So how many omega-3 fatty acids are enough — and how should you get them? That likely depends on your age and your specific health concerns.
The United States does not yet have guidelines for DHA or EPA, and consensus among nutrition experts is elusive. But specialty groups, some governmental agencies and individual experts have started to take a stand.
For healthy adults without major medical issues, the European Food Safety Agency recommends a daily dose of 250 milligrams of combined EPA and DHA, while the National Heart Foundation of Australia suggests 500 milligrams. A NATO workshop recommended 800 milligrams per day. EPA and DHA are often taken, and measured, together.
People with heart disease, according to the American Heart Assn., should get 1 gram of EPA and DHA a day. People with high triglycerides should take 2 to 4 grams under a doctor's supervision.
Pregnant and breast-feeding women should focus on DHA, aiming for at least 200 to 300 milligrams a day, according to several expert groups. If they don't eat fish, women should take fish oil pills or supplements that have a 3-to-1 ratio of DHA to EPA, says nutritional scientist Bruce Holub of the University of Guelph in Ontario and executive director of the DHA/EPA Omega-3 Institute there. That's the same ratio found naturally in fish, he says, and getting too much EPA compared to DHA during pregnancy might diminish DHA's benefits.
Kids, says Philip Calder, a nutritionist and omega-3 researcher at the University of Southampton in England, should probably get between 100 milligrams and 250 milligrams a day.
Very few Americans reach those recommended amounts. One study found that the average pregnant woman in Canada consumed just 80 milligrams of EPA and DHA a day. Another study, which looked at everything a group of Canadian children ate over the course of a week, found that an average 2-year-old got just 19 milligrams per day, with half getting less than that. Four- to 8-year-olds did only slightly better with 55 milligrams per day. The average American adult, according to other research, gets 120 milligrams to 150 milligrams daily.
In extremely large doses, omega-3s can increase the amount of time it takes for blood to clot — a potential danger for people taking blood-thinners or those with clotting problems. Otherwise, it's hard to reach an upper limit, Calder says. People in arthritis studies take 3.5 grams of omega-3s, or nine standard fish oil pills, every day for up to a year without any problems.
"I think it is really difficult to overdose on omega-3 fatty acids," Calder says.
Foods or pills
Eating fish is an easy way to stock up. Fatty and oily fish such as salmon and mackerel score higher than lean fish, like cod or tilapia. Even within a single variety of fish, though, levels can vary widely, based on what the fish ate while it was alive.
A 100-gram serving of salmon, for example, may contain 400 milligrams to more than a gram of DHA, and from less than 200 milligrams of EPA to more than 800 milligrams.
To be sure of what you're getting, especially if you're not a big fish-eater, it might be easiest to go for fish oil pills, supplements or fortified foods. Supermarkets now carry eggs, yogurt, milk, juice, margarine, bread and other foods boosted with omega-3s.
Calder suggests avoiding products enriched with ALA. It's also not worth spending money on supplements that tout omega-6 or omega-9 fatty acids, he says, which many Americans may already get too much of.
With fish oil pills, look for varieties that are as concentrated as possible. Most are made from anchovies and other small fish that don't spend long in the ocean, but if you're worried about mercury or other contaminants, the Environmental Defense Fund offers a guide to brands online. Vegetarians can get the same benefits from algae-based supplements, which are also the kind that appear in some infant formulas.
For babies who aren't breast-feeding, doctors recommend formula fortified with DHA — as many studies show benefit and none show harm.
Whatever your age or ethical beliefs, the bottom line is that you should get omega-3s however you can.
"Everybody needs these fatty acids," Calder says. "This holds for boys, for girls, for men and for women. That's everyone in the population who can eat for themselves."