Tuna and mercury: how much is in it and how dangerous is that?

Many are aware that tuna contains mercury. It is less well known how high the mercury content of tuna products actually is and what danger it represents for us. More on this here.

You can buy tuna in different variations in the can or fresh. The fish is used in different ways as a pizza tab, salattopping, ingredient for pasta sauces or as a tuna steak with side dishes.

Due to its high protein content and the omega-3 fatty acids it contains, tuna is popular. Possible pollutants that the fish absorbs in its lifetime makes it less healthy, especially for certain groups of people.

Another problem: According to the WWF, around 60 percent of all tuna stocks are considered overfished. This means that tuna consumption is problematic not least from an ecological point of view. You can find out more about this here: sustainable tuna – is that possible?

Mercury emissions decreases, but not the salary in tuna

Although the mercury emissions in Europe, North America and former Soviet countries have decreased significantly since the 1970s, the mercury concentration in tuna has remained largely constant. This is because large quantities of mercury are deposited in the ocean in depths of over 50 meters and continuously get into the food chain, as a study in 2024 found.

The researchers around Anaïs Médieu from the Université de Bretagne Occidentale require increased measures to reduce the global mercury emissions. The international Minamata Convention, which has been ratified by 137 countries, has actually existed since 2017.

Where does mercury come from and how dangerous is it?

According to the AOK, the fact that mercury gets into tuna at all is particularly due to the industrial burning of coal and garbage. This creates vapors that contain the pollutant and drop into the sea. There, mercury in plankton enriches. The plankton is in turn eaten by certain fish species. Finally, larger predatory fish like the tuna eat the small plankton -eating fish and can accumulate a relatively high mercury content in the body in the course of their life – mainly in the form of highly toxic methyl mercury.

According to the Federal Environment Agency (UBA), mercury damages the animal’s nervous system and can cause certain changes in behavior. In addition, animals with a high mercury content may be less reproductive.

Mercury can also have fatal consequences for people, according to the UBA. Because even in the human body, the pollutant gets into the central nervous system and can do great damage there. Pregnant women in particular should avoid mercury, because the fabric can damage the brain development of the unborn child.

Studies confirm that damage to the nervous system by mercury, for example in tiredness, behavioral changes, headaches, cognitive restrictions, hearing loss and hallucinations. Mercury can also limit the function of the cardiovascular system.

Tuna and mercury: How risky is the fish?

In the EU, a regulation regulates the approved maximum value of mercury in food. For predatory fish, the limit is a milligram per kilogram according to the AOK.

The latest examination of tuna for mercury contained in Germany the Stiftung Warentest in 2016. Scientists took a close look at 20 tuna cannons and tuna steaks. In every sample, mercury could be detected, but in none of the products examined, however, the results were above the limit value of the EU. On the contrary: everyone was far below.

The German Society for Nutrition also classifies tuna as healthy food. With one to two portions a week, consumers should not worry about the mercury content inside. Only pregnant women and breastfeeding should restrict or avoid tuna consumption.

But the 2024 study gives reason to concern: On average, the mercury concentration was around a microgram (millionth gram) per gram of fish-which corresponds exactly to the limit of the EU.

By the way: Real organic tuna (i.e. with EU organic seal) has not yet existed often, since it almost always comes from wild catches that this seal does not cover. Other seals such as the natural land seal for sustainable fishing guarantee less animal suffering and more environmental awareness, but not necessarily lower mercury values. And finally there is also mercury in tuna from aquacultures. Because even in this form of husbandry, the predatory fish are fed with fish flour and fish oil that come from the sea from prisoners.

Conclusion: How much tuna should it be?

According to the DGE, more than one or two portions of tuna a week shouldn’t be anyway. The latest findings indicate that tuna perhaps even more damage to eating our health could even harm more than use.

From an ecological and social point of view, it also makes sense to do without fish. The reasons for this range from overfishing, cruel fishing methods and a killed bye to illegal fishing, which is based on criminal practices and massive violations of human rights.

If you should come on the table once, we recommend preferring organic fish. Seals such as Naturland stipulate stricter guidelines than, for example, the MSC or the ASC seal. You can find out more here: