The claims of late for fish oil sound as extravagant as those for snake oil-but a closer look at the research suggests that fish oil may actually live up to its amazing promises. The secret ingredient? Two special omega-3 fats-called EPA and DHA-that are found in every fish, but which are lacking in almost everyone's diet.

There's real evidence that inside the body, fish oil omega-3 fats help prevent or treat rheumatoid arthritis, asthma, heart attacks, cancer, Crohn's disease, attention deficit disorder, schizophrenia, manic depression, cystic fibrosis, and severe menstrual cramps. Some experts even tie the rise of depression in the twentieth century to diets low in omega-3s.

Fish Oil, Natural Fish Oil. The Evidence

The most convincing evidence for fish oil suggests that it helps prevent fatal heart attacks. Fish oil helps keep the heart from beating irregularly, which may explain why a recent Italian study of 11,000 heart attack survivors found that those who took 1,000 milligrams (mg) of fish oil omega-3s per day had 45% fewer fatal heart attacks over the next 3 1/2 years.

One of the newest and most promising areas of research is the complementary use of fish oil in treating depression, bipolar disorder, and schizophrenia. Omega-3 researcher and psychiatrist Andrew Stoll, MD, of Harvard Medical School, recommends fish oil supplements along with prescription medications to many of his own patients with depression and bipolar disorder.

Caution: fish oil side effects (usually at higher doses) may include heartburn and bad breath; taking the supplement with meals helps minimize these. Fish oil should not be used if you have uncontrolled hypertension or bleeding disorders, or if you take prescription blood-thinning medication.