Eating fish may help pregnant women avoid depression

SAN FRANCISCO — Pregnant women might be able to lower their risk of becoming depressed before or after giving birth by eating fish, a study suggests.

That is because they will get a nutrient called omega-3 fatty acids, which are found in seafood and are also available in fish oil supplements, researchers say.

Oily fish such as salmon, tuna, sardines and herring are especially rich in omega-3. These particular fish are not on the federal list of fish pregnant women should avoid because of high levels of mercury.

In an analysis of 11,721 British women, researchers found that the more omega-3 fatty acids a woman consumed in seafood during the third trimester, the less likely she was to show signs of major depression at that time and up to eight months after the birth.

In fact, the rate of depression in the women with the highest intakes was only about half that of women with the lowest intakes, said one of the researchers, psychiatrist Dr. Joseph R. Hibbeln. Eating fish two or three times a week was typical of the highest-intake group, Hibbeln said.

The federal government says that because of mercury contamination, pregnant women should limit themselves to an average of 12 ounces a week of a variety of fish, an amount Hibbeln said corresponds to about two servings. He also said that federal data show very little mercury in salmon, catfish, scallops and tilapia, and that fish-oil supplements are supposed to be free of mercury.

As for why would omega-3 fatty acids reduce the risk of depression, Hibbeln said they are key building blocks of the brain, and studies show that low levels in the diet are associated with low levels of a brain chemical called serotonin. Low levels of serotonin, in turn, are implicated in depression.

About 10 percent of pregnant women develop depression severe enough to interfere with their functioning, and the figure jumps to 13 percent to 15 percent in new mothers.

Pregnant women could be particularly vulnerable to low levels of omega-3 fatty acids because the developing fetus draws on supplies stored in the mother's body, Hibbeln said. "If mothers don't eat enough, they're likely to become depleted," he said.

In the depression study, the results held up even after researchers accounted for other factors that influence risk of the illness.

Still, more definitive studies should be done before omega-3 fatty acids are recommended to pregnant women for avoiding or easing depression, said Hibbeln, chief of the outpatient clinic at the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Md.