The healthiest seafood to eat includes oily fish such as salmon, mackerel, sardines, and herring, which provide essential omega-3 fatty acids for heart and brain health, alongside white fish like cod and haddock for lean protein, and shellfish rich in vital minerals. Seafood offers a unique nutritional profile combining high-quality protein, vitamin D, iodine, selenium, and beneficial fats, whilst remaining low in saturated fat. The NHS recommends at least two portions of fish weekly, including one oily variety, to support cardiovascular health, cognitive function, and overall wellbeing. This guide explores the nutritional benefits, safety considerations, and sustainable choices to help you make informed decisions about incorporating seafood into a balanced UK diet.

What Makes Seafood a Healthy Choice?

Seafood represents one of the most nutrient-dense food groups available, offering a unique combination of high-quality protein, essential vitamins, minerals, and beneficial fatty acids. Unlike many terrestrial protein sources, fish and shellfish are naturally low in saturated fat whilst providing substantial amounts of omega-3 polyunsaturated fatty acids, which are associated with cardiovascular health, cognitive function, and inflammatory regulation.

The nutritional profile of seafood extends beyond macronutrients. Fish and shellfish are excellent sources of vitamin D, a nutrient often deficient in UK populations due to limited sunlight exposure, particularly during winter months. They also provide significant amounts of iodine, essential for thyroid function, and selenium, an important antioxidant mineral. Oily fish varieties additionally contain B vitamins, including B12, which is particularly important for vegetarians who occasionally include fish in their diet.

From a public health perspective, regular seafood consumption has been associated with reduced risk of coronary heart disease, stroke, and age-related cognitive decline. The NHS and British Heart Foundation both recognise seafood as a recommended component of a balanced diet. The lean protein content supports muscle maintenance and satiety, whilst the micronutrient density makes seafood particularly valuable for vulnerable groups including pregnant women, children, and older adults.

Compared to red and processed meats, seafood generally presents a more favourable health profile when consumed as part of a varied diet. The combination of easily digestible protein, beneficial fats, and essential micronutrients positions seafood as a valuable component of dietary patterns associated with longevity and reduced chronic disease risk.

Nutritional Benefits of Different Types of Seafood

Seafood encompasses a diverse range of species, each offering distinct nutritional advantages. Oily fish such as salmon, mackerel, sardines, and herring are particularly valued for their high omega-3 fatty acid content, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A 140g portion of farmed Atlantic salmon provides approximately 1.6-2.7g of omega-3s, contributing significantly to recommended intake for cardiovascular health. These species also deliver significant amounts of vitamin D, with mackerel and sardines being among the richest natural dietary sources.

White fish including cod, haddock, plaice, and sea bass offer a different nutritional profile. Whilst lower in omega-3 fatty acids compared to oily varieties, white fish are exceptionally lean, providing high-quality protein with minimal fat content. A typical portion contains approximately 25-30g of protein with less than 2g of fat, making these species particularly suitable for individuals managing their calorie intake or following low-fat dietary patterns. White fish remain good sources of iodine, selenium, and B vitamins.

Shellfish present another nutritionally distinct category. Prawns, mussels, oysters, and crab are notably rich in minerals, with oysters being one of nature's most concentrated sources of zinc, essential for immune function and wound healing. Mussels provide exceptional amounts of vitamin B12, iron, and selenium. Prawns, whilst containing dietary cholesterol, have minimal saturated fat (which has more impact on blood cholesterol levels) and provide useful amounts of phosphorus and copper.

Canned fish such as sardines, pilchards, and salmon (particularly when bones are included) offer the additional benefit of highly bioavailable calcium, supporting bone health. The canning process softens bones, making them edible and providing calcium levels comparable to dairy products. These convenient options retain most of the nutritional benefits of fresh fish whilst offering extended shelf life and affordability. When choosing canned or smoked fish, look for lower-salt options where possible.

