Cod is widely recognised as a low-mercury fish, making it one of the safest seafood choices for regular consumption across all age groups. Mercury accumulates in fish through biomagnification, with larger predatory species containing significantly higher levels than smaller fish like cod. According to the Food Standards Agency (FSA) and European Food Safety Authority (EFSA), Atlantic and Pacific cod typically contain mercury levels well below regulatory limits—usually between 0.05 to 0.15 mg/kg compared to the maximum permitted 0.5 mg/kg. This positions cod alongside salmon, haddock, and plaice as an excellent option for those seeking the nutritional benefits of fish whilst minimising mercury exposure.

Mercury Levels in Cod: What the Evidence Shows

Cod is generally considered a low-mercury fish, making it one of the safer seafood choices for regular consumption. Mercury accumulates in fish through a process called biomagnification, where smaller organisms absorb mercury from contaminated water, and larger predatory fish accumulate higher concentrations by consuming these smaller fish throughout their lifespan. Cod, being a relatively small to medium-sized fish with a shorter lifespan compared to apex predators, accumulates significantly less mercury.

According to data from the Food Standards Agency (FSA) and European Food Safety Authority (EFSA) monitoring programmes, Atlantic cod (Gadus morhua) and Pacific cod (Gadus macrocephalus) typically contain mercury levels well below the maximum limits set by UK and European regulatory bodies. Under retained EU Regulation (EC) No 1881/2006, the maximum permitted level is 0.5 mg/kg for most fish species, and cod consistently falls well beneath this threshold, typically measuring between 0.05 to 0.15 mg/kg.

The mercury present in fish exists primarily as methylmercury, an organic form that is readily absorbed by the human gastrointestinal tract and can cross both the blood-brain barrier and the placenta. However, the low concentrations found in cod mean that the health risks associated with mercury exposure are minimal for most people consuming cod as part of a balanced diet. Regular monitoring by UK authorities ensures that commercially available cod meets safety standards, providing consumers with confidence in their seafood choices.

How Cod Compares to Other Fish for Mercury Content

When comparing mercury content across different fish species, cod ranks favourably among the lowest-mercury options available. This positions it alongside other popular choices such as salmon, haddock, plaice, and sardines. Understanding these comparisons helps consumers make informed decisions about their seafood consumption.

Low-mercury fish (similar to cod):

• Haddock

• Pollock

• Coley (saithe)

• Plaice and sole

• Salmon (farmed and wild)

• Trout

• Sardines and anchovies

• Canned tuna (lower mercury than fresh tuna)

Medium-mercury fish (higher than cod):

• Sea bass

• Sea bream

• Halibut

• Monkfish

• Fresh tuna steaks

High-mercury fish (significantly higher than cod):

• Swordfish

• Marlin

• Shark

The substantial difference in mercury levels relates to several factors, including the fish's position in the food chain, lifespan, size, and feeding habits. Predatory fish such as swordfish and marlin can contain mercury levels 10 to 20 times higher than cod because they consume numerous smaller fish over their extended lifespans, which can span several decades. Cod, conversely, feeds primarily on smaller fish, crustaceans, and molluscs, and typically lives for 10 to 15 years, limiting mercury accumulation.

According to NHS and FSA guidance, adults should limit consumption of high-mercury fish (shark, swordfish, and marlin) to one portion per week, while pregnant women and children should avoid these entirely. This makes cod an excellent choice for those seeking the nutritional benefits of fish whilst minimising mercury exposure.

Safe Consumption Guidelines for Cod in the UK

The NHS and Food Standards Agency provide clear guidance on fish consumption that applies to cod and other low-mercury species. For the general adult population, there are no specific restrictions on cod consumption due to its low mercury content. Adults are encouraged to eat at least two portions of fish per week, including one portion of oily fish, as part of a healthy, balanced diet. Cod, being a white fish, can be consumed more frequently without concern.

A standard portion of fish is considered to be approximately 140 grams when cooked, or roughly 170 grams raw, according to NHS guidance. This equates to a piece about the size of an adult's hand. Because cod contains minimal mercury, adults can safely consume it several times per week if desired, though dietary variety remains important for obtaining a broad spectrum of nutrients.

