Back in the 1950s, canned tuna was basically the Wonder Bread of protein — cheap, everywhere, and nobody asked questions about it. You grabbed a few cans off the shelf, mixed them with mayo, and that was lunch. Simple. But our understanding of what’s actually swimming around inside those little metal cans has changed a lot since then. Today, the labels on canned tuna tell a story most shoppers walk right past. And frankly, the difference between reading those labels and ignoring them could be the difference between a perfectly fine meal and a dose of something you really don’t want building up in your body.
Light vs. white
Here’s where things get a little absurd. Walk down the canned fish aisle and you’ll see dozens of nearly identical-looking cans. The branding is cheerful. There’s usually a fish on the label, sometimes a wave. Everything screams “healthy!” and “convenient!” But the single most important distinction — the one that actually affects your health — comes down to one word: “light” or “white.” That’s it. And most people treat it like a flavor preference rather than what it really is, which is a mercury indicator.
Chunk white tuna is almost always albacore. Albacore is a bigger, longer-lived fish, and the longer a tuna lives, the more mercury it accumulates. According to FDA data, mercury levels in chunk white tuna can be up to three times higher than those found in light canned tuna products. Three times. For two cans that cost roughly the same and sit next to each other on the same shelf.
Light canned tuna, on the other hand, is typically made from skipjack — a smaller species that reaches maturity faster and doesn’t live long enough to stockpile heavy metals. The mean mercury concentration for light canned tuna is about 0.126 parts per million, compared to 0.35 PPM or higher for albacore. So when someone says “always check the label,” they’re not being dramatic. They’re telling you to look for one word that could genuinely matter to your health over time.
Why mercury builds up
Mercury contamination in fish isn’t some rare fluke. Pretty much all fish carry at least trace amounts of the stuff because the water they live in is contaminated with heavy metals — a gift from decades of industrial pollution. But tuna are predators. They eat smaller fish. And those smaller fish have already absorbed mercury from their own food and environment. So the mercury concentrates upward through the food chain. Bigger tuna eat more, live longer, and accumulate more. It’s basically compound interest, but terrible.
The FDA lists fresh or frozen bigeye tuna at a startling 0.689 PPM — the worst of all tuna species. Yellowfin comes in at 0.354 PPM. Even fresh albacore clocks 0.358 PPM. Compare that to skipjack’s 0.144 PPM, and you start to see the picture. Size matters. Lifespan matters. And what ends up in your can depends entirely on which species the company decided to put in there.
That brings up another thing people rarely consider: the label doesn’t always tell you the species name in plain language. “White” tuna means albacore. “Light” tuna usually means skipjack. But not always. Some brands blend species, and the labeling laws around seafood aren’t exactly designed with total transparency in mind. If the can doesn’t specify the species at all? That’s probably not a great sign. Reputable companies tend to be upfront about what’s inside.
Brand-to-brand surprises
You’d think mercury levels would be roughly consistent across brands selling the same type of tuna. Nope. A Consumer Reports study found that Chicken of the Sea’s albacore canned tuna had ten times more mercury than its own light tuna. Ten times! Meanwhile, Wild Planet’s albacore and skipjack varieties actually had similar mercury levels. So the brand you choose and the way they source their fish can make a measurable difference.
Even more unsettling: that same study found that about one in five individual cans had significantly higher mercury content than the brand’s average. One in five. There’s no way to tell from the outside which can might be the outlier. It’s a bit like a lottery nobody signed up for.
For most healthy adults, the FDA says two to three servings of tuna a week is safe. But Consumer Reports was more cautious, recommending that adults eat no more than five ounces of albacore per week. And for pregnant people? Their recommendation was to skip canned tuna entirely. That’s a much harder line than the FDA takes, which tells you something about how uncertain the science still is around safe exposure levels. The takeaway: if you eat tuna regularly, paying attention to which brand and species you buy is one of the few things you can actually control.
Oil, water, and packaging
Speaking of label details people skip over — the packing medium matters too, though for totally different reasons than mercury. Tuna packed in water is lower in calories and fat. Sounds like a win, right? Except that water-packed tuna also loses some of its omega-3 fatty acids into the water, which most people drain off and throw away. It also dilutes the natural flavor of the fish, which is why water-packed tuna can taste a bit flat and generic.
Oil-packed tuna, usually in vegetable or soy oil, seals in more of those nutrients and delivers a richer taste. The trade-off is extra calories and fat. Neither option is objectively better — it depends on what you’re using it for. Making a tuna melt where flavor counts? Oil-packed. Watching calories? Water-packed. But it’s a choice you should be making deliberately, not accidentally because you grabbed whatever was closest.
Along the same lines, there’s the can-versus-pouch debate. Tuna pouches are lighter and don’t need a can opener, which is nice for packed lunches or hiking. But they cost more per ounce and don’t protect the fish as well — the tuna can turn to mush in a backpack. Cans are cheaper, sturdier, and have a shelf life of around four years. One real thing to watch for: BPA. The cheapest canned varieties sometimes use linings that contain BPA, a chemical you probably don’t want leaching into your tuna. Look for cans labeled BPA-free. Some brands even have pop-top lids now, so the can opener excuse doesn’t hold up much anymore.
How the fish got caught
If you care at all about the environmental side of this (and even if you only care a little), the fishing method printed on the label is worth a glance. Some industrial tuna operations use enormous nets or long-line setups that catch everything in their path — dolphins, sea turtles, sharks, you name it. That’s called bycatch, and it’s one of the biggest problems in commercial fishing. It quietly devastates populations of species that have nothing to do with tuna.
The better options? Look for labels that say “pole-caught,” “pole and line,” or “trawl.” These methods are more selective and do less collateral damage. You might also see phrases like “school-caught” or “free school,” which indicate the company took measures to reduce bycatch. And here’s a useful rule of thumb: companies that use responsible fishing practices almost always brag about it on the can. If you don’t see any mention of fishing methods at all, that silence probably means something.
Skipjack tuna, already the winner in the mercury category, also tends to be the more sustainable choice. They reproduce quickly and reach maturity faster than albacore or yellowfin, which means their populations bounce back more easily. Some fishing companies have shifted toward targeting skipjack specifically to give other species room to recover. So choosing light tuna isn’t just better for your body — it’s less destructive to the ocean, too. That’s a rare twofer.
Or just eat sardines
Sometimes the best solution to a problem is sidestepping it altogether. If mercury in tuna stresses you out — or if you’re pregnant, nursing, or feeding young kids — there are canned fish alternatives with dramatically lower mercury levels. Sardines top the list at just 0.013 PPM. That’s roughly ten times less mercury than light tuna. Anchovies come in at 0.016 PPM. Canned salmon sits at a comfortable 0.014 PPM, though honestly, canned salmon is kind of an acquired taste that many people never actually acquire.
Sardines in particular have had a real moment lately — they’re packed with omega-3s, calcium, and protein, and they’re cheap. You can get a good can for under two bucks. The flavor is stronger than tuna, sure, but toss them on some crackers with hot sauce or mash them into pasta and you might be surprised. They’re the smarter canned fish choice if mercury is your main concern.
But let’s be real — most people aren’t giving up their tuna salad for sardines anytime soon. And they don’t need to. The point isn’t to avoid canned tuna. It’s to buy it with your eyes open. Read the label. Choose light over white. Check for the fishing method and BPA-free packaging. Maybe don’t eat it every single day. That’s about ten seconds of effort at the grocery store, and it’s the difference between being a smart shopper and just being a shopper.
