For people suffering from depression or bipolar disorder, prescription drugs can be a mixed blessing. Even if they help—and they don’t always—the side effects, including weight gain and depressed sex drive, can be disheartening. Now it appears as if fish oil—yep, that fish oil, available at your local health food store—may help control these ailments.

The positive impacts of fish oil on heart and skin health have been relatively well-publicized. Many of its other benefits are not as well-known, though. Studies suggest that fish oil can also prevent diabetes, protect against allergies and macular degeneration, and—the focus of this article—stabilize mood disorders.

The working ingredient in fish oil is omega-3, a polyunsaturated fatty acid. The active ingredients in Omega-3 fish oil are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Of these, EPA appears to be the key to stabilizing mental health.

Two important studies, one published in 1996 and the other in 2003, examined the relationship between bipolar disorder and seafood consumption in different countries. Both found a strong reverse correlation—the more seafood consumed, the less bipolar disorder. In Japan, for instance, where the average person consumes 150 pounds of seafood per year, the rate of depression is 60 times lower than it is in New Zealand, where seafood consumption is 40 pounds/year. And did you know that postpartum depression is 50 times higher in countries with low levels of seafood consumption?

Other researchers have conducted controlled studies, giving one group of patients fish oil, and another group a placebo. Here, too, the findings support the therapeutic value of omega-3. A 1999 Harvard study of the impact of fish oil on people with bipolar disease, which was supposed to go on for nine months, was stopped after four because the results were so positive. The study found that both manic and depressive episodes were significantly reduced in people taking fish oil. Other studies have found similar results for people suffering from “straight” depression.

If you decide to use fish oil to support your mental health, how much should you take, and in what form? Andrew Stoll, who conducted the Harvard study, recommends 1.5 to 3.5 grams of omega-3 a day, taken with food. Why not simply eat fish? Capsules or liquid may be better than a fish-rich diet because of the toxic loads in fish. This is because impurities are removed from “pure” fish oil by molecular distillation.

More is not necessarily better with omega-3. Some studies suggest that its beneficial effects are actually reduced with higher dosages, perhaps because taking high levels of omega-3 produces oxidative stress. For this reason, some doctors recommend taking anti-oxidants like vitamins C and E with your omega-3.

It’s also important to remember that “fish oil” is a bit of a misnomer. It’s really omega-3 fatty acids that you want, and they’re not a fish exclusive. Good news for vegetarians: Flaxseed oil can also provide your daily dose of omega-3.

Is omega-3 guaranteed to help against depression and bipolar disorder? The science hasn’t quite reached that point yet. The evidence strongly suggests that omega-3 can help, though, and since there’s no downside (except, for some people, the expense), there’s little reason not to give this natural solution a try.

Carl Frankel is a journalist and author who has been writing about green business, green products, and integral living for the past 20 years.