We hear plenty about the health benefits of omega-3s—and for good reason. More than 23,000 medical or scientific articles have been published on them, and nearly 3,000 articles have focused on their effect on people.

“As dietary fats go, the omega-3s are without question the healthiest, and they have no negatives,” says Ron Hunninghake, MD, chief medical officer of the nonprofit Riordan Clinic in Wichita, Kansas. “They have so many benefits to body and mind, and yet most people don’t get enough of them.”

The term omega-3 refers to the fats’ chemical structure, and the principal dietary omega-3s are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Most supplements contain both, but in varying ratios. There’s also growing interest in DPA (docosapentaenoic acid), which is found in fish oil supplements but not usually listed on the label.

Although the term omega-3 is practically synonymous with fish oils, vegetarian sources of DHA and EPA are also available, but at lower doses.

Healthy hearts

Omega-3 fish oils are mild blood thinners and reduce the risk of erratic heartbeats called arrhythmias. Some research has shown that they can slow the heart rate and improve blood vessel flexibility. A new study, published in the Journal of the American Medical Association, looked at more than 45,000 people. The key finding: High blood levels of fish-source EPA and DHA lowered the risk of fatal heart attack by 20 to 22 percent. The researchers noted that high DHA and DPA seemed to have the greatest benefits.

Dose: 1 to 2 grams omega-3s daily*

Quelling inflammation

Inflammation underlies arthritis, gingivitis, allergic rhinitis and other “-itis” diseases. Luckily, EPA and DHA are the building blocks of three powerful anti-inflammatory compounds, namely prostaglandin E3, resolvins and protectins. Diets high in grain-sourced cooking oils, such as corn oil, suppress EPA and DHA, but taking omega-3s restores a balance and reduces inflammation.

A new study suggests that DHA may have slightly stronger anti-inflammatory effects when compared with EPA, but it’s important to take both.

Dose: 2 to 4 grams omega-3s daily*

Dry eyes

Not just a condition of seniors, dry eyes can affect computer users and people who wear contact lenses. Symptoms include stinging, a lack of tears to maintain a moist surface on the eyes, blurred vision and damage to the eyes. Several recent studies have found that dry eyes reflect an omega-3 deficiency, which can be corrected by taking supplements.

Dose: 1 to 2.4 grams omega-3s daily*

Better moods

Omega-3s are essential for normal brain development in utero and early in life, but we need them throughout life, too. Natalie Parletta, PhD, of the University of South Australia, says they help “oil the brain.” Japanese researchers just reported that high levels of omega-3s, particularly DHA, can reduce the risk of depression by up to 45 percent. Numerous studies have also found omega-3s valuable in treating severe depression, post–traumatic stress disorder, anxiety, bipolar disorder, impulse control and hyperactivity.

Dose: 1 to 10 grams omega-3s daily,* depending on the severity of the mood disorder. Both EPA and DHA are effective.

Staying sharp

Omega-3s can slow age-related cognitive decline. A study by Chicago researchers found that high omega-3 intake slowed mental decline in seniors, especially those with a gene that boosts the risk of Alzheimer’s disease. A study at the University of South Dakota found that women with high blood levels of EPA and DHA had larger brain sizes and less age-related brain shrinkage.

Dose: 0.5 to 1.5 grams omega-3s daily*

*1 gram = 1,000 milligrams