A Whopper of a Tale

Omega-3s, found mainly in fish, might be the key to suppressing depressive symptoms in adults.

By Hara Estroff Marano, published July 1, 2003 - last reviewed on June 9, 2016

It's hailed as the most important finding in psychiatry in the last 40 years. Yet the information is as old as mankind.

Compelling evidence is amassing that regularly eating a class of fats widely found in fish and seafood is effective in preventing and even treating depression. The fats, so-called omega-3 fatty acids, turn out to be critical components of nerve cells and are available solely from what we eat.

Omega-3 fats also appear to have been integral parts of the diets of our prehistoric ancestors. Although the amount of omega-3s in the food supply has radically dropped in the past hundred years, eons of evolution have custom-crafted our brains and bodies to depend on them for basic biochemical maneuvers.

It's taking some very sophisticated science to highlight just what functions omega-3s serve for modern man. Ongoing research indicates that they are key to the smooth operation of arteries and hearts, and abet blood flow. A lack of omega-3s may help explain why depression and heart disease tend to occur together. Omega-3s also keep the immune system from overreacting.

But their most significant role may be in the brain. There are two principal omega-3s, DHA, or docosahexaenoic acid, and EPA, or eicosapentaenoic acid, and scientists now know that DHA spurs the development of the infant brain and visual system. In fact, the Food and Drug Administration has approved DHA for incorporation into infant formulas in the U.S.

Joseph R. Hibbeln, M.D., a psychiatrist at the National Institute of Alcohol Abuse and Alcoholism, almost single-handedly opened the most exciting frontier in medicine in the mid-1990s when he reported that prevalence rates of major depression around the world vary as much as 50-fold, and the differences can be predicted by a single factor—a country's rate of seafood consumption. Since then, researchers have shown that:

  • In a double-blind pilot study of 30 patients with manic-depression who had not responded well to standard medications, omega-3s (given as fish-oil capsules) stabilized mood so effectively the trial was halted after four months so that more patients could be treated with the supplements, alone or in combination with drugs. A larger study is now underway.
  • One gram a day of EPA given to patients with major depression improved their clinical course by 50 percent over and above that achieved by the antidepressants they were already taking.
  • Blood tests of depressed patients show a marked depletion of omega-3s in red blood cells.
  • Prevalence rates of seasonal affective disorder follow latitude—except for Iceland and Japan, two northerly countries where fish is consumed regularly.
  • In a survey of 3,000 people of northern Finland, eating fish two times a week reduced by 47 percent the risk of being depressed, and similarly reduced suicidal thinking.
  • In a stringently controlled study of 22 countries, prevalence rates of postpartum depression were found to vary according to rates of seafood consumption. "Pregnancy depletes mothers of omega-3s," explains Hibbeln. "The placenta selectively binds DHA and delivers it to baby's brain." The U.S. fared poorly in the survey, particularly the inner cities.
  • In a strictly controlled 16-country analysis of prevalence rates for several psychiatric disorders, schizophrenia and anxiety disorders showed no relationship to seafood consumption; but a 30-fold variation in rates of bipolar disorder could be predicted by amount of seafood consumed.
  • In newborn animals fed DHA-supplemented formula, levels of the neurotransmitter serotonin doubled in the frontal cortex, an area of the brain implicated in mood disorders.

No one is sure yet whether the effective antidepressive agent in adults is EPA or DHA or both. Or how much of either, in what proportion, is needed. And it's not clear when the most important effect of omega-3s against depression is established.

"In the cross-national surveys, the people have been exposed to differing intake of omega-3s virtually their entire life. The data does not say whether the protective effect was established primarily in early development and carried into adulthood, or whether there's a direct treatment effect in adulthood. Data suggests the latter, but that does not rule out an impact also in infancy."

The story of omega-3s in medicine, says Hibbeln, "is just getting underway." He and others believe that across the board, Americans should increase their intake of omega-3s. But given the unknowns, he is content to recommend getting the fatty acids from real food rather than supplements.

Both EPA and DHA are found in algae and seaweed and travel up the food chain to all seafood. It is a myth, says Hibbeln, that they exist only in cold-water fish. The highest concentrations of DHA are found in caviar and mackerel. Sardines are close to the top. Omega-3s are also found in flaxseed, walnuts, wild plants and game.

Hibbeln's recommendation for preventing psychiatric disorders is exactly what the American Heart Association now believes fights cardiovascular disease—eating seafood two to three times a week. That includes crabs and shrimp and oysters. "They're all better than hamburger," he says.

But adding seafood is only half the story. It's essential to cut out sources of corn oil and soy oil—almost ubiquitous in margarine, fried foods and commercial salad dressings. They contain a predominance of omega-6 fatty acids, which compete in the body with omega-3s and displace them.

"If you cut out soy oil and corn oil, and use olive oil instead, you will double the effect of any fish that you eat," Hibbeln contends. "You get closer to a Mediterranean diet. And that's closer to the diet on which mankind evolved."

Nevertheless, high concentrations of fish oils in supplements are available in health-food stores. But anyone who takes fish oil supplements has to also take antioxidant vitamins to prevent the conversion of omega-3s into substances that actually damage cell membranes. Andrew L. Stoll, M.D, head of psychopharmacology at Harvard's McLean Hospital and a key omega-3 researcher, recommends 500 mg of vitamin C and 400 units of E.

"I don't want patients to stop their medications and start these. It's best to work with your doctor. Educate your doctor," says Stoll.