A Nutritional Guide to What is the Healthiest Sea Fish to Eat?

November 6, 2025 •

4 min read

Studies have shown that people who eat seafood regularly have healthier overall diets and a lower risk of heart problems. This makes choosing the right options a key part of a healthy lifestyle, so knowing what is the healthiest sea fish to eat is an important consideration for your nutritional journey.

Quick Summary

A comprehensive guide analyzing various sea fish options based on their nutritional benefits, omega-3 fatty acid content, potential mercury levels, and sustainable sourcing. This resource helps in making informed choices for a balanced and healthy diet.

Key Points

Omega-3 Richness: Small, oily fish like sardines, mackerel, and herring are among the healthiest choices due to their high concentration of omega-3 fatty acids.
Low Mercury Content: Smaller fish, like sardines and Atlantic mackerel, have lower mercury levels compared to larger predators such as shark and swordfish, making them safer for regular consumption.
Lean Protein Benefits: White fish like cod and haddock offer high-quality, lean protein, are low in fat, and are good sources of B vitamins and selenium.
Sourcing is Key: For fish like salmon and halibut, choosing wild-caught or sustainably farmed and certified options (e.g., MSC/ASC) is vital for both health and environmental protection.
Bone Health: Eating canned sardines or salmon with the edible bones is a fantastic source of dietary calcium and vitamin D.
Moderation is Prudent: Even with healthy fish, a varied diet is best. For canned tuna, for instance, limiting intake to a few times a week mitigates mercury concerns, especially for pregnant women.

The Nutritional Power of Seafood

Seafood is a dietary powerhouse, packed with high-quality protein and essential nutrients that are vital for human health. The most celebrated component is the omega-3 fatty acid, specifically EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Our bodies cannot produce these essential fats, so we must obtain them through food. These fats are crucial for heart and brain health, helping to lower blood pressure and reduce the risk of heart attacks and strokes. Beyond omega-3s, fish provides a bounty of vitamins and minerals. Key nutrients include protein for muscle repair, vitamin B12 for nerve and blood cell health, and selenium, which supports a healthy immune system and thyroid function.

Factors for Choosing the Healthiest Fish

When selecting the healthiest fish, it's not just about nutrient content; two other critical factors come into play: mercury levels and sustainability.

Understanding Mercury Levels

Larger, longer-lived predator fish higher up the food chain tend to accumulate higher levels of methylmercury, a neurotoxin. While most fish have some mercury, the levels in small, shorter-lived species are much lower and generally not a concern for most people. For vulnerable populations, like pregnant women, breastfeeding mothers, and young children, limiting high-mercury fish is especially important.

Prioritizing Sustainability

Overfishing and certain farming practices can have negative environmental impacts. Choosing sustainably sourced seafood helps protect marine ecosystems and fish populations for future generations. Look for certifications from reputable organizations like the Marine Stewardship Council (MSC) and the Aquaculture Stewardship Council (ASC), which indicate the fish has been responsibly harvested or farmed.

Top Contenders for Healthiest Sea Fish

Oily Fish Champions: The Omega-3 Powerhouses

Salmon: A versatile and popular choice, salmon is an excellent source of omega-3s, protein, and vitamin D. Wild-caught salmon is often praised for its higher omega-3 content, but farmed salmon is also a nutritious and widely available option. Canned salmon offers a cost-effective and convenient way to include this fatty fish in your diet.
Sardines: These small, inexpensive fish are incredibly nutrient-dense. Gram for gram, canned sardines offer more omega-3s than salmon and are one of the best dietary sources of calcium and vitamin D, thanks to their edible bones. They are also low in mercury due to their position at the bottom of the food chain.
Mackerel: Rich in healthy fats, protein, and selenium, mackerel is another top pick for an oily fish. Atlantic mackerel, in particular, is noted for its low mercury content and sustainable sourcing. It's widely available fresh, canned, or smoked.
Herring: A staple in Nordic diets, herring contains a very high concentration of omega-3s, vitamin D, and selenium. Like sardines, it's a small fish and therefore low in mercury. It can be enjoyed fresh, canned, cured, or smoked.

