Fish oil supplements are pretty safe
One of the concerns about eating lots of fish or fish oil is the possibility that you will consume harmful PCBs and methyl mercury. The experts note that a Consumer Reports survey of store-bought fish oil supplements found them to be safe in that regard. But beware of overdosing. Three grams or more per day of EPA and DHA may cause excessive bleeding in certain people. The Food and Drug Administration has approved a medicine, Lovaza, which can deliver higher doses of EPA and DHA—but only with a doctor's prescription. Turned off by "fish burp"? Though not dangerous, this side effect is a problem for some consumers of fish oil supplements. Kopecky suggests avoiding the issue by chilling the pills in the freezer before taking them.
Algae supplements and plant sources might not be ideal—unless you combine them
According to Kopecky, algae-derived omega-3 supplements are produced through a fermentation process that generates DHA but not EPA. And when people get their omega-3s from ALA-rich plant sources like flax or walnuts, he says, "the body converts ALA into primarily EPA and only a little bit of DHA." In either case, the consumer may not get an ideal ratio of EPA and DHA. To reap the full cardiovascular benefits of omega-3s, one could theoretically combine algae for its DHA boost with plant foods for their ALA-to-EPA boost, he says. The bottom line
So, should you go for fish or load up on plant-derived sources for optimal omega-3 intake? "Given incomplete evidence, I think it is good for most people to aim for some of both," says Willett. Aim for at least two servings of fatty fish per week for EPA and DHA and a daily helping of ALA from a plant source. (Again, consider these 11 foods rich in omega-3s.) If you don't eat fish, though, don't worry. "Certainly, we know there are large populations that eat no fish, and they seem to be fine as long as ALA intake is adequate," he says. Vegetarians with risk factors for heart disease might consider taking an algae supplement for full omega-3 coverage, he adds. As Kopecky notes, those with heart disease or its risk factors might benefit from a DHA-EPA supplement. Omega-3s aren't the only essential fatty acids in our diet. Omega-6s are important for blood clotting and fighting infections. U.S. News has also written about the right way to get omega-6—and the dangers some experts see in getting too much.