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If you have been following a gut- and brain-healthy diet, such as the traditional Mediterranean diet or a Pescatarian diet, you already know that seafood and plant-based foods should be your main sources of meat, replacing red meat. Seafood and poultry should make up about 25% of your total dietary intake. Importantly, you should enjoy the fish without being obsessed with fears of consuming toxins with your meal.

“Fish are a lean, healthy source of protein and some of them deliver those heart- and brain-healthy omega-3 (also called n-3) fatty acids that [are good for your brain].”

Fish are a lean, healthy source of protein–and the oily kinds, such as salmon, tuna, and the family of small fish such as sardine, mackerel, and anchovies–deliver those heart- and brain-healthy omega-3 (also called n-3) fatty acids that you should be getting in your diet. Studies have shown that while consuming a higher ratio of n-6 to n-3 fatty acids tends to promote inflammation, consuming a more balanced ratio can reduce inflammation. In addition, omega-3 fatty acids have been shown to promote neurogenesis (the development of new nerve cells) in a particular region of the hippocampus, the dentate gyrus and there is a strong correlation between omega-3 intake and hippocampal-dependent memory tasks. In the traditional Western diet, polyunsaturated fatty acids (PUFAs) are currently consumed at a ratio of approximately 1:16, whereas it has been estimated that our ancestors consumed a diet with a ratio closer to 1:1. Smaller, fatty fish, like sardines have the highest concentration of omega-3 fatty acids as a consequence of their consumption of omega-3 rich algae. By feeding on the small fish, larger fish like salmon enrich their meet with omega-3 fatty acids. So the decision to select fish with high omega-3 concentration is an easy one. However, there are two additional considerations that you should consider before making your choice. The fish should have low levels of contaminants in particular mercury and PCBs, and it should come from a sustainable fishery, and should not use fishing methods damaging other ocean species.

“Fortunately, there are trustworthy sources of information which can help you chose the right fish…”

Fortunately, there are trustworthy sources of information which can help you to navigate this dilemma, such as The Blue Ocean Institute and Seafood Watch, the program run by the Monterey Bay Aquarium. These programs have combined data from leading health organizations and environmental groups such as the Environmental Defense Fund (EDF) to come up with a list of seafood that’s good for you and good for the environment.

The following is adapted from an excellent blog by Brierley Wright, published by One Medical, a national, modern primary care practice pairing 24/7 virtual care services with inviting and convenient in-person care at over 100 locations across the U.S.

According to Seafood Watch, there are six fish/shellfish that are healthy for you and the planet.

1. Farmed Oysters
A 3-ounce serving contains over 300 mg of omega-3s and about a third of the recommended daily values of iron). Oysters are not only good for you, but for the environment. Oysters feed off the natural nutrients and algae in the water (which provides them with large amounts of omega-3), and which improves water quality.

2. Wild caught Pacific Sardines
The tiny, inexpensive canned sardine which has been popular in Europe for a long time, contains more omega-3s (1,950 mg!) per 3-ounce serving than salmon, tuna, or just about any other food; it’s also one of the few foods that’s naturally high in vitamin D. Many fish in the herring family are commonly called sardines. Sardines are a highly sustainable food source as they have a fast reproduction rate. Pacific sardines have rebounded from both overfishing and a natural collapse in the 1940s.

3. Wild caught Alaska Salmon
The numbers of wild salmon returning to spawn in Alaska’s rivers is being closely monitored, and if the numbers begin to dwindle, the fishery is closed before it reaches its limits. This close monitoring, along with strict quotas and careful management of water quality, means Alaska’s wild-caught salmon are both healthier (they pack 1,210 mg of omega-3s per 3-ounce serving and carry few contaminants) and more sustainable than just about any other salmon fishery.

4. Farmed Freshwater Coho Salmon
Freshwater coho salmon is the first–and only–farmed salmon to get a Super Green rating. All other farmed salmon still falls on Monterey Bay Aquarium’s Seafood Watch “Avoid” list for a few reasons. Many farms use crowded pens where salmon are easily infected with parasites, may be treated with antibiotics, and can spread disease to wild fish (one reason Alaska has banned salmon farms). Also, it can take as much as three pounds of wild fish to raise one pound of salmon. Coho, however, are raised in closed freshwater pens and require less feed, so the environmental impacts are reduced. They’re also a healthy source of omega-3s–one 3-ounce serving delivers 1,025 mg.