Lean Protein Favorites

Cod: A classic white fish that is high in protein and low in fat, making it an excellent option for weight management and heart health. It provides a good source of vitamin B12, crucial for energy production. When choosing cod, prioritize sustainable options like those from Iceland or the Arctic.
Haddock: Similar to cod, haddock is another popular white fish known for its mild flavor and lean, flaky texture. It is high in protein and rich in minerals like selenium, magnesium, and potassium. Look for haddock caught in the North Sea and Iceland for the best sustainable choice.
Halibut: This fish is prized for its firm texture and mild, slightly sweet flavor. Halibut is a great source of high-quality protein, selenium, and niacin. While Atlantic halibut is a concern for overfishing, Pacific halibut from well-managed fisheries is a better alternative.

A Comparison of Healthiest Sea Fish


Feature	Salmon	Sardines	Mackerel	Cod	Halibut
Omega-3s	High	High (Higher than Salmon per gram)	High	Low	Medium
Mercury	Low (Wild) to Very Low (Farmed)	Low	Low (Atlantic & Pacific)	Low	Medium-High (Avoid Atlantic)
Protein	Excellent	Excellent	Excellent	Excellent	Excellent
Vitamin D	Excellent	Excellent (with bones)	Excellent	Low	Low
Calcium	Good (Canned)	Excellent (with bones)	Good	Good	Good

How Often to Eat Fish

The American Heart Association recommends eating two servings of fish per week, with one being an oily fish, to reap heart-healthy benefits. A serving is typically 4 ounces (113 grams). For pregnant or breastfeeding women, specific guidelines from health organizations like the FDA and EPA should be followed, limiting overall intake and avoiding high-mercury species. Eating a variety of both oily and lean, low-mercury fish helps balance nutrients and minimize potential contaminant exposure over time.

Conclusion

While many sea fish offer fantastic health benefits, a few stand out as the absolute healthiest options. Oily fish like sardines, mackerel, and salmon are the undisputed champions for omega-3 fatty acids, which are crucial for heart and brain health. For a lean protein alternative, cod and haddock are excellent, low-mercury choices. The key to a healthy diet is variety, so incorporating different types of fish throughout the week is recommended. Always consider sustainability by choosing certified seafood and being mindful of mercury levels, especially for certain populations. By making informed choices, you can enjoy the many nutritional rewards that seafood provides.

Learn more about sustainable choices from the Marine Stewardship Council.

Frequently Asked Questions

Yes, canned tuna is a good source of protein and omega-3s. However, stick to chunk light or skipjack varieties, which are smaller and lower in mercury than albacore tuna. Moderation is key, especially for pregnant women who should limit intake to 4 cans or 2 steaks per week.

Wild-caught fish generally have a leaner profile and may have slightly higher levels of omega-3s, but farmed fish can also be nutritious with consistent omega-3 levels. Sustainability practices can vary, so look for certifications like MSC (wild) and ASC (farmed).

Larger, predatory fish with long lifespans tend to have higher mercury levels. It is advisable to limit or avoid species like shark, swordfish, king mackerel, marlin, and tilefish.

Health organizations like the American Heart Association recommend eating at least two servings of fish per week, with one being an oily fish, to gain heart and brain health benefits from omega-3 fatty acids.

While salmon is an excellent choice, sardines offer more omega-3 fatty acids per gram and are a better source of calcium and vitamin D if eaten with their soft bones. Both are healthy options, but sardines provide a more concentrated nutrient profile.

If you are not a fan of oily fish, you can still get some omega-3s from lean fish like cod and halibut, though in smaller amounts. Other non-fish sources include walnuts, flaxseed, and canola oil.

Both fresh and canned fish can be highly nutritious. Canned varieties, such as sardines and salmon, often have longer shelf lives and can offer higher levels of calcium (from edible bones). Choose options packed in water to manage sodium intake.