Fights Depression:
Skimping on fish may depress you. Norman Salem Jr., a researcher at the National Institutes of Health, notes that populations consuming large amounts of fish have low rates of major depression. A lack of fish oil is linked to depression in alcoholics, people with multiple sclerosis and women with postpartum depression. Further, he says, some dieters who reduce overall fat, including fish fat, tend to get depressed.

A recent Australian study of 21 depressed patients confirmed that the most severely depressed had imbalances of fatty acids in their blood and cell membranes. Evidence suggests DHA-type fish oil helps regulate serotonin, a neurotransmitter known for its "feel-good" qualities. Depressed people often have low levels of serotonin.

Reduces Aggression:
You are less likely to express stress-induced aggression if your brain is under the influence of fish oil, according to Japanese researchers. In a new double-blind test of 41 adult students, those taking 1.5 to 1.8 daily grams of DHA fish oil for three months did not become more socially aggressive at a time of severe mental stress: final exams. In contrast, students taking a dummy look-alike capsule showed significant jumps in social aggression, as measured by psychological tests. This effect on stress may help explain how fish oil prevents heart disease. Stress hormones triggered by hostility and anger can constrict arteries and accelerate the formation of blockages, research shows; fish oil may suppress the release of those hormones.

Stimulates young minds: Fetuses and infants must get sufficient omega-3 oils for optimal brain development, says William Connor, Oregon Health Sciences University. In one telling study of premature infants, those fed breast milk had 8 points higher IQ at age 8 than those fed standard infant formula. Connor credits breast milk's higher amounts of DHA for that superior intelligence. In infant rhesus monkeys deprived of omega-3-type oils, Connor found severely impaired visual acuity and behavior indicative of a neurological defect. Autopsies revealed abnormalities in brain cells. Connor advises pregnant women to eat fish a couple of times a week, especially during the last trimester, the time of greatest fetal brain growth. And breast-feeding is preferable to infant formula, he says.

Blunts Brain Damage?
Fish oil may eventually be proved to lessen alcohol-induced brain damage, Salem says. He explains that excessive alcohol depletes brain levels of omega-3's -- DHA in particular -- which leads to neurological damage and impaired vision. He put experimental animals on high-alcohol, low omega-3 diets for six months to three years. They suffered severe losses of DHA in brain cells and detrimental changes in brain functioning. Some scientists speculate that fish oil also may have a protective role in degenerative brain diseases leading to memory loss and dementia. The brains of deceased Alzheimer's sufferers, for example, show low levels of omega-3 fats.

Influences Behavior:
Children deficient in omega-3 oils may be more likely to have behavioral and learning problems known as attention deficit hyperactivity disorder or ADHD, according to new research at Purdue University. John R. Burgess, assistant professor of foods and nutrition, tested the omega-3 blood levels of 96 boys, ages 6-12; about half had been identified as having ADHD. Clearly, Burgess says, "boys with lower levels of the omega-3 fat scored higher in frequency of behavioral problems," such as hyperactivity, impulsivity, anxiety, temper tantrums and sleep problems.

The big question:
Does taking more omega-3 and other appropriate fats cure the deficiency and improve ADHD behavior? That's what Burgess is trying to find out in a follow-up study. He cautions that only 40 percent of kids with ADHD in his study had low omega-3, so obviously it wouldn't work in most cases. Burgess also says it's unclear how much of what type of oils each individual child may need. Whatever you do, he advises working with health professionals and not stopping other treatments or medications for ADHD without proper medical advice.

Smart tips:
Restrict omega-6 oils (corn oil, regular safflower and sunflower seed oils, and most margarines), which tend to negate the benefits of omega-3. Recommended: canola and olive oils.

WARNING:
Pregnant women should avoid freshwater sports fish, which may be contaminated with environmental chemicals. One of the safest and best for everybody: sardines.

Jean Carper's current best-selling book is Stop Aging Now!