Omega-3 Rich Fish: Top Options for Heart and Brain Health

Omega-3 fatty acids, particularly EPA and DHA, are essential nutrients that the body cannot synthesise efficiently, making dietary intake crucial. These long-chain polyunsaturated fatty acids have been associated with several cardiovascular effects, with the strongest evidence for reducing triglyceride levels, with possible small effects on blood pressure and inflammation. The British Heart Foundation recommends consuming at least one portion of oily fish weekly to support cardiovascular health.

Salmon stands as one of the most accessible and popular omega-3 rich options in the UK. Both wild and farmed Atlantic salmon provide omega-3s, though levels vary depending on diet and species. A 140g portion delivers approximately 1.6-2.7g of combined EPA and DHA. Salmon also provides high-quality protein, B vitamins, and potassium. Mackerel offers high omega-3 concentrations, with similar portion sizes providing approximately 2-3g of these beneficial fats. Atlantic mackerel is widely available in UK waters and represents an economical choice.

Sardines and pilchards (the same species at different life stages) are nutritional powerhouses, offering good omega-3 content alongside calcium when consumed with bones. Fresh, frozen, or canned varieties all retain significant nutritional value. Herring, another oily fish abundant in UK waters, provides comparable omega-3 levels to mackerel and is traditionally consumed fresh, pickled, or smoked (though smoked varieties contain higher sodium levels).

Trout, particularly rainbow trout farmed in the UK, offers a milder-flavoured alternative with good omega-3 content. Anchovies, whilst typically consumed in smaller quantities, are rich in omega-3s per gram and add nutritional value when used in cooking or as toppings. For optimal brain health benefits, particularly during pregnancy and early childhood, regular consumption of these omega-3 rich species supports neurodevelopment and cognitive function throughout life. The NHS recommends pregnant women consume up to two portions of oily fish weekly (but no more), whilst observing specific safety guidelines regarding certain species. Importantly, tuna does not count as an oily fish portion during pregnancy.

Mercury Levels and Safety Considerations in Seafood

Mercury contamination represents the primary safety concern associated with seafood consumption. Mercury exists in aquatic environments as methylmercury, a neurotoxic compound that bioaccumulates in fish tissue and biomagnifies up the food chain. Larger, longer-lived predatory species accumulate higher mercury concentrations, whilst smaller, shorter-lived fish generally contain minimal levels. The Food Standards Agency (FSA) and NHS provide specific guidance to protect vulnerable populations, particularly pregnant women, women planning pregnancy, and young children.

High-mercury fish that should be limited include shark, swordfish, and marlin. The NHS advises pregnant women and children to avoid these species entirely, while other adults should limit consumption to no more than one portion per week. Tuna requires particular attention: fresh tuna steaks contain moderate mercury levels, and pregnant women should limit consumption to no more than two steaks weekly. Canned tuna contains lower mercury levels due to the smaller species used, though pregnant women should still limit intake to no more than four medium cans weekly. Importantly, tuna does not count as an oily fish portion during pregnancy.

For the general adult population, the health benefits of regular seafood consumption substantially outweigh mercury-related risks when following NHS guidance. Lower-mercury options include salmon, mackerel, sardines, trout, herring, prawns, cod, haddock, and plaice. These species can be consumed regularly within recommended limits. The NHS recommends adults eat at least two portions of fish weekly, including one oily variety.

Beyond mercury, other considerations include allergic reactions to fish or shellfish, which can be severe. If you experience breathing difficulties, throat swelling, or dizziness after consuming seafood, call 999 immediately as these are signs of anaphylaxis. For less severe reactions, contact NHS 111 for advice. Listeria is another concern, particularly for pregnant women and those with weakened immune systems, who should avoid ready-to-eat smoked fish unless thoroughly heated until steaming hot. Histamine poisoning (scombroid) can occur from improperly stored oily fish. Ensuring seafood is purchased from reputable sources, stored correctly, and consumed fresh minimises this risk. If you take anticoagulant medications and are considering high-dose fish oil supplements (not typical dietary fish), consult your healthcare provider first, as these may affect medication efficacy.

Sustainable Seafood Choices in the UK

Sustainability considerations are increasingly important when selecting seafood, as overfishing and destructive fishing practices threaten marine ecosystems and long-term food security. The Marine Conservation Society (MCS) provides comprehensive guidance through their Good Fish Guide, rating seafood based on stock health, fishing methods, and management practices. Making informed choices supports both environmental conservation and the future availability of healthy seafood options.

More sustainable options in the UK often include mackerel from the North East Atlantic (when caught using handlines or other sustainable methods), herring from well-managed North Sea stocks, and mussels and oysters from rope-grown or farmed sources (which can actually improve water quality). Sardines and pilchards from Cornwall may represent good options. Alaska pollock from MSC-certified fisheries can serve as an alternative to cod in many recipes, as these stocks are generally better managed.

Species to approach with caution include certain cod stocks (though Icelandic and North East Arctic cod may be better choices), bluefin tuna (which has faced significant overfishing), and tropical prawns caught using methods that can damage seabed habitats. Skate and ray species are often vulnerable to overfishing. When purchasing, look for Marine Stewardship Council (MSC) certification, which indicates seafood from independently assessed fisheries. The Aquaculture Stewardship Council (ASC) label identifies responsibly farmed seafood.

UK consumers can support sustainability by choosing locally caught fish when available, which reduces transportation emissions and supports domestic fishing communities. Seasonal eating aligns with natural abundance patterns. Diversifying seafood choices beyond the most popular species (salmon, cod, tuna, prawns) reduces pressure on heavily exploited stocks. Retailers including major supermarkets increasingly provide sustainability information on packaging. The MCS Good Fish Guide app offers convenient, up-to-date ratings when shopping. As sustainability ratings change regularly based on stock assessments and fishing practices, checking current MCS ratings is recommended for the most accurate guidance.

How Often Should You Eat Seafood? NHS Recommendations

The NHS provides clear, evidence-based guidance on seafood consumption frequency to optimise health benefits whilst minimising potential risks. The cornerstone recommendation advises adults to consume at least two portions of fish per week, with each portion weighing approximately 140g when cooked (or 170g raw). Crucially, one of these two portions should be oily fish such as salmon, mackerel, sardines, or trout to ensure adequate omega-3 fatty acid intake for cardiovascular and cognitive health.

For pregnant women, women planning pregnancy, and breastfeeding women, the guidance remains two portions of fish weekly, including one oily fish, but with specific restrictions. They should avoid high-mercury species (shark, swordfish, marlin) entirely, limit oily fish to no more than two portions weekly, and limit tuna consumption to no more than two fresh tuna steaks or four medium cans of tuna weekly. Importantly, tuna does not count as an oily fish portion during pregnancy. These precautions protect foetal neurodevelopment, as methylmercury can cross the placental barrier. Despite these restrictions, the NHS emphasises that the nutritional benefits of appropriate seafood consumption during pregnancy—particularly omega-3s for brain development—are substantial and should not be avoided entirely.

Children can begin eating fish from weaning age, with portions adjusted according to age and appetite. Young children should avoid high-mercury species, and bones should be carefully removed to prevent choking hazards. Girls should follow the same oily fish limits as women (no more than two portions weekly), while boys and men can safely consume up to four portions of oily fish weekly if desired, as they face lower mercury-related risks. However, there is no official recommendation to exceed two portions weekly for general health maintenance.

For individuals who do not consume fish, whether due to dietary preferences, allergies, or cultural reasons, alternative omega-3 sources include algae-based supplements (providing EPA and DHA directly), flaxseeds, chia seeds, and walnuts (providing ALA, though conversion to EPA and DHA is limited). If you have specific health conditions, take medications that may interact with omega-3s, or have concerns about appropriate seafood intake for your circumstances, consult your GP or a registered dietitian for personalised advice. If you experience any suspected side effects from fish oil supplements, report them through the MHRA Yellow Card scheme.

Frequently Asked Questions