Six opened tins arranged in a grid on a white surface, sardines, anchovies, mackerel, tuna, mussels and smoked trout, each with a small card, beside a lemon and a slice of dark bread

Is Tinned Fish Healthy? Mercury, Omega-3, Salt and Calcium, Species by Species

The question arrives in two forms. One is from a person who has heard that tinned fish is a superfood and wants to know whether the hype is true; the other is from a person who has heard that fish contains mercury and wants to know whether the tin is safe. The answer to both is yes, with a table. Small, short-lived, oily fish, which is what most of a conserva shelf is, are among the best sources of omega-3 fats in any diet and sit at the very bottom of the mercury scale; large predatory tuna sits higher. Bones in the tin mean calcium. Oil-packing means more fat and better absorption of some nutrients. Salt varies fivefold between tins and is the thing to read the label for. Here are the numbers by species, the official guidance, and what it means for how often to eat them. Our label guide explains the rest of the tin; this page is the nutrition.

The table

Per 100 grams (about 3.5 ounces, a typical tin drained), from USDA and FDA data. Omega-3 is EPA plus DHA combined. Mercury tiers follow the FDA and EPA advice for people who are pregnant or breastfeeding and for children, which is the strictest standard and therefore the useful one.

Fish Omega-3 (EPA+DHA), grams Mercury tier (FDA/EPA) Sodium range, mg Calcium, mg (with bones) Protein, g
Sardines, in oil, with bones About 1.0 to 1.5 Best choice 300 to 500 About 380 About 25
Anchovies, in oil, fillets About 1.5 to 2.0 Best choice 3,000 to 4,000 (cured in salt) About 230 About 29
Mackerel, Atlantic, in oil About 1.5 to 2.5 Best choice (Atlantic and Pacific chub); avoid king mackerel 300 to 500 About 240 with bones About 23
Tuna, light (skipjack), in oil About 0.2 to 0.3 Best choice 300 to 400 Low About 29
Tuna, albacore (white), in oil About 0.7 to 1.0 Good choice (one serving a week) 300 to 400 Low About 26
Mussels, in escabeche or oil About 0.5 to 0.8 Best choice 300 to 600 Low About 20
Smoked trout, in oil About 0.6 to 1.0 Best choice (freshwater, farmed) 500 to 900 (smoked) Low About 22

Two things stand out. Sardines, anchovies and mackerel deliver five to ten times the omega-3 of light tuna at the same mercury tier, which is why the conserva shelf is a better health proposition than the tuna aisle. And anchovies carry ten times the sodium of everything else, because they are salt-cured rather than cooked; they are a seasoning to be eaten by the fillet, not a fish to be eaten by the tin, and the salt is the reason.

Omega-3: why the small fish win

The long-chain omega-3 fats EPA and DHA are made by algae and concentrate up the marine food chain in the fat of fish. Oily fish store them in their flesh; lean fish store them in their livers, which is why cod fillet has little and cod liver oil has a lot. Sardines, anchovies, mackerel and herring are oily and small, so their flesh is rich in omega-3 and, because they are low on the food chain and short-lived, poor in the contaminants that accumulate in older, larger fish. The American Heart Association recommends two servings of fish a week, preferably oily, and a single tin of sardines meets a day's worth of the intake most guidelines suggest. Canning does not destroy omega-3; the tin is heated once, and the fats are stable in the sealed, oxygen-free environment, which is part of why a sardine ages well in the tin, as our shelf-life piece notes.

Mercury: the food chain, not the tin

Methylmercury enters the ocean from natural and industrial sources and builds up in fish that eat other fish over long lives: swordfish, king mackerel, bigeye tuna, shark. A sardine lives a few years and eats plankton; it has almost none. The FDA and EPA sort commercial fish into three tiers for the most sensitive groups, and nearly everything on a conserva shelf is in the best tier, which they suggest at two to three servings a week even in pregnancy. Albacore tuna, a larger fish, is in the middle tier at one serving a week. Skipjack, the "light" tuna in most tins and in the Spanish and Portuguese premium tins, is in the best tier. Ventresca, the belly cut, comes from the same fish as the loin and carries the same tier. The practical rule: small fish, no limit that most people would reach; albacore, once a week; and the big predators are not sold in tins here anyway.

Salt: the number to read

Sodium is where tins differ most, and it is on the label. A plain sardine in olive oil runs 300 to 500 milligrams per tin, a modest share of the 2,300 the Dietary Guidelines set as a daily ceiling. Smoked fish runs higher. Fish in sauces, escabeche, tomato, piri-piri, vary with the sauce. And salt-cured anchovies run to several grams per 100, which is why a tin of them is a month of seasoning, not a lunch. For anyone watching sodium, the rules are: plain oil-packed over sauced, drained and rinsed if it matters, and anchovies by the fillet. Our anchovy guide explains why the salt is the point of the fish.

Calcium and the bones

A tin of whole sardines, bones in, carries about as much calcium as a glass of milk, because the canning process softens the bones until they are edible and unnoticeable. Boneless, skinless fillets have lost that. If calcium matters, buy the whole fish, which is also the traditional and better tin, as the cannery piece explains.

The oil

Olive oil-packed fish carries more calories and more fat than water-packed, and most of that fat is the monounsaturated fat of the oil plus the fish's own omega-3, which the oil helps preserve and which the body absorbs better with fat present. Draining the oil removes some of the fish's fats that have leached into it; eating the oil, on the toast, keeps them. Water-packed tuna is the lean choice; olive-oil-packed sardines are the choice for the fats that were the reason to eat fish. A tin in "vegetable oil" or "soybean oil" is neither and is the sign of a lesser tin.

BPA and the can

The lining of food cans has historically used bisphenol A, and concern about it led most premium European canneries and many American ones to move to BPA-free linings over the past decade; many now say so on the tin. The FDA's position is that BPA is safe at the levels found in food, while some other regulators have tightened limits. If it concerns you, look for the BPA-free statement; the producers on our shelf are asked, and the ones who have made the change tend to print it.

Who should be careful

People who are pregnant or breastfeeding, and young children: follow the FDA tiers above, which put nearly all conservas in the best category and albacore at once a week. People on a sodium-restricted diet: plain oil-packed, drained, and anchovies sparingly. People with a shellfish allergy: mussels, cockles and clams are shellfish. People taking blood thinners: the omega-3 in a normal serving of fish is not a concern, but concentrated fish oil supplements are a question for a doctor. Everyone else: a tin of small oily fish a day is within every guideline and better than most lunches. None of this is medical advice; the sources below are the primary ones, and a doctor or dietitian knows your particulars.

The verdict, by species

Sardines: the best all-round tin for health, especially with bones. Mackerel: the richest in omega-3; choose Atlantic or chub, not king. Anchovies: superb fats, a seasoning's worth of salt. Skipjack tuna: lean protein, low mercury, low omega-3. Albacore and ventresca: more fat and flavor, once a week for the sensitive groups. Mussels and cockles: good protein, iron and B12, modest omega-3. Smoked trout: good fats, watch the salt. The tins are at 263 Josephine Street in Cherry Creek, Denver, and ship nationwide from theambrosianpantry.com, and the complete guide is where to start choosing.

Sources & Further Reading

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