to several servings of fish) in a special formulation and the other half received a placebo made of olive oil. All patients continued to receive their usual medications as well.
The study was planned to last nine months, said Stoll, but after four months the rate of relapse in the omega-3 group was dramatically lower, prompting researchers to stop the study early. Although it is not totally clear how omega-3 works, Stoll said, it appears to act like lithium and valproate, two manic-depression medications that block transmission of neurochemical signals inside brain cells.
Omega-3 fatty acids also appear to help reduce symptoms of schizophrenia in people taking standard medications, said Dr. Malcolm Peet, head of psychiatry at the University of Sheffield in the United Kingdom. Schizophrenia, which affects 1 percent of the population, produces delusions, hallucinations, apathy, and withdrawal.
Peet has found that levels of fatty acids are lower in people with schizophrenia. In three small studies, he said, giving omega-3 supplements to schizophrenic patients appears to lessen the severity of symptoms.