"To avoid side effects like altering taste and low levels of toxins, or if you are vegan or allergic to fish, you can take fish-free omega-3 supplements made from algae (which is where the fish get it from!) The cheapest and highest dosage...
If you don’t eat fish—the main food source of the omega-3s DHA and EPA—at least two to three times a week, you might consider a supplement (or fortified foods), says Joe Hibbeln, M.D., Acting Chief, Section on Nutritional Neurosciences at the National Institute on Alcohol Abuse and Alcoholism. Here’s help.
Go for DHA+EPA. Studies suggest that this combination of omega-3s is best for overall health (e.g., preventing heart disease and depression, promoting healthy brain development). A third type of omega-3 fat, alpha-linolenic acid (ALA), found in flax, is not very effective at promoting overall health.
Take 900 mg to 2,000 mg/day if you’re an adult eating about 2,000 calories a day; 400-500 mg/day is a good target for kids who eat about 1,000 calories/day, suggests Hibbeln. If you limit omega-6 fats in your diet, you can consume less, he says.
Get the facts on toxins. Generally, omega-3 supplements are very low in toxins we associate with some fish. None of the 52 omega-3 products tested by independent group ConsumerLab.com in 2008 had detectable levels of mercury. Earlier this year, a lawsuit was filed by a group that tested 10 fish-oil supplements and found them all to be in violation of California’s Prop 65 law (which requires labeling carcinogens, at any exposure level) because they contained PCBs. “This [lawsuit] was a labeling issue, not a safety issue, but was helpful in raising awareness of contamination and identifying producers with higher levels,” says Tod Cooperman, M.D., president of ConsumerLab.com. Seven of the 10 supplements in the suit had total daily PCB levels under 100 nanograms; none exceeded 900 nanograms. (The Environmental Protection Agency estimates most adults can consume up to 1,400 nanograms/day without harmful effects.) Many of the supplements in this suit were made from larger fish, which accumulate more toxins.
“The health risks of [omega-3] deficiencies are much greater than the minimal increase in health risk from exposure to the low levels of PCBs and methylmercury,” says Hibbeln. Minimize exposure by choosing supplements made from smaller fish, such as sardines, or algae and brands that rated well in independent testing: fishoilsafety.com or ConsumerLab.com.
(Note: It’s best to consult your doctor before taking any supplement.)