Fish and seafood are commonly regarded among the healthiest foods on the planet. They are central components of some of the healthiest eating patterns, such as the Nordic, Mediterranean, and Japanese diets. But the reality is not all fish are created equal, and there are tremendous differences within this broad category of species. In fact, some fish can be downright dangerous to your health. In this article, we’ll reveal the best and worst fish to eat, and the criteria that sets them apart from one another. Enjoy!

In this worst fish to eat article, we will cover:

1. Why You Need to Be Eating Fish
2. The Top Vitamins in Seafood
3. The Health Benefits of Eating Seafood
4. Best & Worst Fish to Eat (Our Grading System)
5. Omega-3 Content
6. Mercury Levels
7. Sustainability
8. Seafood Mislabeling
9. Best Fish to Eat
10. Worst Fish to Eat
11. Summary

Why You Need to Be Eating Fish

Before I let the cat out of the bag about the worst fish to eat, let’s talk about why you should be eating seafood on the regular in the first place. After all, there’s good reason health organizations like the American Heart Association urge folks to eat seafood at least 2 – 3 times a week. ^{1, 2}

For starters, the best seafood choices, which I’ll reveal shortly (patience, my friend), are packed with two super-duper-awesome nutrients:

• Protein
• Omega-3 Fatty Acids

Chances are you’re pretty familiar with these two nutrition all-stars, but if you’d like for me to bore you with details, you can find out more about the benefits of higher-protein diets and omega-3 fatty acids.

In short, higher-protein diets seem to be a linchpin for overall health, appetite management, body composition, recovery from exercise, building/maintaining muscle, healthy aging, and glycemic balance to name a handful of benefits.

Meanwhile, omega-3s are essential fatty acids (meaning you need to get them through food and/or supplemental sources) that are mission-critical for cellular health, healthy levels of inflammation, and for supporting the health of your heart, brain, mood, metabolism, eyes, skin, and immune system.

The Top Vitamins in Seafood

Beyond this dynamic duo, the best sources of seafood have some additional nutrition ammo up their sleeves…or fins…or scales…or shells…including:

• Vitamin B12. Among its many functions, B12 energizes the brain and nervous system and protects it from the buildup of potentially toxic compounds.
• Vitamin D. Suffice it to say, there are very, very few food sources of naturally-occurring vitamin D (aka, the “sunshine vitamin”). The role and benefits of vitamin D, which is much more like a hormone than a vitamin, far surpass healthy bones, and research has linked vitamin D deficiency to obesity, diabetes, cardiovascular disease, fatigue, and more.
• Choline. Often overlooked, choline is an essential nutrient often grouped with B vitamins, and it is a building block for the neurotransmitter (a scientific name for a chemical that helps the nervous system communicate effectively and efficiently) acetylcholine, which is important for memory, mood, muscle control, and more. It is a neuronutrient that works hand-in-hand with B12 to recycle potentially neurotoxic compounds. And not surprisingly, higher choline intake has been associated with better cognitive performance. ³
• Selenium. Another overlooked (and under-consumed) nutrient, selenium is a trace mineral that also serves as an antioxidant. Low selenium has been linked to declining brain health and cognitive function. It can also help boost testosterone levels. It’s also important for converting thyroid hormone to its active form, and research has shown people who don’t consume enough selenium have lower levels of metabolically active thyroid hormone.
• Iodine. Speaking of thyroid, seafood is also a good source of iodine, which is necessary for the production of thyroid hormone. Having said that, too much iodine can actually be problematic for thyroid function, but only when it’s combined with inadequate levels of selenium. In other words, you need balance between iodine and selenium, and guess what? Seafood contains both! Winner, winner, chicken (of the sea) dinner!

