What is the healthiest fish in the world?

December 14, 2025 •

4 min read

Gram for gram, canned sardines have even more of the powerhouse omega-3 fatty acid than salmon, according to a registered dietitian. But pinpointing exactly what is the healthiest fish in the world requires weighing multiple factors like mercury content, sustainability, and specific nutrient profiles.

Quick Summary

This guide explores the most nutrient-dense fish options, examining factors like high omega-3 content, low mercury levels, and sustainability to help you make informed seafood choices for better health.

Key Points

Oily fish are key: The most nutrient-dense fish are typically fatty, cold-water species rich in omega-3s, like sardines, salmon, and mackerel.
Small fish, less mercury: Smaller fish, such as sardines and anchovies, are lower on the food chain and therefore contain less mercury than large predatory fish.
Consider canned options: Canned sardines and salmon offer a cost-effective, convenient, and highly nutritious alternative to fresh fish, and sardines contain more calcium when bones are included.
Check sustainability certifications: For ethical and environmental reasons, look for certifications like the MSC or ASC to ensure your fish is sourced responsibly.
Balance mercury risk: While avoiding high-mercury fish like swordfish and king mackerel is wise, the benefits of eating low-mercury fish generally outweigh the risks.
Eat a variety: Consuming a mix of low-mercury fish is the best strategy to maximize nutritional benefits and minimize risks from any single type of contaminant.

The Primary Health Benefits of Eating Fish

Eating fish offers a wealth of nutritional benefits for overall health. Fish is a lean source of high-quality protein, essential for muscle maintenance and overall body function. Beyond protein, fatty fish are particularly rich in marine-based omega-3 fatty acids, specifically EPA and DHA, which are linked to powerful anti-inflammatory effects and support heart and brain health. Studies have shown that consuming fish regularly can be associated with a reduced risk of heart disease, stroke, and dementia. Many fish varieties also supply crucial vitamins and minerals, including vitamin D, B12, selenium, and iron, nutrients that many people's diets lack.

The Top Contenders for 'Healthiest Fish'

While a single answer for the healthiest fish is impossible due to varying nutritional needs and concerns, a few types consistently rise to the top due to their ideal balance of nutrients, low contamination, and sustainability.

Sardines: The Omega-3 King

These small, oily fish are nutritional powerhouses. Because you consume the bones when eating canned sardines, they are an excellent source of calcium and vitamin D. They are low in mercury due to their position at the bottom of the food chain and are a very sustainable choice. Their high omega-3 content is particularly noteworthy, often surpassing that of salmon gram for gram.

Salmon: A Crowd-Pleasing Favorite

Salmon is widely recognized for its rich omega-3 fatty acid content, high-quality protein, and ample vitamin D. Both wild-caught and farmed salmon offer similar omega-3 levels, though nutritional content can vary based on feed for farmed fish. Wild-caught Alaskan salmon is often cited for its high omega-3s and lower contaminants, but farmed salmon is still a great, accessible option. For sustainability, look for certifications like the Marine Stewardship Council (MSC) or Aquaculture Stewardship Council (ASC).

Mackerel: Nutrient-Dense and Affordable

Atlantic mackerel is a small, oily fish rich in omega-3s, protein, and B vitamins, particularly B12. It is also high in selenium, an antioxidant that protects cells from damage. Like sardines, Atlantic mackerel is lower in mercury than larger mackerel species like King mackerel and is generally a sustainable choice.

Rainbow Trout: A Great Omega-3 and Vitamin D Source

Closely related to salmon, rainbow trout has a milder flavor and is an excellent source of omega-3s, lean protein, and vitamin D. When sustainably farmed in freshwater ponds, it can be a great, low-mercury option.

Anchovies: Tiny Fish, Big Nutrients

These small, oily fish are another great source of omega-3s, protein, and calcium, especially when eaten whole. Anchovies are low in mercury and a sustainable choice. While often salty when canned, they can be easily incorporated into many dishes to boost flavor and nutrition.

