Do we need to be concerned about mercury levels in tuna?

Written by Eliza Freney (The Rugby Dietitian)

I talk about the nutritional benefits of tuna a lot. This means I also get asked about the mercury content a lot. Mercury has a bit of a reputation for needing to be avoided but what most people don’t realise is there is quite a safe way to consume tuna without needing to be concerned about the mercury content. So let's do what we are taught to do as health care professionals: look at what the evidence says, and put it in perspective.

The short version? For most healthy adults — and certainly for the athletes I work with — tuna is nothing to be nervous about.

Why mercury is in fish at all

Mercury occurs naturally in the ocean, and it also gets there through human activity. Once it's in the water, small fish take up tiny amounts, bigger fish eat those small fish, and bigger fish again eat those. At each step up the food chain the mercury concentrates. So the fish carrying the most tend to be the big, long-lived predators sitting near the top: swordfish, marlin, broadbill, shark/ flake, and southern bluefin tuna.

Where does the tuna we commonly eat fall?

Here it helps to be specific, because "tuna" isn't one fish.

Most tinned tuna in Australia comes from skipjack and yellowfin — smaller, faster-growing species usually caught young. Less time in the ocean means less time to accumulate mercury, which is why these sit at the low end of the scale, and why food-safety advice treats a tin of tuna quite differently from a fresh swordfish steak.

Albacore, the premium white tuna, sits a step higher. Albacore carries roughly two to three times the mercury of skipjack, because it grows larger and lives a little longer. That sounds dramatic until you see it in context. Regulators still class albacore as a "good choice" — safe for the general population to eat regularly, just not in unlimited quantities.

Putting the numbers in perspective

Food Standards Australia New Zealand (FSANZ) says it's safe for everyone — including children and pregnant women — to eat two to three serves of most fish every week, where a serve is 150g. Tuna comfortably makes that list.

There's also a safety threshold called the provisional tolerable weekly intake. For a 70kg adult that works out to around 231 micrograms of mercury a week — and you'd have to work fairly hard through the tins to get near it. For most Australians, tuna a few times a week sits well within safe territory.

The fish FSANZ actually asks the general population to limit are the top-of-the-chain ones — shark/flake, swordfish, broadbill and marlin — to one serve a week, with nothing else from that list in the same week. Tuna isn't on that restricted list.

The bit people miss: size and source

Two tins labelled the same can carry quite different amounts of mercury, and it mostly comes down to the size and age of the fish that went into them. Younger, smaller fish — often the surface-caught ones — carry less. It's one of the reasons I think knowing where your fish comes from is worth more than most people give it credit for. Traceable, Australian-caught product isn't just a nice-to-have; it tells you something deeper about what you're eating.

Don't forget the other side of the ledger

Mercury gets all the airtime, but it's only half the equation. Tuna is one of the most convenient whole-food sources of high-quality protein going around, and it brings omega-3 (EPA and DHA), selenium and iodine along with it. For athletes especially, that combination — protein for repair, omega-3 for recovery — is a valuable nutrition source.

Who does need to be a bit more careful

If you're pregnant, planning a pregnancy, breastfeeding, or feeding young children, mercury deserves a little more respect — a developing brain is more vulnerable to it. The message isn't "avoid tuna," it's "be a bit more deliberate": lean on the lighter species like skipjack, and keep albacore more occasional (some guidelines suggest around one serve a week for these groups). Fish is genuinely good for a developing baby, so the goal is to keep eating it — just how much and how often.

So — should you be concerned?

Concerned, no. Aware, yes. For the vast majority of people, tuna is a safe, brilliant, affordable food that earns a place in your diet. Choose the smaller species most of the time, know where your fish is coming from, save the big predators for the occasional treat, and take a little more care if you're pregnant or feeding little ones.

Sources

Guidance current as at August 2026.

Food Standards Australia New Zealand (FSANZ) — Mercury in fish and Advice on Fish Consumption (serve sizes, provisional tolerable weekly intake, and species-specific limits). Background statement (PDF)
Better Health Channel, Victorian Government — Mercury in fish (2020 update reflecting JECFA advice; consumption guidance for the general population, pregnant women and children). betterhealth.vic.gov.au
SafeFish / Fisheries Research and Development Corporation (FRDC) — Mercury and Omega-3 Oils in Australian Seafood (Australian Total Diet Study data; low mercury in canned tuna; benefit–risk balance). frdc.com.au
US Food and Drug Administration & Environmental Protection Agency — Advice about Eating Fish (Best Choices / Good Choices classification; light/skipjack vs albacore mercury levels). epa.gov
The Conversation — Can you eat too much tinned tuna? (2026; PTWI worked example and species context). theconversation.com