The Health Benefits of Eating Seafood

Considering that seafood can be so nutrient-dense, the following list of 7 benefits of regular fish and seafood consumption may not come as too much of a surprise (although it’s darn impressive nonetheless):

1. Reduced Risk of All-Cause Mortality. In a robust review study (a meta-analysis of 12 studies involving 672,389 participants) published in the European Journal of Clinical Nutrition, researchers from China found that fish consumption significantly lowered the risk of all-cause mortality, which is science speak for death from all causes. In fact, they found that consuming 60 grams (about 2 ounces) of fish per day was associated with a 12% reduction in all-cause mortality. ⁴

2. Reduced Risk of Cardiovascular Mortality. In yet another large review study (a meta-analysis of 14 studies involving 911,348 participants) published in the journal Public Health Nutrition, researchers found that fish consumption was significantly and inversely associated (i.e., lowered) with the risk of death from cardiovascular disease (CVD). For instance, every 20-gram per day (about ¾ of an ounce) increment in fish consumption lowered the risk of CVD mortality by 4%. ⁵

3. Reduced Risk of Cardiovascular Disease. Among their many potential benefits, the omega-3 fatty acids EPA and DHA have been shown to have anti-inflammatory, antithrombotic (i.e., blood thinning), and antiarrhymic (i.e., support normal heart rhythms) properties, improve blood lipids (e.g., triglycerides), and aid in circulation (e.g., vascular relaxation). Along these lines, the AHA recommends consuming seafood twice a week to help reduce the risk of congestive heart failure, coronary heart disease, and sudden cardiac death. In addition to these cardioprotective effects, research has also shown that fish consumption is beneficial for the prevention of acute coronary syndrome, such as heart attack. ⁶

4. Reduced Risk of Stroke. Considering the above, it makes sense that researchers from the University of North Carolina found that fish consumption is also protective against the risk of stroke, particularly ischemic stroke (which is the most common type of stroke usually caused by a blood clot that blocks or plugs a blood vessel in the brain). ⁷ In yet another large review study (a meta-analysis of 16 studies involving 402,127 participants) published in the European Journal of Clinical Nutrition, the researchers found consuming fish as little as once a week lowered the risk of stroke by 14%.

5. Better Cognitive Function. Thanks to their density of neuronutrients (e.g., DHA, B12, choline), the right types of seafood are some of the most powerful brain-boosting foods. While seafood may not be a quick-fix smart drug that leaves you feeling limitless within minutes of consumption, multiple studies have shown that higher fish intake is associated with better cognitive function later in life. ^{8, 9} In other words, eating more seafood is saving for retirement—except you’re socking away for a healthy mental retirement. This point can’t be overstated. Cognitive decline doesn’t happen overnight; it’s degenerative over time, and you can stave off the chronic decay by making better choices (e.g., exercising, eating more seafood) now.

6. Reduced Risk of Depression. In an extensive review study (including a meta-analysis of 26 studies involving 150,278 participants) published in the Journal of Epidemiology and Community Health, Chinese researchers found that fish consumption was inversely associated with depression. They found men and women who consumed more fish had up to a 17% lower risk of depression. ¹⁰

7. Beneficial Effects on Metabolic Syndrome. Several studies have shown that fish consumption can lower the risk of type 2 diabetes although there are some inconsistencies in the research. ¹¹ However, a recent study published in the journal Nutrients found that consuming fish at least once a week was associated with a significant decrease in triglycerides, waist circumference, and blood pressure along with an increase in HDL cholesterol—four factors that constitute Metabolic Syndrome, which is a constellation of metabolic abnormalities that increase the risk for cardiovascular disease and type 2 diabetes. ¹²

What Makes a Good Fish to Eat?

While these findings are promising and lend considerable credence to the long-standing guidance to eat more fish, it’s critical to point out that it’s not all sunshine and rainbows when it comes to fish consumption. Believe it or not, other studies have shown no such benefits with increasing fish consumption. Even more surprising, you won’t have any trouble digging up studies showing that fish consumption is associated with negative outcomes.

