The healthiest fish to eat are small, oily, cold-water species that pack high levels of omega-3 fatty acids and low levels of mercury. Salmon, mackerel, sardines, anchovies, and herring top the list. Eating fish two to four times per week is associated with a 23% lower risk of dying from heart disease compared to rarely eating fish, and bumping that to five or more times per week pushes the reduction to 38%.
The SMASH Fish: Five Top Choices
A useful acronym for remembering the best options is SMASH: Salmon, Mackerel, Anchovies, Sardines, and Herring. These five cold-water species share a few key traits. They’re rich in omega-3s (specifically EPA and DHA, the two forms your body uses most efficiently). They’re naturally high in vitamin D, a nutrient most people don’t get enough of from food alone. And the smaller ones, like sardines and anchovies, have edible bones that provide a meaningful amount of calcium and phosphorus for bone health.
Here’s how they compare on omega-3 content per 100 grams of fish (roughly a 3.5-ounce serving), based on data from Oregon State University:
- Atlantic mackerel: 2.5 grams of combined EPA and DHA
- Atlantic farmed salmon: 1.8 grams
- Chinook (king) salmon: 1.4 grams
- Sockeye salmon: 1.2 grams
- Sardines (canned): 1.0 gram
- Rainbow trout: 0.5 grams
Lake trout deserves a mention here too. Certain varieties deliver up to 3.0 grams of combined EPA and DHA per serving, rivaling mackerel. Standard lake trout comes in around 1.6 grams, still an excellent choice.
Why Small Fish Have an Edge
Sardines, anchovies, and herring sit low on the food chain. They eat plankton, not other fish. That means they accumulate far less mercury and other environmental contaminants than large predators like swordfish, king mackerel (distinct from Atlantic mackerel), and shark. The FDA places sardines, anchovies, and herring in its “Best Choices” category, meaning their average mercury concentration falls at or below 0.15 micrograms per gram. Fish in this category are safe to eat two to three servings per week, even for pregnant women and young children.
Fish with mercury levels above 0.46 micrograms per gram land in the “Choices to Avoid” category. That includes shark, swordfish, tilefish from the Gulf of Mexico, and bigeye tuna. Between those extremes, “Good Choices” fish (0.15 to 0.46 micrograms per gram) are fine at one serving per week.
There’s also a built-in safety factor in many fish. Selenium, a mineral found naturally in seafood, appears to offer some protection against mercury’s harmful effects. Research from the U.S. Geological Survey found that the selenium-to-mercury ratio in Chinook salmon averaged 27:1, far above the 1:1 threshold considered protective. Even walleye, which had the lowest ratio studied, still came in at 3.4:1.
Wild Salmon vs. Farmed Salmon
Both are good sources of omega-3s, but the nutritional profiles differ more than most people realize. A 3-ounce fillet of wild salmon has roughly half the total fat of farmed salmon. Farmed salmon does deliver more omega-3s, but it also carries more than double the saturated fat. For people watching their saturated fat intake, wild salmon offers a leaner package.
The contaminant picture is more concerning. PCB levels in farmed salmon are about 16 times higher than in wild-caught fish, according to Cleveland Clinic’s analysis. PCBs are industrial pollutants that persist in the environment and accumulate in fat tissue. Antibiotic use in fish farming has reportedly been reduced in recent years, but the extent of ongoing use remains unclear. Wild salmon carries none of that uncertainty. If budget allows, wild-caught sockeye or pink salmon are the cleaner option. If farmed is what’s available, it’s still a better choice than skipping fish entirely.
Canned Fish Is Just as Nutritious
Fresh fish isn’t always practical or affordable. The good news is that canning doesn’t meaningfully degrade omega-3 content. Canned sardines and mackerel remain good sources of EPA and DHA, and any oily fish (canned or fresh) is a far better source of omega-3s than a lean white fish like tilapia. Tufts University notes that the differences in omega-3 content between canned and fresh fish often come down to the specific species, where it was harvested, and what it ate, not the canning process itself.
The main thing to watch with canned fish is sodium. Sardines packed in tomato sauce tend to be higher in sodium than those canned in olive oil or water. Checking the nutrition label and choosing low-sodium versions when possible helps keep your overall intake in check.
How You Cook Fish Matters
You can start with a perfectly omega-3-rich fillet and lose a significant portion of those benefits through cooking. Research published in ScienceAsia tested multiple methods and found that frying resulted in the lowest retention of EPA and DHA across every fish species studied. Grilling also led to notable losses.
Steaming and baking in foil preserved the most omega-3 content, with statistically significant advantages over frying and grilling. The difference comes down to heat type: moist-heat methods (steaming, foil-baking) protect the delicate fatty acids, while dry-heat methods (frying, open grilling) break them down. If you’re eating fish specifically for the heart-health benefits, steaming or baking in foil is the way to go. Poaching works on the same principle.
Microplastics: A Growing Concern
One newer issue worth knowing about is microplastic contamination. Research from the Black Sea found that virtually all commercial fish sampled contained microplastics, with bottom-dwelling species carrying higher concentrations than fish that live in open water. Pelagic fish (those swimming near the surface, like sardines, mackerel, and herring) tend to have lower microplastic loads than demersal species that feed along the ocean floor.
This is another point in favor of the SMASH group. Small pelagic fish not only carry less mercury, they also appear to pick up fewer microplastics than bottom-feeders. The overall health benefits of eating fish still outweigh the risks for most people, but choosing smaller, open-water species tilts the equation further in your favor.
Practical Recommendations
Aim for two to three servings of fish per week, prioritizing oily, cold-water species. A serving is about 4 ounces raw (roughly the size of a deck of cards after cooking). Here’s a simple way to think about your best options:
- Top tier (highest omega-3, lowest contaminants): sardines, anchovies, herring, Atlantic mackerel, wild salmon
- Excellent choices: farmed salmon, lake trout, rainbow trout
- Good but eat less often: albacore tuna, halibut, snapper (one serving per week due to moderate mercury)
- Avoid: shark, swordfish, king mackerel, bigeye tuna, tilefish from the Gulf of Mexico
If you dislike the taste of fish, canned sardines mashed into pasta sauce or mixed into grain bowls are an easy entry point. Canned salmon works well in patties or salads. These budget-friendly options deliver the same core benefits as a fresh fillet from the fish counter, at a fraction of the cost.