Fish — From Sea to Plate

by | Jul 2, 2024 | Nutrition, Real Food

Image: Shutterstock

Fish can be a nutritious and delicious part of a balanced diet, but some methods of processing and preparation have risks, and certain fish are known to accumulate higher levels of toxic mercury.

Fish can be an incredibly nutritious addition to your diet. The FDA recommends eating at least 8 ounces of fish per week on a 2000 calorie diet due to its associated health benefits. Fish is high in protein, Vitamin D, omega-3 fatty acids, iodine, and various vitamins and minerals.

But be wary, not all fish are created equal, and some methods of processing and preparation have risks. In this article, we’ll review the difference between farmed vs. wild-caught, how fish is processed and how that impacts quality, which fish are high in toxins, and which ones are especially important to incorporate into your diet (look out for the helpful trick). 

Farmed vs. Wild-Caught Fish

Farmed Fish: Fish farming, or aquaculture, involves raising fish in controlled environments. Commonly farmed species include salmon, tilapia, and catfish. Farmed fish can offer consistent supply and affordability. However, they are often criticized for potential environmental impacts and differences in nutritional quality. Farmed fish may have higher levels of omega-6 fatty acids due to their diet, which can sometimes include grains and vegetable oils. Too much omega-6  can contribute to inflammation and chronic diseases (learn more here).  

Wild-Caught Fish:
Wild fish are caught in their natural environments. These fish, such as wild-caught salmon, sardines, and mackerel,  are rich in  omega-3 fatty acids,  which have many functions in your heart, blood vessels, lungs, immune system, and endocrine system. Wild fish are also less likely to contain antibiotics and other additives compared to farmed fish. However, they can be more expensive and less sustainable, depending on fishing practices.

Processing Methods

Fish can be prepared raw, cured by marinating (like ceviche), pickled, smoked, or cooked by baking, frying, grilling, poaching, or steaming. While all can be quite delicious, it’s important to be aware of the downfalls of consuming raw, canned, and smoked fish. 

Raw: Popular in dishes like sushi and sashimi, raw fish must be fresh and handled properly to avoid foodborne illnesses. It is rich in nutrients such as omega-3 fatty acids, vitamins A and D, and essential minerals like zinc and iodine. However, certain raw fish, like tuna, can be high in mercury. Additionally, raw fish can pose a risk of parasites such as Anisakis, which can cause serious gastrointestinal issues if ingested. Freezing fish at specific temperatures for a certain period can kill these parasites and reduce the risk. 

Canned: Canning preserves fish and makes it a convenient option. Common canned fish include tuna, salmon, and sardines. Canned fish retains most of its nutrients, including protein, omega-3 fatty acids, and vitamin D. However, it can be high in sodium, and some varieties, like albacore tuna, can contain higher levels of mercury. Additionally, there are concerns about the risks of aluminum and other materials in cans leaching into the fish. Bisphenol A (BPA), used in the lining of some cans, can leach into food and has been associated with various health problems, including hormonal disruptions and increased cancer risk. 

Smoked: Smoking adds flavor and extends the shelf life of fish. Smoked salmon and mackerel are popular choices. While smoking can enhance the taste, it can also introduce harmful substances like polycyclic aromatic hydrocarbons (PAHs), which are linked to cancer. Smoked fish is also usually high in sodium. Nutritionally, smoked fish still provides a good source of protein and omega-3s but should be consumed in moderation due to potential health risks. 

The safest and healthiest methods to prepare fish include grilling, poaching, roasting, and baking. 

Toxin Concerns

Certain fish are known to accumulate higher levels of mercury, a toxic metal that can affect the nervous system. Mercury is naturally occurring, but the total concentrations of mercury have increased 450% above natural levels, due mostly to fossil fuel burning. Predatory fish at the top of the food chain, such as shark, swordfish, king mackerel, and tilefish, tend to have the highest mercury levels. Mercury exposure can lead to serious health issues, including neurological and developmental damage, particularly in fetuses, infants, and young children.  

Farmed fish tend to have higher levels of contaminants like PCBs (polychlorinated biphenyls), which are man-made chemicals that have been shown to cause adverse health effects, including cancer. 

Best Fish Choices: The SMASH Approach

For those looking to make the healthiest fish choices, the SMASH acronym can be a helpful guide: 

  • Salmon (especially wild-caught)
  • Mackerel (smaller species like Atlantic mackerel)
  • Anchovies
  • Sardines
  • Herring

These smaller cold water fatty fish are not only rich in omega-3 fatty acids but also tend to be lower in contaminants like mercury. They are often more sustainably sourced and can be found both fresh and canned. 

In conclusion, it’s best to regularly consume wild-caught SMASH fish prepared correctly to reap the health benefits while avoiding the dangers. Fish can be a nutritious and delicious part of a balanced diet, offering a range of health benefits. By understanding the differences between farmed and wild-caught fish, the impact of various processing methods, and the importance of choosing low-toxin species, consumers can make informed decisions to maximize their health benefits while minimizing potential risks.

Emily Rhodes, MPH, RD

Emily Rhodes, MPH, RD


Emily Rhodes, MPH, RD, our Food and Nutrition Writer, is a Registered Dietitian and Clinical Nutrition Manager at Keck Medicine of USC in Arcadia, CA. You can find her at the barn or in the grocery aisle reading a label.


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  2. Environmental Working Group. (n.d.). Consumer Guide to Seafood. Retrieved from
  3. National Oceanic and Atmospheric Administration (NOAA). (2021). FishWatch: U.S. Seafood Facts. Retrieved from
  4. Mayo Clinic. (2022). Mercury in fish: What’s the concern? Retrieved from
  5. U.S. Environmental Protection Agency (EPA). (n.d.). Learn about Polychlorinated Biphenyls (PCBs). Retrieved from
  6. FoodPrint. (n.d.). So Where Does All That Mercury in Fish Come From? Retrieved from

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