In other words, although there’s a substantial amount of supportive data on fish consumption, the data is not definitive. When you think about it, this inconsistency makes a great deal of sense. “Fish” is a very, very broad category of food, and as you’ll see, not all fish are created equal.

When drawing the line between the best and worst fish to eat, which I’ll do in just a moment, there are several factors to consider:

1. Omega-3 Content
2. Mercury Levels
3. Sustainability Concerns
4. Seafood Fraud/Mislabeling

Step 1: Omega-3 Content

While all seafood tends to be a good source of protein, the playing field is not quite as equal when it comes to omega-3 content, which is arguably the most compelling reason to eat more fish. These bad boys are so mission-critical that the American Heart Association recommends adults consume at least 500 mg of EPA and DHA (and more is often better).

The following seafood options are the richest in omega-3s (providing at least 500 mg of EPA and DHA per 3-ounce cooked portion):

• Herring
• Salmon
• Mackerel
• Sardines
• Mussels
• Rainbow Trout
• Oysters
• Anchovies
• Pollock
• Herring
• Albacore
• Sablefish
• Striped Bass
• Halibut

Step 2: Mercury Levels & Other Toxins

What’s just as important as what’s in your fish is what’s not. Unfortunately, most of the bodies of water the fish we eat inhabit are far from pristine. In fact, due to decades of industrial activity and pollution, there are a few potential toxicants found in seafood we need to keep a very close eye out for. And public enemy number one is mercury, which poses serious health risks.

Fish contain a specific form of mercury called methylmercury, which is a neurotoxin that causes brain and nervous system damage. Methylmercury is also toxic to the kidneys, liver, and heart. Here you are trying to eat “healthy” by fitting more fish into your diet, yet you may literally be poisoning yourself!

While pregnant and nursing mothers are most likely to be warned of the potential dangers of mercury in seafood, methylmercury affects people of ALL ages. And it can attack your brain, nervous system, and kidneys the same way it does a child’s. The most common signs of methylmercury poisoning include:

• Loss of peripheral vision or blurred vision
• Loss of hearing
• Numbness, burning, and tingling (“pins and needles”) feelings in the hands, feet, and around the mouth
• Lack of coordination of movements
• Impaired speech, hearing, and walking
• Muscle weakness
• Fatigue

All that said, all fish contain some level of mercury. There’s no such thing as a mercury-free fish. However, some fish contain substantially more (i.e., dangerously high levels of) mercury than others. For instance, long-lived predators—like swordfish, shark, orange roughy, and tuna—tend to have the highest levels of mercury making them the worst fish to eat. On the other hand, there are low-mercury fish.

Low Mercury (Eat Up to 3 Servings/Week):

• Salmon
• Sardines
• Anchovies
• Rainbow Trout
• Atlantic Mackerel
• Pacific Mackerel
• Shrimp
• Tilapia
• Catfish
• Scallops
• Clams
• Mussels
• Oysters

Moderate Mercury (Eat Up to 3 Servings/Week):

• Mahi Mahi
• Halibut
• Canned Tuna
• Lobster
• Snapper
• Perch
• Cod

High Mercury (Eat no more than 1 serving/week):

• Yellowfin Tuna
• Striped Seabass
• Trout
• Bluefish
• Chilean Seabass
• Grouper
• Albacore Tuna
• Walleye

Highest Mercury (Avoid):

• Orange Roughy
• Shark
• Swordfish
• King Mackerel
• Marlin
• Bluefin Tuna
• Big Eye Tuna

In addition to mercury, there are other potential toxicants, such as industrial chemicals (PCBs and dioxins) and pesticides (DDT), that can be found in fish. Like mercury, large predatory, long-living fish tend to end up with the greatest concentration of these toxins as well.

