Mercury in cod: is it high or low? (compared to other fish)

What levels of mercury does cod actually contain?

Cod is considered one of the fish with moderate to low mercury concentrations , placing it in an intermediate category that makes it a relatively safe option for regular consumption. The levels of this heavy metal in cod typically range between 0.10 and 0.40 parts per million (ppm), depending on multiple factors such as origin, size of the fish, and environmental habitat conditions.

This concentration places cod well below predatory species such as bluefin tuna or swordfish, which can reach levels exceeding 1.0 ppm. However, it is not in the category of fish with minimal mercury content, such as sardines or Cantabrian anchovies.

Cod from colder, pristine waters, such as those off the coasts of Iceland and Norway, tend to have slightly lower mercury concentrations due to less industrial pollution in these Arctic ecosystems. This geographical difference is particularly relevant for consumers seeking to minimize their mercury exposure without sacrificing the exceptional nutritional properties of this white fish.

Detailed comparison: cod versus other popular fish

Cod versus tuna: significant differences in mercury

The disparity in mercury levels between cod and different varieties of tuna is considerable. While cod maintains average concentrations of 0.10-0.40 ppm, tuna exhibits a much wider range depending on the specific species.

Canned albacore tuna contains approximately 0.32 ppm, placing it at the upper end of the range for cod. However, fresh bluefin tuna can reach concentrations of 1.0 ppm or higher, tripling the typical levels found in cod. This difference is primarily due to body size and position in the food chain: tuna are larger apex predators that bioaccumulate mercury over their longer lifespan.

Cod versus salmon: a comparative mercurial analysis

Salmon emerges as the clear winner in terms of low mercury levels, with average concentrations of 0.01–0.05 ppm, significantly lower than cod. This advantage of salmon is attributed to its diet, based primarily on small crustaceans, and its relatively short life cycle compared to other fish of similar size.

However, cod compensates for this mercury disadvantage with other distinctive nutritional characteristics: higher protein content per serving, less saturated fat, and a more complete essential amino acid profile. The choice between the two fish should consider not only mercury content but also the overall nutritional context and individual culinary preferences.

Factors that influence the mercury concentration in cod

The accumulation of mercury in cod is not a uniform phenomenon, but rather responds to a complex interaction of environmental, biological and geographical variables that determine the final levels present in muscle tissue.

Size and age are determining factors: larger and longer-lived specimens tend to accumulate higher levels of mercury due to the process of progressive bioaccumulation. A 5-year-old cod will typically have lower concentrations than a 15-year-old specimen from the same region.

Geographic origin has a decisive influence. The waters of the North Atlantic, particularly around Iceland and the Norwegian coast, maintain considerably lower levels of mercury contamination than other, more industrialized fishing regions. This difference translates directly into the sanitary quality of the final product.

The specific feeding patterns of each cod population also modulate mercury uptake. Populations that feed primarily on benthic invertebrates exhibit lower concentrations than those with diets based on small fish, which have already begun the bioaccumulation process.

Fish recommended for their low mercury content

For consumers particularly sensitive to mercury exposure, there is a selection of marine species that combine excellent nutritional properties with minimal concentrations of this heavy metal.

• Sardines: 0.01-0.05 ppm, rich in omega-3 and calcium
• Cantabrian anchovies: 0.02-0.04 ppm, exceptional in flavor and tradition
• Atlantic salmon: 0.01-0.05 ppm, premium source of essential fatty acids
• Hake: 0.05-0.25 ppm, a versatile and mild white fish
• Sole: 0.03-0.15 ppm, delicate texture and refined flavor
• Sea bass: 0.10-0.30 ppm, ideal for gourmet preparations

These species represent safe alternatives that allow maintaining a diet rich in fish without compromising the safety limits established by international health authorities.

Specific recommendations for pregnancy and children

During pregnancy and breastfeeding, nutritional needs increase while tolerance to certain contaminants decreases. Cod, with its moderate mercury levels, requires a balanced approach that maximizes its nutritional benefits while minimizing potential risks.

Health authorities recommend that pregnant women and young children limit their consumption of cod to 2-3 servings per week, approximately 100-150 grams each. This frequency allows them to benefit from its exceptional protein content, B vitamins, and essential minerals without exceeding safe mercury levels.

For children under 3 years old, the recommended serving size is reduced to 50-75 grams per portion, maintaining a frequency of 2-3 times per week. It is crucial to alternate cod with species that have lower mercury content, such as sardines or anchovies, to diversify exposure and optimize the overall nutritional profile.

Quality signals that minimize risks

Selecting top-quality cod not only guarantees an exceptional dining experience but also helps minimize exposure to contaminants like mercury. Specimens from sustainable fisheries and less polluted waters invariably have better health profiles.

Artisanal cod, desalted and processed using traditional techniques, better retains its original nutritional properties while facilitating the removal of any surface residue. Vacuum packaging and a continuous cold chain preserve the product's integrity from catch to final consumption.

Full traceability, which includes information on catch area, processing date and preservation methods, allows consumers to make informed decisions based on objective food quality and safety criteria.

Nutritional benefits that compensate for the moderate presence of mercury

Despite containing moderate levels of mercury, cod offers such an exceptional nutritional profile that the benefits far outweigh the risks when consumed within the recommended frequencies.

Its protein content reaches 20-25% of its total weight, providing all the essential amino acids in optimal proportions for human protein synthesis. This characteristic is particularly valuable during growth, pregnancy, and recovery from illness.

Cod is an exceptional source of vitamin B12, essential for red blood cell formation and the proper functioning of the nervous system. A 150-gram serving provides more than 200% of the daily requirement for this vitamin, which is especially crucial for people following meat-restricted diets.

Its selenium content acts as a natural antioxidant, partially counteracting the oxidative effects of mercury and other environmental pollutants. This endogenous protective effect represents an additional defense mechanism that reinforces the safety of moderate consumption.