Clams: Nutrition Facts, Health Benefits, and the Most Vitamin B12-Dense Food You Can Eat

There is a single nutritional statistic about clams that makes most people read it twice: 4,120% of the daily Vitamin B12 requirement per 100g. Not 412%. Not 41 percent of the daily requirement. Forty-one times the daily requirement. In 148 calories.

Clams are the most concentrated source of Vitamin B12 available from any commonly eaten food — even more than beef liver, which is itself legendary for its B12 content. They are also outstanding for selenium (116% DV), copper (77% DV), manganese (43% DV), and phosphorus (27% DV), provide 628mg of potassium, useful iron, and even 25% of daily vitamin C, and deliver 25.6g of complete protein at just 148 calories — a protein-to-calorie ratio close to chicken breast.

Clams are chronically underrated in Western fitness and nutrition culture — associated in many people’s minds with seafood platters rather than performance nutrition. That is a significant oversight. Clam nutrition is genuinely extraordinary across many of the metrics that matter.

Clams Nutrition Facts (per 100g, cooked)

Clams Nutrition Facts (per 85g serving — approximately 9–10 small clams)

A standard serving of cooked clams is approximately 85g of clam meat:

Vitamins in Clams (per 100g, cooked)

USDA has no values for vitamins D, E, or K in cooked clams. % Daily Values use the FDA’s current Daily Values.

Standout: The 4,120% daily value of Vitamin B12 per 100g of cooked clams is not only the highest in our nutrition facts collection — it is one of the highest B12 concentrations of any commonly eaten food. For context: the daily value for B12 is 2.4µg. A 100g serving of clams provides 98.9µg — over 41 days’ worth on paper, although the body absorbs only a small fraction of a large dose at once (more on that below). Regular clam meals still make a substantial contribution to B12 status. Clams are also a notable source of riboflavin (33% DV) and, unusually for an animal food, vitamin C (25% DV).

Minerals in Clams (per 100g, cooked)

Multiple standouts: Clams are a genuinely strong mineral source:

Selenium at 116% DV — exceeding the full daily selenium requirement per 100g. Selenium is essential for glutathione peroxidase antioxidant function and thyroid hormone activation, and clams are one of the richest selenium sources available.

Copper at 77% DV — copper supports iron metabolism and red blood cell formation, connective tissue, and the antioxidant enzyme superoxide dismutase.

Iron at 16% DV — a useful contribution, though far lower than the figures widely quoted online (see the iron section below).

Phosphorus at 27% DV for energy production and bone health.

Potassium at 628mg (13% DV) — a meaningful contribution to the potassium intake that manages blood pressure and supports muscle function.

Zinc at 25% DV — supporting immune function, testosterone production, and protein synthesis.

The B12 Story: Why 4,120% Is Not a Mistake

The Vitamin B12 figure in clams is so far beyond any reasonable daily requirement that it naturally prompts the question of whether it’s accurate. It is — and understanding why clams contain such extraordinary B12 concentrations explains both the biology and the practical nutritional implications.

Why Clams Concentrate B12

Vitamin B12 is produced exclusively by bacteria and archaea — no plant or animal synthesizes it independently. In the marine food chain, B12 is produced by bacteria in ocean sediments and seawater. Clams — as filter feeders that continuously pump seawater through their bodies to extract nutrients — accumulate B12 from the marine bacteria and plankton they filter and consume over their lifetime.

Clams concentrate B12 in their tissues far beyond what their own metabolic requirements would dictate, making them one of the most extreme natural examples of biological nutrient concentration.

Other bivalves use the same filter-feeding mechanism — oysters and mussels have exceptional B12 too (roughly 7–10 times the daily value per 100g, cooked), though nothing like clams, while scallops have far less.

Why This Extraordinary B12 Matters

B12 deficiency is common. Vitamin B12 deficiency is one of the most prevalent nutritional deficiencies globally — particularly in:

• Older adults: stomach acid production declines with age, making it harder to release B12 from food so it can be absorbed
• Vegetarians and vegans: B12 is found naturally almost only in animal foods
• People taking metformin (common diabetes medication): metformin impairs B12 absorption
• People with pernicious anaemia: autoimmune destruction of the stomach cells that make intrinsic factor, the protein needed to absorb B12
• Anyone with gastrointestinal conditions affecting absorption

B12 deficiency causes serious, potentially irreversible harm. Unlike most nutritional deficiencies that manifest with fatigue and general malaise, B12 deficiency causes progressive neurological damage — peripheral neuropathy (tingling and numbness in hands and feet), cognitive decline, memory impairment, and eventually irreversible neuronal damage if untreated.

Clams as a B12 food. The body can only absorb a few micrograms of B12 from a single meal, so most of the 84µg in an 85g serving passes through unabsorbed — but even so, a serving of clams covers well over a day’s needs, and B12 stored in the liver can last for years. One important caveat: people whose deficiency comes from an absorption problem (pernicious anaemia, low stomach acid, metformin use) often can’t absorb enough B12 from any food and need supplements or injections — clams can’t fix that kind of deficiency on their own.

What B12 Actually Does

Vitamin B12 serves several critical physiological functions:

Myelin synthesis — B12 is essential for maintaining the myelin sheath surrounding nerve fibers. Myelin acts as insulation for nerves, enabling rapid, efficient signal transmission. B12 deficiency causes demyelination — the sheath deteriorates, and nerve signals slow or misfire. This is the mechanism behind the neurological symptoms of deficiency.

DNA synthesis — B12 works with folate to produce thymidine — one of the four bases of DNA. Without adequate B12, DNA synthesis is impaired, cell division slows, and megaloblastic changes occur in rapidly dividing cells like those in bone marrow.

Red blood cell formation — megaloblastic anaemia from B12 deficiency produces large, immature red blood cells with reduced oxygen-carrying capacity. Symptoms include extreme fatigue, shortness of breath, and pale skin.

Homocysteine metabolism — B12 converts homocysteine to methionine via the methionine synthase reaction. Elevated homocysteine is associated with cardiovascular risk, though trials lowering homocysteine with B vitamins haven’t reduced heart attacks or strokes.

Cognitive health — B12 is essential for the production of neurotransmitters and the maintenance of brain cell integrity. Low B12 status is consistently associated with accelerated cognitive decline, dementia risk, and depression.

The Iron Story: Why Clam Iron Figures Vary So Much

Clams are often described as one of the richest iron sources in the human diet — many websites quote around 28mg of iron per 100g, well over the full daily value. That figure comes from older USDA data, and it once appeared in official US dietary guidance. USDA’s current figure for cooked clams is far lower: 2.8mg per 100g, or 16% of the daily value.

Laboratory analyses explain the confusion: the iron content of clam products varies enormously, from under 1mg to nearly 60mg per 100g. Chopped and minced canned clams have averaged about 1.4mg per 100g, while some canned whole baby clams have tested very high — so for canned clams, the label of the specific product is the only reliable guide.

Why This Matters for Iron Deficiency

Iron deficiency is the world’s most common nutritional deficiency and the leading cause of anaemia, which affects around 2 billion people globally. Symptoms include:

• Persistent fatigue and weakness
• Impaired cognitive function and concentration
• Reduced exercise performance and aerobic capacity
• Compromised immune function
• In children, developmental delays

For people managing iron deficiency — particularly premenopausal women, pregnant women, endurance athletes, and pescatarians — clams can contribute useful iron, especially products whose labels show a high iron content. But given how much clam iron varies, they shouldn’t be relied on as a guaranteed fix.

Iron and Vitamin C

Vitamin C boosts the absorption of non-haem iron — and unusually for an animal food, clams bring their own: 22.1mg of vitamin C per 100g (25% DV). Classic pairings like lemon juice in clam linguine or tomatoes in Manhattan clam chowder add more, and help the iron from any plant ingredients in the dish too.

Health Benefits of Clams

Neurological Health and B12 Protection

As discussed above, the 4,120% DV of B12 per 100g makes clams one of the most powerful dietary sources for supporting neurological health. Regular clam meals contribute substantially to B12 status and support the full range of B12-dependent neurological functions.

Older adults are the population most vulnerable to B12 deficiency, because food-bound B12 becomes harder to absorb with age — which is why the US National Academies advise people over 50 to get most of their B12 from fortified foods or supplements. Clams are a valuable addition to that, not a substitute for it.

Exceptional Protein Efficiency

At 25.6g of complete protein per 100g for 148 calories — about 0.17g of protein per calorie — clams come close to chicken breast (0.19g per calorie) and canned light tuna (0.21g per calorie), while bringing vastly more B12, selenium, and copper.

The protein in clams is complete — containing all 9 essential amino acids in good proportions — and has excellent bioavailability. For athletes managing calorie intake while maintaining high protein targets, clams are one of the more calorie-efficient protein sources available from any whole food.

Outstanding Selenium for Antioxidant Defence

At 116% of daily selenium per 100g, clams exceed the full daily selenium requirement in a single serving. Selenium is essential for:

Glutathione peroxidase — selenium-dependent enzymes that neutralize hydrogen peroxide and lipid peroxides throughout the body, protecting cell membranes and DNA from oxidative damage. This antioxidant system is one of the most important defenses against the oxidative stress of intense exercise, ageing, and environmental toxins.

Thyroid hormone activation — selenium is required by deiodinase enzymes that convert thyroid hormone T4 to its active T3 form. Selenium deficiency directly impairs thyroid function regardless of iodine status.

Male reproductive health — selenium is essential for sperm motility and male fertility. Selenoprotein P — one of the primary selenium-transporting proteins — preferentially delivers selenium to the testes, highlighting the importance of selenium for male reproductive function.

Immune function — selenium supports natural killer cell activity and the production of immunoglobulins — antibodies essential for adaptive immune defense.

Heart Health

Clams support cardiovascular health through multiple mechanisms:

B12 and homocysteine — as discussed, B12 helps keep homocysteine in check, though lowering homocysteine with B vitamins hasn’t been shown to prevent heart disease in trials.

Omega-3 fatty acids — clams contain 0.43g of omega-3 per 100g — modest compared with oily fish, but a contribution to dietary omega-3 balance.

Potassium — 628mg per 100g (13% DV) helps counteract sodium’s blood pressure-raising effects and supports healthy cardiac rhythm.

Very low saturated fat — at just 0.2g saturated fat per 100g, clams have an exceptionally clean fat profile for an animal protein.

Taurine — clams are one of the richest natural sources of taurine — an amino acid studied for cardiovascular benefits. Taurine supplements have modestly lowered blood pressure in some trials, and higher taurine intake has been linked with lower cardiovascular risk in population studies.

Iron for Oxygen Transport and Energy

The iron in clams — 2.8mg per 100g in USDA’s data, and more in some products — supports:

• Haemoglobin synthesis for oxygen transport in red blood cells
• Myoglobin production for oxygen storage in muscle cells
• Cytochrome enzymes in the mitochondrial electron transport chain — directly supporting cellular energy production
• Immune cell function — iron is essential for the proliferation and activity of T and B lymphocytes

For athletes with low iron — a surprisingly common condition, particularly in female endurance athletes and plant-dominant eaters — clams can be one useful part of an iron-rich diet, alongside red meat, legumes, and fortified foods.

Thyroid Function

The combination of selenium (116% DV) and iodine — found in most seafood — makes clams particularly valuable for thyroid health. The thyroid requires both iodine (to synthesize thyroid hormones T3 and T4) and selenium (to convert T4 to active T3), and seafood is one of the few food groups that provides both.

Cognitive Health

Beyond B12’s direct neurological importance, clams support brain health through additional mechanisms:

Iron for cognitive function — iron is essential for myelination of developing nerve fibers, for neurotransmitter synthesis (iron is a cofactor for tyrosine hydroxylase that produces dopamine and noradrenaline), and for mitochondrial energy production in brain cells. Iron deficiency — even without frank anaemia — can impair cognitive performance, attention, and memory.

Selenium for neuroprotection — selenoproteins in the brain protect against oxidative damage and support the antioxidant environment needed for healthy neuronal function. Selenium deficiency is associated with cognitive decline.

Taurine for neurotransmission — taurine acts as an inhibitory neuromodulator in the brain, reducing neuronal excitability; potential anxiolytic and sleep-supporting effects have been suggested, mostly from animal research.

Sustainability — A Uniquely Positive Environmental Profile

This is an important angle that distinguishes clams from most other animal protein sources.

Clams are filter feeders — they require no feed inputs, no fresh water, no agricultural land, and no fertilizers or pesticides. They actively improve water quality by filtering phytoplankton, bacteria, and organic particles from seawater — a single clam can filter tens of liters of seawater a day.

Clam farming (aquaculture) is considered one of the most sustainable forms of animal food production available:

• Zero feed inputs — clams feed on naturally occurring algae (phytoplankton), requiring no fishmeal or agricultural feed
• Carbon — clam shells lock carbon into calcium carbonate, though whether shellfish farming is a net carbon sink is debated, because shell formation itself releases some CO2
• Water quality improvement — clam beds actively clean the water they inhabit
• Low land use — offshore and nearshore aquaculture requires no terrestrial land

For people who want to include animal protein in their diet while minimizing environmental impact, clams and other bivalves (oysters, mussels, scallops) represent one of the most ethical and sustainable options available — simultaneously providing extraordinary nutrition and environmental benefits.

Clams for Athletes and Active People

Iron for Aerobic Performance

Iron deficiency is the most common nutritional deficiency among endurance athletes — particularly female runners and cyclists. Even without frank anaemia, low iron stores (ferritin) can impair endurance capacity and increase fatigue during training.

Clams provide useful iron — 16% of the daily value per 100g in USDA’s data, more in some products — alongside the B12 and copper that red blood cell production also depends on, making them a worthwhile part of an iron-conscious diet for active people.

B12 for Red Blood Cell Production

B12 is required alongside iron and folate for the production of healthy red blood cells. Athletes with even marginal B12 deficiency may experience reduced red blood cell production that impairs oxygen-carrying capacity and aerobic performance. Clams are an extraordinary B12 source and a useful iron source — covering two of the most important nutritional drivers of red blood cell health in a single food.

Exceptional Protein Efficiency for Athletes Cutting Calories

During fat loss phases where every calorie counts, 25.6g of complete protein at 148 calories — about 0.17g of protein per calorie — makes clams an efficient protein source. A 150g serving of clams provides 38g of protein at 222 calories — slightly more calories than chicken breast for the same protein, but with vastly more B12, selenium, and copper.

Selenium for Antioxidant Recovery

Intense exercise dramatically increases free radical production and oxidative stress. Clams’ 116% DV selenium per 100g supports the glutathione peroxidase activity that neutralizes exercise-induced oxidative damage — helping maintain the antioxidant defense systems that support recovery between training sessions.

Taurine for Muscle Function

Taurine is concentrated in clams and has been studied — mostly as a supplement, at doses higher than food provides — for several roles relevant to athletic performance:

• Improving calcium handling in muscle fibers, which may support force production
• Reducing exercise-induced oxidative damage in muscle tissue
• Supporting cardiovascular efficiency during exercise
• Possibly reducing muscle cramping through its effects on ion channel regulation

Meta-analyses have found small improvements in endurance performance with taurine supplementation — dietary taurine from foods like clams contributes to the body’s taurine pool, though at lower doses than those studies used.

The Sodium Consideration

At 1,202mg of sodium per 100g, clams are a sodium-significant food — with a standard 85g serving providing approximately 1,022mg (44% of the 2,300mg daily limit).

Context for This Sodium Level

Natural vs. added sodium — unlike the sodium in beef jerky, which is added during processing, much of clams’ sodium is natural — clams live in saltwater and their tissues reflect the salinity of their environment. This natural sodium comes packaged alongside the extraordinary nutritional profile described above.

For active people with high sweat sodium losses — athletes training intensely in warm conditions can lose 1,000mg or more of sodium per hour through sweat. For these individuals, the sodium in a serving of clams partially replenishes sweat losses rather than contributing to excess intake.

For people managing blood pressure — those with hypertension or cardiovascular disease should account for clams’ sodium within their daily budget. Pairing clams with high-potassium foods (the 628mg potassium in clams itself helps, alongside vegetables and fruits) helps counteract sodium’s blood pressure effects.

Canned vs. fresh — canned clams can have even higher sodium than fresh-cooked clams due to brining during canning. Rinsing canned clams reduces sodium somewhat, and choosing no-salt-added varieties reduces it further.

Different Types of Clams

Several clam species are commonly eaten, each with slightly different flavor profiles and preparation applications:

Little neck clams — small, tender clams commonly eaten raw on the half shell or steamed. Delicate, sweet flavor. Most popular for raw applications.

Cherrystone clams — medium-sized. Eaten raw by some, but most often steamed, stuffed, or chopped for chowder.

Quahog clams (chowder clams) — the largest hard-shell variety. Tougher texture, more intensely flavored. Almost exclusively used chopped in chowder and cooked preparations.

Soft-shell clams (steamers) — the classic New England steamer clam. Softer, sweeter flavor. Traditionally steamed and served with drawn butter. The siphon (neck) is edible.

Manila clams — small, sweet, tender. Popular in Asian cooking and pasta dishes. Very quick cooking time.

Geoduck clams — the largest burrowing clam, native to the Pacific Northwest. Extremely sweet, crunchy meat. Considered a delicacy in Japanese and Chinese cuisine.

All varieties share the exceptional B12 and selenium profile described above — specific nutrient concentrations vary between species, and iron in particular varies widely.

Fresh vs. Canned Clams: Nutritional Comparison

Fresh Clams

Nutritional profile — as presented on this page.

Preparation — requires cleaning (scrubbing shells, soaking in salted water to purge sand), steaming or other cooking. More time-intensive but superior flavor and texture for most applications.

Availability — seasonal and regional. Best quality at coastal fish markets.

Safety — must be cooked thoroughly. Live clams must be alive before cooking (shells should close when tapped). Discard any that don’t open during cooking.

Canned Clams

Convenience — the most practical form for everyday cooking. Ready to use with no preparation.

Nutritional profile — comparable to fresh-cooked clams for most nutrients. B12, selenium, and protein are well retained through the canning process, though iron varies widely between products.

Sodium — significantly higher than fresh in most canned products due to brine. Rinsing reduces sodium somewhat; choosing no-salt-added varieties minimises it.

Clam juice — the liquid in canned clams contains water-soluble B vitamins and potassium (along with plenty of sodium). Use it in chowders, pasta sauces, and seafood dishes rather than discarding it.

Clams vs. Other Shellfish: Nutritional Comparison

Clams stand out dramatically in this comparison — for B12 (more than four times mussels, the next highest) and protein density, with selenium second only to mussels. Iron is a different story: on USDA’s current figures, oysters (51% DV) and mussels (37% DV) provide considerably more iron than clams (16% DV). Clams’ sodium is the main trade-off — the highest in this group. Shrimp B12 and selenium are from USDA’s older cooked-shrimp analysis; its other values are for plain cooked shrimp, as on our shrimp page.

Practical Ways to Include Clams in Your Diet

Clam linguine — the Italian classic. Sauté garlic in olive oil, add white wine and fresh or canned clams, toss with al dente linguine and fresh parsley. One of the most nutritionally complete pasta dishes possible — B12, selenium, protein, and healthy fats in one preparation. The lemon typically added brightens flavor while providing Vitamin C that helps iron absorption.

Clam chowder — creamy clam chowder or Manhattan (tomato-based) chowder are both practical ways to consume clams in comforting, filling form. Use canned clams for weeknight convenience. Add clam juice for intensified flavor and additional nutrients.

Steamed clams — the simplest preparation. Steam fresh clams in white wine, garlic, and butter for 5–7 minutes until shells open. Serve with crusty bread to soak up the broth — one of the most flavorful and nutritious meals achievable with minimal preparation.

Clams casino — stuffed clams baked with breadcrumbs, bacon, peppers, and herbs. A classic preparation that makes clams accessible to people who find plain clams too flavorful.

Canned clams in pasta, rice, or grain bowls — the most practical everyday application. A tin of clams added to any grain dish with olive oil, garlic, herbs, and lemon creates a nutritionally exceptional meal in minutes.

Clam dip — a classic American preparation of cream cheese, sour cream, and minced clams used as a dip with crackers or vegetables. A practical way to include clams in a social eating context.

Raw on the half shell — little neck clams served raw on ice with lemon and hot sauce. The most immediate and traditional way to appreciate fresh clams — though raw shellfish carry a risk of Vibrio and other infections, so they’re best avoided by anyone pregnant, immunocompromised, or with liver disease.

Potential Considerations

Sodium content — 1,202mg per 100g is significant. People with hypertension, cardiovascular disease, or strict sodium restrictions should account for this within their daily budget and choose fresh clams over canned where possible.

Shellfish allergy — shellfish allergy is one of the most common food allergies and can cause severe, potentially life-threatening reactions. Clam allergy specifically (as distinct from crustacean shellfish allergy) falls under the mollusc category. People with known shellfish allergies must avoid clams.

Food safety — clams are filter feeders that can concentrate pathogens, heavy metals, and marine biotoxins from contaminated water. Always source clams from reputable suppliers with verified water quality certification. Cook thoroughly — steamed clams are done when their shells open, and any that stay closed should be discarded. Never eat clams harvested from waters of unknown quality.

Red tide and paralytic shellfish poisoning — during harmful algal bloom (red tide) events, filter-feeding bivalves can accumulate paralytic shellfish toxins. Always check local advisories before harvesting wild clams. Commercial clams from regulated suppliers are routinely tested and safe.

Gout — clams contain purines that metabolize to uric acid. People with gout or hyperuricaemia should limit high-purine seafood including clams during flare-ups.

Pregnancy — cooked clams are generally safe during pregnancy and their B12 content is particularly valuable for pregnant women. Raw clams should be avoided during pregnancy due to risk of Vibrio and other foodborne pathogens.

Heavy metals — filter feeders can concentrate mercury and other heavy metals from their environment. Clams generally have lower mercury levels than large predatory fish because they are low on the food chain — but sourcing from clean, certified waters is important.

Nutrient data: USDA FoodData Central, SR Legacy — clams, mixed species, cooked, moist heat (FDC ID 171975). % Daily Values use the FDA’s current Daily Values.