Which fish is the healthiest in the world? A dietitian's guide

October 30, 2025 •

2 min read

According to health guidelines, eating fish at least twice a week is beneficial for heart health. Finding which fish is the healthiest in the world involves balancing high omega-3s, low mercury, and other essential nutrients for optimal wellness.

Quick Summary

This guide examines various fish species, comparing key nutritional content and mercury levels to identify the most beneficial choices for a balanced diet.

Key Points

Sardines and mackerel lead in omega-3s: These small, oily fish are exceptionally rich in heart-healthy fats and low in mercury.
Choose small fish for low mercury: The smaller size and shorter lifespan of fish like sardines and herring result in less accumulated mercury.
Canned is a nutritious option: Canned sardines and salmon are convenient, affordable, and, with edible bones, offer high calcium.
Prioritize wild salmon: Wild-caught salmon is leaner, cleaner, and higher in essential minerals compared to some farmed varieties.
Limit large predatory fish: Species like swordfish, king mackerel, and bigeye tuna should be consumed sparingly due to higher mercury levels.
Variety is key: Rotating between different low-mercury, high-omega-3 fish ensures a wide range of vitamins and minerals.

The Nutritional Power of Fish

Fish and seafood are nutritional powerhouses, offering lean protein, essential vitamins, and minerals. Omega-3 fatty acids, particularly EPA and DHA found in oily fish, are key for heart and brain function, reducing inflammation, and potentially lowering chronic disease risk. Fish also provides vitamin D, vitamin B12, selenium, and iron, crucial for immune function, bone health, and energy.

Key Factors for Choosing Healthy Fish

Selecting healthy fish involves considering several factors:

Omega-3 Content: Oily fish like salmon, mackerel, and sardines are rich in omega-3s.
Mercury Levels: Smaller fish lower on the food chain, such as sardines, have lower mercury compared to large predators like king mackerel and swordfish.
Sustainability: Look for certifications like MSC for responsibly sourced fish.
Contaminants (Wild vs. Farmed): Wild fish can be leaner and have more minerals, while farmed fish quality varies depending on practices.

The Contenders for Healthiest Fish

There isn't one single "healthiest fish," but these are top choices:

Sardines

High in omega-3s, calcium, and vitamin D, sardines have very low mercury levels. Available fresh or canned, they're a convenient and affordable superfood.

Salmon

Wild-caught Alaskan salmon is an excellent source of omega-3s, vitamin D, and B12 with low mercury. Farmed salmon is also nutritious; choose responsibly-farmed options.

Mackerel

Atlantic mackerel is a sustainable, nutrient-dense fish packed with omega-3s, protein, selenium, and vitamin B12, crucial for immune function and energy. It has low mercury, unlike king mackerel.

Herring and Trout

Herring offers high omega-3s and vitamin D. U.S.-farmed rainbow trout is sustainable, rich in omega-3s, vitamin B12, and vitamin D.

Comparing the Healthiest Options


Feature	Sardines	Atlantic Mackerel	Wild Salmon	Rainbow Trout
Omega-3s (per 3.5oz/100g)	~1,463-1,600mg	~2,298mg	~2,150mg	~733mg
Mercury Level	Low	Low (avoid King)	Low	Low
Key Nutrients	Calcium, Vitamin D, B12, Iron	B12, Selenium, Protein	Vitamin D, B12, Selenium, Protein	Vitamin D, B12, Selenium
Typical Cost	Low (canned)	Moderate	High (seasonal)	Moderate
Sustainability	Excellent	Good	Excellent (Alaskan)	Good (farmed)

Canned Fish: A Smart, Convenient Choice

Canned fish is an affordable and convenient option. Canned sardines and salmon are high in omega-3s, and the bones provide calcium. Choose canned "light" or skipjack tuna for lower mercury than albacore. Check sodium levels.

Fish to Limit or Avoid

Limit or avoid high-mercury fish, especially for pregnant women and children. High-mercury species include large predators like:

Shark
Swordfish
King Mackerel
Marlin
Bigeye Tuna

Conclusion: Making the Best Choice for Your Health

Prioritizing fish with high omega-3s and low mercury, such as sardines, wild salmon, Atlantic mackerel, and rainbow trout, is key for health. A varied diet including these fish, along with convenient canned options, helps meet nutrient needs. For more information, consult resources like the Scripps Health guide on choosing healthy fish.

Frequently Asked Questions

Sardines and Atlantic mackerel are often cited for their combination of high omega-3 fatty acid content and very low mercury levels, making them top contenders.

Wild-caught salmon is often leaner and generally has lower contaminant levels than farmed salmon. However, farmed salmon can still be a very healthy source of omega-3s, and responsible farming practices are improving.

Canned sardines and salmon are considered the healthiest canned options. They are high in omega-3s and, with the bones, are an excellent source of calcium.

Yes, but they should choose fish with low mercury levels, like salmon, sardines, and trout. The FDA advises limiting or avoiding high-mercury species to protect fetal and neurological development.

Most health organizations, like the American Heart Association, recommend eating two servings of non-fried fish per week, particularly oily fish.

White fish like cod are excellent sources of lean protein, but they contain significantly less omega-3 fatty acids than oily fish such as salmon or mackerel. They are still a nutritious part of a balanced diet.

Tuna is a great source of protein, but varieties like albacore and bigeye contain higher mercury levels. Opt for canned 'light' (skipjack) tuna more frequently, and limit higher-mercury types to once per week or less.