There’s also one unsuspecting “healthy” fish you need to be wary of: farmed salmon, which are often raised in conditions riddled with pesticides, feces, bacteria, and parasites. And while they may be low in mercury, farmed salmon have been shown to contain high concentrations of other potentially health-derailing contaminants, like PCBs, dioxins, and chlorinated pesticides. ^{13, 14}

Step 3: Sustainability

When it comes to seafood, another critical variable is sustainability. Monterey Bay Aquarium’s Seafood Watch® program defines sustainable seafood as seafood from sources, whether fished or farmed, that can maintain or increase production without jeopardizing the structure and function of affected ecosystems.

In other words, sustainable seafood is seafood either caught or farmed in ways that take into consideration the long-term vitality of the species, the wellbeing of the body of water, and the livelihoods of the fisheries-dependent communities.

Along those lines, it’s very important to consider the impact your dietary choices have on the ocean and freshwater ecosystems. Not only do you want to choose fish high in omega-3s and low in mercury, you should also make ocean-friendly choices.

The Seafood Watch program, which launched in 1999, provides science-based, peer-reviewed sustainability ratings for commercial fish species. That’s my kinda resource!

Step 4: Seafood Mislabeling

So, you’re starting to put the pieces together. We want to eat seafood that’s high in omega-3s, low in mercury, and sustainably caught. Sounds like a plan, right? Not so fast. There’s one more very important concern we have to discuss: Seafood mislabeling, which, when done intentionally, is also known as seafood fraud.

Seafood fraud is the all-too-common, misleading practice of purposefully mislabeling seafood to increase profits. Talk about fishy business! This is a global problem that has been studied and exposed all over the world.

For instance, in a recent study published in the journal Food Research International, researchers examined 203 seafood samples from 12 key species collected from various importers, processing plants, and retailers in Ontario, Canada. Their findings revealed that 32% of the samples overall were mislabeled, and mislabeling occurred at the import stage, processing plants, and at retailers (where the highest rates of mislabeling were reported). ¹⁵

That’s just the start of it. When it comes to seafood fraud, the number one watchdog is Oceana, the largest international advocacy organization focused solely on ocean conservation. Oceana recently conducted one of the largest seafood fraud investigations in the world to date, collecting more than 1,200 samples from 674 retail outlets in 21 states to determine if they were honestly labeled. They found one in three seafood samples were mislabeled.

Here are some key findings from the Oceana study:

• Mislabeling was found in 27 of the 46 fish types tested (59%)
• Snapper (87%) and tuna (59%) were the most commonly mislabeled fish
• Only 7 of the 120 red snapper samples were honestly labeled
• 84% of the white tuna samples were actually escolar, a type of fish that can cause serious digestive issues for some folks who eat more than a few ounces
• 44% of all grocery stores, restaurants, and sushi venues sold mislabeled seafood
• In Seattle, every snapper sample was mislabeled
• In Austin, Chicago, Washington, DC, and New York, every sushi venue sold mislabeled fish
• Southern California had the highest mislabeling rate nationwide
• Tilefish, a fish on the FDA’s DO NOT EAT list, was sold in place of halibut and red snapper
• King mackerel, another fish on the DO NOT EAT list, was sold in place of grouper

Pretty scary stuff, isn’t it? Pisses you off more than a little bit, doesn’t it? Me too. Not only is seafood fraud dishonest, the guilty parties are stealing your hard-earned money, and they’re putting you in harm’s way.

So, What are the Best Fish to Eat?

Tying all the pieces together, when it comes to choosing between the best and worst fish to eat, you want to choose seafood that’s:

• High in omega-3 fatty acids
• Low in mercury and other contaminants
• Sustainably sourced

Of course, even after we’ve identified the best seafood choices, we have to be very cautious about seafood fraud. With all that in mind, here are is the best fish to eat:

• Wild Salmon
• Pacific Sardines
• Mussels
• Rainbow Trout
• Atlantic Mackerel

Other “Good Choices” (which are high in omega-3s and low/moderate in mercury but not as sustainably sourced) include:

• Oysters
• Anchovies
• Pollock
• Herring
• Albacore Tuna (troll- or pole-caught)
• Sablefish

