Most people assume all canned tuna is basically the same. You grab a can, toss it in the cart, maybe compare prices for a second, and move on. But the difference between a can labeled “chunk light” and one labeled “chunk white” is a lot bigger than you’d think — and it has nothing to do with taste. One carries significantly more mercury than the other, and the label tells you everything you need to know if you bother to read it.
Not all tuna is the same fish
Here’s something that catches a lot of people off guard: there are over two dozen species of fish that fall under the “tuna” umbrella. That’s a huge range. When you pick up a can at the grocery store, you might be getting skipjack, albacore, yellowfin, or something else entirely, and the label doesn’t always make it obvious. Companies tend to use terms like “light” and “white” instead of the actual species name, which means you have to know the code.
“Chunk white” almost always means albacore. That’s one of the bigger tuna species. “Chunk light” usually means skipjack, which is much smaller and reaches maturity faster. This distinction matters more than most shoppers realize, because the size and lifespan of a fish directly affects how much mercury it stores in its body. Bigger fish that live longer accumulate more. It’s that simple.
The mercury numbers are kind of wild
So let’s talk actual data. According to the FDA, light canned tuna has a mean mercury concentration of about 0.126 parts per million. That’s pretty low. Fresh or frozen skipjack comes in slightly higher at 0.144 PPM — still reasonable. But when you jump to albacore? You’re looking at 0.35 to 0.358 PPM. Yellowfin is similar, sitting around 0.354 PPM. And bigeye tuna, which you’ll mostly find fresh rather than canned, clocks in at a startling 0.689 PPM.
That means albacore tuna — the “white” stuff — can contain roughly three times the mercury of the light variety. Three times. And that gap gets even more dramatic when you look at individual brands. One consumer study found that Chicken of the Sea’s albacore had ten times more mercury than its light tuna. Wild Planet, on the other hand, had fairly similar levels across its products. Brand consistency varies wildly, which honestly makes the whole thing feel a little like a lottery.
Why mercury in fish is such a big deal
Mercury isn’t one of those things your body just flushes out easily. It builds up. For healthy adults eating high-mercury fish even once a week, fatigue can become a constant companion. Longer-term exposure has been linked to problems with blood pressure regulation, fertility issues, and even memory loss. These aren’t fringe concerns — they’re documented effects from regular overconsumption.
For kids and pregnant women, the stakes are higher. Mercury exposure in young children can cause developmental delays and learning disabilities. The FDA says two to three servings of low-mercury fish per week is generally safe for most people, including children and pregnant women. But a separate study from Consumer Reports took a harder line on albacore specifically, recommending adults cap their intake at five ounces per week. They went so far as to suggest pregnant people skip canned tuna altogether. That’s a pretty significant difference in guidance depending on who you ask.
And that’s not even the only label issue
Mercury gets all the attention, but there’s another thing on the label worth your time: how the tuna was caught. Some companies use massive industrial nets that scoop up everything in their path — not just tuna, but dolphins, sea turtles, sharks, and other marine life that wasn’t supposed to be part of the deal. This is called bycatch, and it’s a genuine environmental problem that’s been quietly reshaping ocean ecosystems for decades.
Look for cans that say the fish were caught via “pole,” “pole and line,” or “trawl” — these are considered better methods when it comes to reducing harm. Terms like “school-caught” or “free school” are also good signs. One thing I’ve noticed? Companies that do things the right way tend to slap it right on the front of the can. If you’re flipping a can around and can’t find any mention of how the fish was caught, that silence probably isn’t accidental.
Oil-packed or water-packed — it actually matters
This one surprises people. Most folks just grab whatever they’ve always grabbed — oil or water — without thinking much about it. Water-packed tuna has fewer calories and less fat, which sounds like a win. But here’s the tradeoff: the water dilutes the fish’s natural juices and flavors, and you lose some omega-3 fatty acids in the process. If you’re draining the can and mixing it with mayo anyway, you might not notice. But it’s real.
Oil-packed tuna, usually packed in vegetable or soy oil, does a better job of sealing in nutrients and flavor. The taste tends to be richer. The downside is the calorie count goes up. Neither option is objectively wrong — it depends on what you’re optimizing for. If flavor matters most to you, go with oil. If you’re counting calories, water is fine. Just know you’re making a tradeoff either way.
Those tuna pouches at the store
You’ve probably seen the plastic tuna pouches hanging on the shelf near the cans. They’re lightweight, easy to open without a can opener, and honestly pretty convenient for packing a lunch. But there’s a catch. They cost more per ounce, and the flexible packaging doesn’t protect the fish inside the way a rigid can does. Take one on a hike and you might open it to find tuna mush instead of clean chunks.
Cans, on the other hand, maintain the texture and shape of the fish better and tend to have a longer shelf life — about four years on average. That said, not all cans are created equal either. Some cheaper brands use materials that might contain BPA, a chemical you don’t want leaching into your food. Look for cans that say “BPA-free” on the label. A few brands now offer pop-top lids too, so the whole “I don’t have a can opener” excuse doesn’t hold up as well as it used to.
When the label is trying to trick you
Here’s the thing that gets under my skin. Seafood labeling laws in the U.S. don’t always prioritize the consumer. Some companies lean into vague or misleading language on purpose. They know most people don’t have time to research what “premium tuna” or “select catch” actually means (spoiler: usually nothing specific). The less information they give you, the more suspicious you should be.
A good rule of thumb: reputable companies are generally happy to answer questions about where their fish comes from and how it was caught. They’ll have that information on their website, if not on the can itself. Companies that dodge these questions or make it hard to find answers? Red flag. If you’re buying a brand you’ve never tried, spend two minutes looking it up on your phone. It takes less time than debating which cereal to buy, and the stakes are higher.
Maybe just eat sardines instead?
If all of this mercury talk has you second-guessing tuna entirely, there are alternatives that sit much lower on the mercury scale. Sardines come in at just 0.013 PPM — practically nothing. Anchovies are close behind at 0.016 PPM. Canned salmon lands around 0.014 PPM too, though I’ll be honest, canned salmon has a taste and texture that not everyone loves. It’s polarizing.
None of this means you need to stop eating tuna. Light canned tuna is still considered a low-mercury option by the FDA, and it’s packed with protein, vitamins, and those omega-3 fatty acids that keep showing up in every health article ever written. Eating it a couple times a week is fine for most people. Just don’t make it your daily lunch and you’re probably in good shape. Variety in your fish intake helps spread out any risk.
So what should you actually do at the store
You don’t need to memorize all of this. Seriously. The next time you’re standing in the canned fish aisle, just look for these words: “light” or “skipjack” for lower mercury, “pole and line” or “free school” for responsible fishing, and “BPA-free” for safer packaging. That covers the big stuff. If the can is weirdly cheap and vague about everything, leave it on the shelf.
The simplest takeaway: flip the can over, spend ten seconds reading the label, and pick light tuna caught with responsible methods — your future self will thank you for it.