A Comparative Look: The Healthiest Fish Breakdown


Fish	Omega-3 Content	Mercury Risk	Other Key Nutrients
Sardines	Very High	Very Low	Calcium, Vitamin D, Iron, Selenium
Salmon	Very High	Low	Vitamin D, Vitamin B12, Selenium
Mackerel	High	Low (Atlantic)	Vitamin B12, Selenium, Protein
Rainbow Trout	High	Low	Vitamin D, Vitamin B12, Protein
Anchovies	High	Very Low	Calcium, Iron, Protein, Zinc
Cod	Low	Low	Lean Protein, B Vitamins, Selenium
Canned Light Tuna	Medium	Low	Protein, Iron, Vitamin B12

Mercury and Contamination Concerns

Mercury is a neurotoxin that can accumulate in fish, particularly larger, longer-lived predatory fish at the top of the food chain. The US Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) provide guidance to help consumers, especially pregnant or breastfeeding women and young children, limit their exposure while still getting the benefits of fish. The general recommendation is to eat a variety of fish from the "Best Choices" list (low mercury) and limit or avoid fish from the "Choices to Avoid" list (high mercury). Cooking methods do not reduce mercury levels, as the heavy metal is stored in the fish's muscle tissue. For a full list of fish choices, consult the FDA's official advice on eating fish.

Making Sustainable and Healthy Choices

Sustainability is another crucial factor when choosing seafood. Overfishing, habitat damage, and other environmental impacts can affect fish populations and marine ecosystems. By choosing sustainably sourced fish, you can support healthier oceans and ensure a future supply of seafood. Look for certifications from organizations such as the Marine Stewardship Council (MSC) or the Aquaculture Stewardship Council (ASC) when purchasing seafood. Smaller fish like sardines, mackerel, and anchovies are generally considered more sustainable as they reproduce faster and have less environmental impact.

Conclusion: Choosing Your Healthiest Fish

Ultimately, the healthiest fish is a varied diet that includes a mix of options. By prioritizing smaller, oilier fish like sardines, anchovies, and Atlantic mackerel, you can maximize your intake of omega-3s while minimizing mercury exposure. Including other great choices like salmon and trout, and being mindful of sustainability certifications, ensures a balanced and environmentally conscious approach. The key takeaway is that incorporating a variety of low-mercury, nutrient-dense seafood into your diet offers significant and wide-ranging health benefits.

A Quick Guide to the Best Choices

Sardines: A low-mercury, high-omega-3 powerhouse, especially when canned, providing excellent calcium and vitamin D.
Salmon: A widely available source of omega-3s, protein, and vitamins. Opt for wild-caught or ASC/MSC-certified farmed varieties.
Atlantic Mackerel: Another excellent source of omega-3s, protein, and B12, with a low mercury risk compared to larger species.
Rainbow Trout: A versatile fish rich in omega-3s and vitamin D. Farmed trout from inland waters is often a sustainable and low-mercury choice.
Anchovies: A tiny fish packed with omega-3s, calcium, and iron, and very low in mercury.
Cod: A great source of lean protein and B vitamins, though lower in omega-3s than oily fish.
Canned Light Tuna: A convenient, budget-friendly protein source. Choose 'light' or skipjack varieties for lower mercury levels.

Frequently Asked Questions

While it depends on specific health goals, many nutritionists point to sardines as the number one healthiest fish. They are exceptionally high in omega-3s, calcium, and vitamin D, and are very low in mercury.

Healthy white fish options include cod, haddock, and pollock. They are excellent sources of lean protein and B vitamins, though they contain fewer omega-3s than fattier fish.

Both farm-raised and wild-caught salmon are excellent sources of omega-3s and other nutrients. Wild-caught can be slightly leaner and may have lower contaminant exposure, but farmed salmon is often more affordable. Ethical farming practices are key for farmed varieties.

Fish with the highest mercury levels include shark, swordfish, king mackerel, bigeye tuna, and orange roughy. It is best to avoid or limit consumption of these, especially for pregnant women and young children.

The American Heart Association and FDA recommend eating two servings (about 3 ounces cooked each) of a variety of fish per week, especially fatty fish high in omega-3s.

The healthiest canned fish options are sardines and canned light (skipjack) tuna. Canned sardines are full of omega-3s and calcium, while canned light tuna provides lean protein with low mercury content compared to albacore.

Yes, many freshwater fish are healthy. Rainbow trout, for example, is a good source of omega-3s and vitamin D. However, it is always wise to check local fish consumption advisories for any sport-caught fish.