The Worst Fish to Eat

While there are many seafood options that would be best to limit or avoid (see the charts above), the following are drop-dead, no-thank-you, avoid-at-all-costs worst fish to eat:

• King Mackerel
• Marlin
• Orange Roughy
• Shark
• Swordfish
• Tilefish
• Big Eye Tuna
• Bluefin Tuna

To the list of worst fish to eat, we also need to talk about fried fish, which is usually cod, perch, walleye, and catfish. But the fact of the matter is that the type of fish doesn’t really matter. They’re usually deep-fried in poor-quality “RBD” (i.e., refined, bleached, deodorized) oils, which tend to be highly inflammatory. They also contain artificial trans fatty acids, which are not healthy in ANY amount due to their definitive health-derailing properties.

In addition, there are a few more that deserve “honorable mention.” I wouldn’t necessarily call them the worst fish to eat, but I’d limit their consumption:

1. Tilapia. Even though it’s low in mercury and sustainably sourced, tilapia contains a negligible amount of omega-3 fatty acids. Even more, tilapia (particularly farm-raised) is relatively high in omega-6 fatty acids, which can be pro-inflammatory when consumed in excess.

Researchers from Wake Forest have gone so far as to say, “For individuals who are eating fish as a method to control inflammation, it is clear from these numbers that tilapia is not a good choice. All other nutritional content aside, the inflammatory potential of hamburger and pork bacon is lower than the average serving of farmed tilapia.” ¹⁶

Honestly, I think the rub on tilapia is a bit of a stretch. While there’s no question that most people overconsume omega-6 fats (particularly in relationship to omega-3s), this omega imbalance has nothing to do with eating too much tilapia (which only contains about a ½ gram per serving) and everything to do with the ubiquity of highly refined vegetable and seed oils high in omega-6s (e.g., soybean, corn, safflower, sunflower, cottonseed, peanut, and canola).

2. Farmed Salmon. We already talked about a major strike against farmed salmon, which is often littered with potential toxicants in the form of PCBs, dioxins, and chlorinated pesticides.

What’s more, unlike wild salmon, which thrive on a natural diet rich in omega-3 fatty acids, farmed salmon typically feed on pellets made from corn and soy. As mentioned above, these heavily-subsidized commodities have a relatively high concentration of omega-6 fatty acids. And because you are what you eat, so do farmed salmon. In fact, farmed salmon contain a ratio of omega-6 to omega-3 fats that’s nearly 3 times higher than wild salmon—this is the same omega imbalance we’re trying to drive down by eating fish. ¹⁴

3. Grouper. Poor Mr. Grouper, it doesn’t have too much going for it. If you take a look back, we’ve put together a heck of a checklist you can use to make great seafood choices, and grouper comes out on the wrong side in all categories. It’s low in omega-3s. It’s high in mercury. It’s not sustainably sourced. It’s a prime suspect in seafood fraud. And if that weren’t enough, grouper is not exactly the most attractive-looking fish. Poor guy.

Worst Fish to Eat: A Recap

You are now armed with all the knowledge of both the best and worst fish to eat. You know it’s a great idea to eat healthy, nutritious, and delicious seafood at least twice a week, and you know the best choices are high in omega-3 fats, which are anti-inflammatory, help boost immunity, and have far-reaching benefits on virtually every aspect of health. The best choices are also sustainably caught and low in mercury, a toxin that can attack your brain, nervous, system, kidneys, liver, and heart.

Please refer to the charts I’ve shared above so you can consistently make the best seafood choices. And take time to ask questions at your local markets and restaurants. Make sure you’re getting what you’re paying for.

If you’d like more information, I encourage you to check out the resources made available by the following incredible organizations: Environmental Working Group, Monterrey Bay Aquarium’s Seafood Watch program, Ocean, and the Environmental Defense Fund. We all want to help you be a highly educated consumer!