How To Pick Fish High in Omega-3 and Low in Mercury

Health experts have long recommended eating at least two servings of fish each week for heart health. That’s because fish contain essential omega-3 fatty acids, which are oh-so-important for keeping the cells all over your body running in tip-top shape. They also provide energy and support your heart healthy and hormonal system.

In short, omega-3s are really important to keeping your body healthy.

Fish are the go-to for loading up on those healthy omega-3s. But there are so many fish in the sea (not to mention the lakes, ponds, oceans and streams) and the health implications vary greatly from one kind of fish to the next.

Registered dietitian Julia Zumpano, RD, LD, offers help in navigating an ocean of fishy nutrition to find the best fish to include in your diet. Read on to learn about the fish that are highest in omega-3 and lower in mercury.

Benefits of eating fish

Omega-3 fatty acids are called essential fats because we need them to survive. The tricky thing is that our bodies can’t produce these types of acids on their own.

That’s where fish comes in.

“Fish is the No. 1 source of omega-3 fatty acids,” says Zumpano. “Fish provide two types of omega-3 fatty acids that our bodies need, called EPA and DHA.”

EPA stands for eicosapentaenoic acid and DHA stands for docosahexaenoic acid. Some plant-based foods provide the omega-3 fatty acid ALA (alpha-linolenic acid). More on those in a bit.

“Omega-3 improves cardiovascular health at a dosage between 1 and 4 grams each day,” Zumpano says. “It also lowers the risk of death for people with cardiovascular disease and abnormal heart rhythms.”

Omega-3 lowers their risk of death by:

• Reducing the risk of blood clots.
• Keeping plaque from forming in their arteries.
• Decreasing triglyceride levels in their blood.
• Slightly lowering blood pressure.
• Slowing production of substances that cause inflammation in the body.

Heart disease plays a role in how much fish you should eat, too. If you have no history of heart disease, eat at least 6 to 8 ounces a week, which is about two servings. The U.S. Food and Drug Administration (FDA) guidelines say healthy adults can eat up to 12 ounces of fish each week.

If you do have heart disease, stick to about 1 gram of omega-3 per day. Your doctor may even recommend supplements, but it varies on your condition, so be sure to consult your doctor about how much you should eat.

Beware of mercury

You may have heard about the risk of mercury poisoning from eating fish. Mercury poisoning can damage your brain, nervous system and other body systems.

The risks of mercury from fish vary depending on your age and your health. The American Heart Association says the benefits of eating fish outweigh the risks for most healthy adults.

“Some fish contain higher levels of mercury and environmental toxins,” Zumpano notes.

Your best bet for avoiding mercury is to avoid your intake of older fish and larger fish (particularly the kind of fish that feast on smaller fish). That includes shark, swordfish, king mackerel, tilefish, orange roughy and others.

The FDA classifies fish as “best choice,” “good choice” and “choices to avoid” according to their mercury levels. You can see their recommendations here.

Zumpano suggests that if you do choose fish that are higher in mercury, you can lower your risk of exposure to toxins by removing the skin and surface fat before cooking.

Mercury while pregnant or breastfeeding pregnancy

People who are pregnant or nursing should avoid eating fish high in mercury. That’s because exposure to mercury can cause brain damage or developmental delays in a growing fetus.

The FDA recommends people who are pregnant or breastfeeding should aim for two or three servings of “best choice” fish per week, or one serving of fish from the “good choice” list.

Kids should stick to only eating fish from the “best choices” list.

Chart: Best fish for omega-3

Zumpano says the best fish for your diet are the ones that are high in omega-3 and low in mercury.

The following chart shows some of the fish highest in omega-3, as well as advice from the FDA regarding their mercury levels. Omega-3 values are based on a 3-ounce serving size, per the U.S. Department of Agriculture. Note that omega-3 content can vary based on whether they’re eaten raw or how they’re cooked.

*Note: Canned white tuna is typically albacore tuna. Canned tuna known as “chunk light” is usually skipjack tuna. Canned chunk light tuna has a lower level of omega-3 (0.23 grams per 3 ounces). Canned skipjack tuna is listed as a “best choice” for mercury content by the FDA.

Other sources of omega-3

Not everyone enjoys fish. And some people can’t eat it because they follow a vegetarian or vegan diet or have an allergy.

You’re in luck, though. There are a variety of plant-based foods that also contain omega-3 fatty acids (the ALA kind), according to the National Institutes of Health. They aren’t as rich a source of omega-3 as sources that come from fish, but they can still be beneficial. And they don’t run the risk of mercury contamination.

In order for your body to use the nutrients from ALA, it needs to convert it first to EPA and then DHA. It’s not a terribly efficient system. That’s why getting EPA and DHA directly from fish sources is preferred when possible.

What about fish oil supplements?

Fish oil supplements are essentially a pill form of omega-3.

Except the research on the benefits of fish oil supplements has been … fishy. Some studies have shown benefits, but those results have come into question recently. A 2021 study even found that high doses of fish oil have no effect on reducing major cardiac events in people who are at high risk for them. Many cardiologists aren’t prescribing fish oil supplements these days, and the over-the-counter versions haven’t been proven to offer much benefit (if any).

Zumpano says the controversy about fish oil supplements underscores the need for getting omega-3 in your diet through whole foods, like fish. “Getting nutrients from food sources is always going to be a better route than relying on supplements.”