5. Farmed Rainbow Trout
Nearly all the trout you will find in the market is farmed rainbow trout. In the US, rainbow trout are farmed primarily in freshwater ponds and “raceways” where they are more protected from contaminants and fed a fish meal diet that has been fine-tuned to conserve resources.

6. Troll- or pole-caught Albacore Tuna from the US or British Columbia
Many tuna are high in mercury but albacore tuna–the kind of white tuna that’s commonly canned–gets a Super Green rating as long as it is “troll- or pole-caught” in the US or British Columbia. The reason: Smaller (usually less than 20 pounds), younger fish are typically caught this way (as opposed to the larger fish caught on longlines). These fish have much lower mercury and contaminant ratings and those caught in colder northern waters often have higher omega-3 counts. The challenge: You need to do your homework to know how your fish was caught or look for the Marine Stewardship Council (MSC) blue eco label.

Fish to Avoid

A number of environmental organizations have advocated taking many fish off the menu. The large fish listed below are just six examples of popular fish that are both depleted or threatened by extinction and, in many cases, carry higher levels of mercury and PCBs. Unfortunately, many restaurants continue to serve these fish on their menus and customers pay high prizes for what they think is a special treat.

1. Bluefin Tuna
In December 2009, the World Wildlife Fund put the bluefin tuna on its “10 for 2010” list of threatened species, alongside the giant panda, tigers, and leatherback turtles. Though environmental groups are advocating for protected status, the bluefin continues to command as much as $177,000 a fish. Bluefin have high levels of mercury and their PCBs are so high that EDF recommends not eating this fish at all.

2. Chilean Sea Bass or Patagonian Toothfish)
Slow-growing and prized for its buttery meat, Chilean sea bass has been fished to near depletion in its native cold Antarctic waters. The methods used to catch them–trawlers and longlines–have also damaged the ocean floor and hooked albatross and other seabirds. The EDF has issued a consumption advisory for Chilean sea bass due to high mercury levels.

3. Grouper
High mercury levels in these giant fish have caused EDF to issue a consumption advisory. Groupers can live to be 40 but only reproduce over a short amount of time, making them vulnerable to overfishing.

4. Monkfish
This strange fish resembles a catfish in that it has whiskers and is a bottom-dweller, but its light, fresh taste made it a staple for gourmets. The fish is recovering some after being depleted, but the trawlers that drag for it also threaten the habitat where it lives.

5. Orange Roughy
Like grouper, this fish lives a long life but is slow to reproduce, making it vulnerable to overfishing. As Seafood Watch puts it: “Orange roughy lives 100 years or more–so the fillet in your freezer might be from a fish older than your grandmother!” This also means it has high levels of mercury, causing EDF to issue a health advisory.

6. Salmon (farmed)
Most farmed salmon (and all salmon labeled “Atlantic salmon” is farmed) are raised in tightly packed, open-net pens often rife with parasites and diseases that threaten the wild salmon trying to swim by to their ancestral spawning waters. Farmed salmon are fed fish meal, given antibiotics to combat diseases and have levels of PCBs high enough to rate a health advisory from EDF. Recently, however, freshwater-farmed coho salmon have earned a Best Choice status from Seafood Watch. Consumer pressure may encourage more farms to adopt better practices.

7. US freshwater fish – Hot off the press
According to a research study just published in the journal Environmental Research, eating just one serving of freshwater fish, caught in lakes and streams each year could have the same effect as drinking water heavily polluted with “forever chemicals” for an entire month, a new study finds. According to the study, the equivalent monthlong amount of water would be contaminated at levels 2,400 times greater than what’s recommended by the Environmental Protection Agency’s (EPA) drinking water health advisories. The research added that locally caught freshwater fish are far more polluted than commercial catches with per- and polyfluorinated substances (PFAS) — so-called forever chemicals that are notorious for their persistence in the body and the environment.

“Three criteria make it relatively easy for an informed consumer to decide which fish to buy”

In summary, using the 3 criteria of health benefit, low contamination and sustainability makes it relatively easy for an informed consumer to decide which fish to buy. While many popular fish types are on the Avoid List, the top three choices for you and the planet are small fatty fish, oysters and wild caught Alaskan salmon.

By Emeran Mayer, MD and E. Dylan Mayer