Tuna remains one of the most popular fish worldwide—whether it’s flaked onto a salad, tucked into a sandwich, or starring in sushi rolls. But mercury content has long made some people eye their tuna cans with suspicion, especially those who eat it often or want to serve it to children and pregnant women. Now, a team of Swedish scientists has developed an innovative technique that can reduce mercury concentrations in tuna by up to 35%—while keeping all of the fish’s prized nutrients intact. The best part? The whole process uses cysteine, a naturally occurring amino acid found in our diets.
The research behind this breakthrough comes from the Swedish University of Agricultural Sciences and Chalmers University of Technology. Their method is straightforward: immerse canned tuna in a solution containing cysteine. This is hardly outlandish—cysteine is already found in many protein-rich foods.
Przemysław Strachowski, a chemist at Chalmers University of Technology, explains: “We chose cysteine because of its strong ability to bind to mercury. This mechanism makes it possible to extract some of the mercury from the fish so it attaches to the solution and is subsequently removed.”
Laboratory tests confirmed that this approach achieves a 25% to 35% reduction in mercury concentration in tuna. The more surface area of the fish that touches the solution, the more mercury can be extracted—so if anything, this might be the best excuse ever for breaking your tuna up a little in the can!
One major reason this discovery stands out is how simple it is to apply. The researchers say the technique could be directly integrated into the canning process—with no need for new production steps or flashy equipment.
“The advantage of this type of packaging is that it remains active throughout the product’s shelf life,” says Strachowski.
This means the reduction in mercury continues gradually over time while the cans sit on the shelves, offering ever-increasing peace of mind to consumers. Tests also showed no change in the appearance or smell of the fish, and the mercury extraction process continues for up to two weeks after application, with no extra additives required.
Tuna, as every dietitian will tell you, is a nutritional powerhouse: it’s a cornerstone of the Mediterranean diet, and praised for its positive effect on health. The only fly in the ointment, so far, has been mercury—a concern especially for vulnerable populations.
“Our study shows there are alternative approaches to tackling mercury contamination in tuna, not just limiting its consumption,” says Mehdi Abdollahi, a food scientist at Chalmers University of Technology. “Our goal is to improve food safety and contribute to better human health.”
Even though these results are promising, the researchers caution that more work is needed before this can become an industry-standard solution. They’re currently focusing on how to deal with the extracted mercury and fine-tuning the process for larger-scale applications.
Looking ahead, the researchers believe this method could be refined and extended for use elsewhere in the food industry. This advance offers a significant opportunity to better utilize valuable food resources currently limited by health restrictions.
This discovery is a shining example of how science can deliver hands-on solutions to food safety challenges—allowing everyone to enjoy the nutritional rewards of tuna without having to calculate their risk with every forkful. Thanks to the magic of cysteine, the gap between healthy eating and smart risk reduction might finally be closing—one can of tuna at a time.