A study by the University of Coimbra analyzed several species of fish consumed daily in Portugal and found mercury levels above safe values in specific situations, especially when the fish is large and consumed very frequently.
The results were released by the Department of Life Sciences of the Faculty of Science and Technology, which assessed the impact of mercury present in species that are very common in Portuguese food. The objective was to understand whether habitual consumption represents a risk for groups that have fish as a weekly basis in their diet.
The heavy metal in question, mercury, especially in the form of methylmercury, accumulates in tissues over time and can affect the nervous system when ingested in excessive amounts.
Hake with higher values
Among the species analyzed, the largest hake stood out for its highest levels. According to the study, specimens over one kilogram can, when consumed cooked more than once a week, exceed references considered safe by the European Food Safety Authority (EFSA).
The horse mackerel also deserves attention. Fish measuring 35 to 40 centimeters that enter the grill five or more times a week also exceed the recommended limits.
Fish without identified risk
Despite these results, Norwegian cod, octopus and sardines presented values considered safe. Even with regular consumption, these species did not show any worrying indicators.
The researchers explain that the difference is related to the position in the food chain: the larger the fish and the more predatory it is, the greater the tendency to accumulate mercury throughout its life cycle.
How the analysis was carried out
To ensure accuracy, all sampling included fresh fish purchased in Portuguese markets, with the exception of cod, purchased already salted and dried.
The laboratory techniques replicated the usual cooking methods, boiling and grilling, and used atomic absorption spectrometry to quantify total mercury and methylmercury.
In all cases, researchers found that the cooking process increased the concentration of the metal in the food.
What it means for consumers
Experts rule out the need to remove hake or mackerel from the diet. The alert focuses mainly on the frequency and size of the fish chosen.
Consuming large hake daily or grilled large mackerel almost every week poses an increased risk, but varied choices reduce the likelihood of exceeding safety limits.
Recommendations and good practices
The team makes it clear that diversity continues to be essential in a balanced diet. Alternating species, varying cooking methods and avoiding repeated consumption of larger fish are measures that reduce exposure to mercury.
According to Elsa Teresa Rodrigues, the responsible researcher, “hake and mackerel should be consumed in moderation, while cod, octopus and sardines do not raise concerns”.
A relevant topic for Portugal
It reminds us that Portugal is among the European countries with the highest fish consumption per inhabitant, which reinforces the importance of updated recommendations based on scientific data. The information collected helps guide food policies, especially for pregnant women, children and consumers with intensive fish habits.
The research was funded by the Foundation for Science and Technology (FCT) and included the collaboration of scientists from the University of Aveiro.
The joint work sought to deepen knowledge about the balance between the nutritional benefits of fish and the potential risks associated with natural contaminants.
Experts’ conclusion
The final message is clear: eating fish continues to be healthy and recommended. The choice of species, the size of the specimen and the frequency of consumption are decisive factors in maintaining a balanced diet. Moderation and variety continue to be the most effective tools for reducing risks and enjoying all the benefits of fish.
Also read:
