What is the healthiest shellfish you can eat?

The ocean provides an incredible array of lean proteins, and among its treasures, shellfish often stand out for their dense nutritional packages. These aquatic invertebrates—a category including crustaceans like crab and shrimp, and mollusks such as clams, oysters, and mussels—offer substantial health rewards, often with fewer calories than many land-based meats. For those aiming to meet the general recommendation of consuming at least two servings of seafood weekly, where one is oily fish, shellfish can play a vital role in achieving nutrient targets like protein, Vitamin B12, zinc, and selenium.

# Nutrient Powerhouse

Seafood in general delivers crucial components frequently lacking in modern diets, including protein, Vitamin D, B12, iron, selenium, and zinc. Shellfish, specifically, are noteworthy because they are typically low in fat. This low-fat profile makes them advantageous choices when compared to fattier fin fish or red meat, such as the comparison showing blue crabs having only 90 calories per 3 oz serving versus Mackerel at 190 calories or steak at up to 230 calories. While they may not reach the sheer concentration of long-chain omega-3 fatty acids (EPA and DHA) found in oily fish like salmon, certain shellfish still contribute these heart-healthy fats. Mussels, oysters, squid, and crab all offer these essential fatty acids, though often at lower levels than the richest fish sources.

# Bivalve Super Source

Focusing on mollusks reveals some of the most nutrient-dense options available. Clams, for example, are recognized for being low in mercury while delivering an almost unbelievable amount of Vitamin B12—a single 3-ounce serving can cover over 3,000% of the daily value. This extreme concentration makes clams a necessary consideration for anyone looking to boost B12, which is essential for red blood cell function and healthy nerve cell behavior. While other excellent sources like salmon provide around 196% of the DV for B12 in a similar serving size, the sheer volume found in clams places them in a class of their own for this specific nutrient. Furthermore, clams are rich in zinc and selenium, both supporting the immune system.

Mussels share many of these benefits. Farmed mussels are frequently highlighted not just for their nutrition but also for their environmental profile; swapping beef for farmed mussels can noticeably reduce an individual’s carbon footprint, as mussels are associated with far lower greenhouse gas emissions. Nutritionally, mussels are robust providers of protein, offering nearly 24 grams per 100-gram serving, only slightly less than the protein found in ground beef. They are also a good source of B12 and iron.

# Mineral Richness

When looking specifically at essential trace minerals, oysters and scallops emerge as strong contenders. Oysters are calorie-low but pack a high protein punch, offering nearly 22 grams in a 3-ounce portion while clocking in at just 126 calories. Beyond protein and omega-3s, oysters provide over 100% of the daily needs for B12, zinc, and copper, alongside over 50% of the necessary selenium, making them particularly beneficial for those needing increased iron intake. Copper is necessary for red blood cell production, and zinc supports immune function, taste, smell, and wound healing.

Scallops also score highly for lean protein, and their amino acid profile is interesting. They contain taurine and glycine, compounds that research suggests may offer protection against atherosclerosis—the hardening or plaque buildup in arteries that leads to heart disease. Like clams, scallops generally maintain a low mercury profile and deliver significant amounts of B12, zinc, and selenium.

# Crustacean Benefits

The crustacean family also offers worthy additions to a healthy diet. Shrimp owes its distinctive pink color to astaxanthin, an antioxidant whose activity has been shown to be up to 500 times greater than that of Vitamin E. Beyond this powerful compound, shrimp provides necessary B12, selenium, zinc, and quality protein. Crab meat is similarly rich, with cooked blue crab providing about 29% of the daily zinc requirement per 3-ounce serving, in addition to B vitamins and heart-protective omega-3 fats. It is worth noting that while white crab meat is recommended without limit, regular consumption of brown crab meat should be limited for those who eat fish often. Lobster, beloved for its texture, is also a nutritional standout, offering over 16 grams of protein and high percentages of zinc and selenium in a 3-ounce serving, along with B12 and copper.

# The Shadow of Contaminants

While the nutritional breakdown is impressive, no discussion of shellfish health is complete without addressing the environmental challenges they face. Because many popular shellfish, like oysters and mussels, are filter feeders, they naturally concentrate whatever is in their water, which creates a dual risk: heavy metals and man-made pollution.

One major concern centers on mercury. Mercury is a heavy metal that accumulates in the body over time and can pose risks, especially to developing fetuses and young children. Fortunately, the consensus suggests that most shellfish—oysters, clams, and mussels being explicitly named—are low in mercury compared to larger, older predatory fish. However, this is a generalization, and responsible sourcing remains paramount. For instance, while many fin fish have strict weekly limits, the NHS advises that generally, there are no maximum limits placed on most shellfish consumption due to mercury concerns, with the notable exception being brown meat from crabs, which should be eaten less frequently.

Microplastics present a newer, more pervasive worry. As filter feeders process vast amounts of water, they ingest tiny plastic fragments suspended in the marine environment. Experts have noted that anthropomorphic debris, primarily plastic fibers, is found in the digestive tracts of many sampled shellfish. These microplastics are absorbed through the gastrointestinal tract, and researchers suggest they might trigger inflammation or cellular damage, although the full scope of the long-term public health impact requires more study.

In practical terms for the consumer, this means that while the inherent nutrients are high, the safety of that nutrient package depends heavily on where the shellfish came from. If you are eating shellfish raw, such as oysters, this risk is amplified for viruses and bacteria like norovirus, which cooking does not eliminate.

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# Safety Check

Beyond chemical accumulation, the immediate risk of foodborne illness from shellfish is significant. Mollusks, in particular, are notorious for absorbing bacteria and viruses from their surrounding waters. The key here is thorough cooking, as this process kills viruses and bacteria. Shucked shellfish like clams, mussels, and oysters are fully cooked when they become plump and opaque, and their shells will open. A critical safety step is never to eat a clam or mussel that remains closed after cooking; it signals the organism died before cooking, making it unsafe.

This need for thorough cooking leads to an important consideration regarding chemical versus biological contaminants. Cooking will eliminate the risks associated with bacteria and parasites, but it will not break down naturally occurring shellfish toxins or heavy metals like mercury. Therefore, consumers need a two-pronged safety approach: ensure cooking protocols kill pathogens, and ensure sourcing protocols minimize chemical exposure. Given that certain toxins do not degrade when heated, sourcing shellfish from waters known to be tested and cleared for harvest is non-negotiable, especially for vulnerable populations.

# Sustainable Choices

Ensuring that shellfish remains a healthy option for future generations means actively choosing sustainably sourced options. Overfishing and destructive practices put immense pressure on marine ecosystems. The Monterey Bay Aquarium Seafood Watch program uses a traffic light system to guide consumers toward environmentally sound choices.

Shellfish generally fare very well in these assessments because many—particularly farmed bivalves—are considered "green" or "Best Choice" options. Farmed clams, oysters, and mussels are often celebrated because their cultivation can even enhance biodiversity and help restore coastal areas. For instance, farmed mussels are specifically called out as a great choice that is both nutritious and environmentally positive compared to high-emission animal proteins like beef. When you choose seafood rated Green by programs like Seafood Watch, you are selecting items that are well-managed and do not cause undue harm to other species or the surrounding environment. Eating a wide variety of seafood also helps ensure that specific stocks are not depleted by over-demand.

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# Preparation Matters

How you prepare your shellfish significantly impacts how healthy the final meal is. Health authorities consistently recommend avoiding fried preparation methods. Frying adds unnecessary fat and calories, and more concerningly, it can create harmful compounds such as heterocyclic amines (HCAs) and aldehydes, which have been linked to increased health risks, including cancer.

The healthiest methods for preparing shellfish, just as with fin fish, are baking, grilling, or steaming. These methods preserve the lean protein and essential nutrients without loading the dish with unhealthy added fats. When cooking shellfish like scallops, knowing the visual cues is simpler than timing an internal thermometer reading: they become milky white and firm. For shrimp, which turn pink and firm, a quick cook time is key.

If you are incorporating shellfish regularly, remember that this food group is best served as part of a broader, well-rounded diet rich in fruits, vegetables, nuts, and beans, helping to round out the overall nutritional intake alongside the protein and minerals gained from the sea. The health benefits of seafood—reduced risk of heart disease, improved cognition—are maximized when eating is part of a consistent, quality pattern, not an isolated event. If one chooses clams or oysters regularly for their mineral density, balancing those meals with oily fish ensures a sufficient intake of those heart-protective, long-chain omega-3s that are slightly less concentrated in bivalves compared to fish like salmon.