For vulnerable groups including pregnant women, women trying to conceive, breastfeeding mothers, and young children, the FSA specifically identifies cod as a safe choice. These groups should:

• Avoid high-mercury fish entirely (shark, swordfish, and marlin)

• Limit fresh tuna to 2 steaks per week or 4 medium-sized cans per week (due to mercury content)

• Limit oily fish to 2 portions per week (due to pollutants other than mercury)

• Cod and other white fish can be eaten freely

When preparing cod, cooking methods can influence its nutritional value. Healthier preparation methods include:

• Baking or roasting

• Grilling

• Steaming

• Poaching

These methods preserve the fish's nutritional benefits whilst avoiding the addition of excessive fats. Breaded and deep-fried preparations, whilst popular, add significant calories and should be consumed less frequently as part of an overall healthy eating pattern.

Health Benefits of Eating Cod Despite Mercury Concerns

Cod offers substantial nutritional benefits that far outweigh the minimal mercury concerns for most consumers. As a lean protein source, cod provides approximately 20 grams of high-quality protein per 100-gram serving whilst remaining very low in fat (less than 1 gram) and calories (approximately 80-90 calories per 100 grams), according to McCance and Widdowson's The Composition of Foods Integrated Dataset. This makes it an excellent choice for those managing their weight or seeking to increase protein intake without excess calories.

The protein in cod contains all essential amino acids required for tissue repair, immune function, and the production of enzymes and hormones. This complete protein profile supports muscle maintenance, particularly important for older adults at risk of sarcopenia (age-related muscle loss).

Key micronutrients in cod include:

• Vitamin B12: Essential for neurological function, red blood cell formation, and DNA synthesis. A serving typically provides a significant proportion (around 50-100% of the adult Reference Nutrient Intake per 100g, depending on preparation).

• Iodine: Critical for thyroid hormone production and metabolic regulation. Cod is one of the richest dietary sources of iodine.

• Selenium: An important antioxidant that supports immune function and thyroid health.

• Phosphorus: Necessary for bone health and energy metabolism.

• Vitamin B6 and niacin: Support energy production and nervous system function.

Whilst cod is not an oily fish and therefore contains lower levels of omega-3 fatty acids compared to salmon or mackerel, it still provides some beneficial EPA and DHA. The Scientific Advisory Committee on Nutrition (SACN) and other UK health bodies note that populations consuming fish regularly have lower rates of coronary heart disease and stroke. For most individuals, the proven health benefits of consuming low-mercury fish like cod substantially exceed any theoretical risks from trace mercury exposure.

Who Should Limit Cod Intake: Pregnancy and Children

Despite cod's low mercury content, understanding specific guidance for vulnerable populations ensures optimal safety. Pregnant and breastfeeding women can safely consume cod without restriction, as it falls into the lowest mercury category. The NHS and FSA advise that these groups can eat cod and other white fish as often as they like, while aiming for at least two portions of fish weekly overall. However, they should:

• Avoid shark, swordfish and marlin completely (due to high mercury)

• Limit tuna to no more than 2 fresh steaks or 4 medium-sized cans per week

• Limit oily fish to no more than 2 portions per week

The high-quality protein, iodine, and vitamin B12 in cod support foetal development, particularly brain and nervous system formation.

Pregnant women should ensure cod is thoroughly cooked until steaming hot throughout, opaque and flaking easily to eliminate any risk of foodborne pathogens such as Listeria monocytogenes. The FSA advises that vulnerable groups (including pregnant women) should avoid ready-to-eat cold-smoked fish products unless thoroughly cooked, to minimise infection risk.

Children and infants can safely consume cod from the time solid foods are introduced, typically around six months of age. The NHS advises that children should avoid shark, swordfish and marlin completely. Fish provides nutrients crucial for growth and cognitive development, and establishing fish consumption habits early may promote lifelong healthy eating patterns. Parents should ensure fish is boneless and appropriately textured for the child's developmental stage to prevent choking hazards.

The only groups who might consider limiting overall fish intake (though not specifically cod) are those with fish allergies or specific medical conditions requiring dietary modifications. Individuals taking certain medications should follow their healthcare provider's advice about diet consistency.

If you have specific health conditions or concerns about incorporating fish into your diet or your child's diet, consult your GP or a registered dietitian for personalised advice. For most people, cod represents one of the safest and most nutritious seafood choices available, suitable for frequent consumption across all life stages.

Frequently Asked Questions