Can you eat too much tinned tuna?

Tinned tuna is a popular and nutritious lunch option, affordable and convenient for busy individuals. However, concerns about excessive consumption often arise, mainly due to mercury content. Mercury is a naturally occurring element in the environment that enters waterways through natural and human activities, eventually becoming methylmercury, which fish absorb.

Larger predatory fish tend to accumulate higher mercury levels due to longer lifespans. While larger fish like shark, swordfish, and marlin can contain more mercury, most tinned tuna in Australia comes from smaller species like skipjack and yellowfin, with much lower mercury levels. Health authorities set a weekly mercury intake limit (provisional tolerable weekly intake), which pregnant women should adhere to more strictly.

Research on mercury concentrations in canned tuna sold in Australia is limited, but international studies suggest that a 95g can of tuna contains about 13mg of mercury. For a four-year-old weighing 20kg, one can of tuna may use up about 20% of their weekly mercury allowance, indicating that two to three cans a week, commonly used for sandwiches, is unlikely to pose a risk.

Mercury poisoning symptoms arise from prolonged exposure to high levels, including numbness, muscle weakness, coordination issues, vision and hearing problems, and memory difficulties. These symptoms are unlikely to occur from typical tinned tuna consumption in Australia. While some Australian fish contain higher mercury levels, they should be limited to one serving per week.

Eating a variety of protein sources, including tinned tuna, ensures a balanced diet and provides essential nutrients.