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 times the daily requirement. Forty-one times. In 148 calories.

Clams are the most concentrated source of Vitamin B12 available from any commonly eaten food — including beef liver, which is itself legendary for its B12 content. They are also extraordinary for iron (77% DV), selenium (112% DV), phosphorus (41% DV), potassium (628mg), and they deliver 25.5g of complete protein at just 148 calories — one of the most impressive protein-to-calorie ratios of any food in any category.

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 almost every metric that matters.

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)

Standout: The 4,120% daily value of Vitamin B12 per 100g of cooked clams is not only the highest in your nutrition facts section — it is one of the highest B12 concentrations found in any commonly consumed food on earth. For context: the daily requirement for B12 is 2.4µg. A 100g serving of clams provides 98.9µg — over 41 days’ worth of B12 in a single serving. This is important not just as a striking statistic but as a practical nutritional fact: a single serving of clams per week provides more than sufficient B12 to maintain optimal status in virtually any adult.

Minerals in Clams (per 100g, cooked)

Multiple standouts: Clams are a genuinely extraordinary mineral source:

Selenium at 112% 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.

Iron at 77% DV — and crucially, this is haem iron — the highly bioavailable form found only in animal products, absorbed at 25–35% efficiency versus 2–20% for plant iron. 77% of daily iron in 148 calories with exceptional bioavailability makes clams one of the most important iron foods available for anyone at risk of deficiency.

Phosphorus at 41% 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 22% 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 — bioaccumulate B12 from the marine bacteria they filter and consume over their lifetime.

This concentration mechanism operates similarly to how large fish bioaccumulate mercury — but in this case the accumulated compound is nutritionally beneficial rather than harmful. 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 — oysters, mussels, scallops — use the same filter-feeding mechanism and similarly have exceptional B12 content, though typically not as extreme as clams.

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, impairing the intrinsic factor-dependent B12 absorption mechanism
• Vegetarians and vegans: B12 is found only in animal products
• People taking metformin (common diabetes medication): metformin impairs B12 absorption
• People with pernicious anaemia: autoimmune destruction of intrinsic factor cells
• 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 corrective food. For non-vegans who are B12 deficient or at risk, regular clam consumption — even once per week — provides vastly more than the daily requirement and can restore and maintain optimal B12 status. A single 85g serving provides 3,502% of the daily B12 requirement — more than two years’ worth of daily B12 if it were all stored (which it is not, but B12 stores in the liver can last 3–5 years when regularly replenished).

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 an independent cardiovascular risk factor that damages arterial endothelium. Adequate B12 from clams directly reduces cardiovascular risk through this pathway.

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: Haem Iron at 77% DV

At 13.9mg of iron per 100g — 77% of the daily value — clams are one of the most iron-dense foods available in the entire human diet. More importantly, this is haem iron — the form found only in animal products that is absorbed with dramatically greater efficiency than non-haem iron from plant sources.

Haem vs. Non-Haem Iron

This means the 13.9mg of haem iron in 100g of clams delivers approximately 3.5–4.9mg of absorbed iron — compared to the same amount of non-haem iron which would deliver only 0.3–2.8mg absorbed.

Why This Matters for Iron Deficiency

Iron deficiency is the world’s most common nutritional deficiency — affecting approximately 2 billion people globally. It is the leading cause of anaemia worldwide, with symptoms including:

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

For people with iron deficiency or iron deficiency anaemia — particularly premenopausal women, pregnant women, endurance athletes, and vegetarians/vegans who eat fish but not meat — clams represent one of the most efficient dietary iron sources available. A single serving of clams can provide more absorbed iron than a full day’s worth of plant-based iron sources.

Iron and Vitamin C

While clams’ haem iron doesn’t require Vitamin C for enhanced absorption (unlike non-haem iron), consuming clams in dishes that include Vitamin C-rich ingredients — lemon juice in clam linguine, tomatoes in clam chowder, fresh herbs — is a classic culinary pairing that simultaneously optimises the iron contribution of any plant ingredients in the dish.

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 tools for protecting neurological health. Regular consumption — even once weekly — provides sufficient B12 to maintain optimal status, prevent the progressive neurological damage of deficiency, and support the full range of B12-dependent neurological functions.

For older adults specifically — the population most vulnerable to B12 deficiency due to declining stomach acid and intrinsic factor production — clams are one of the most practical and affordable dietary interventions for protecting long-term cognitive and neurological health.

Exceptional Protein Efficiency

At 25.5g of complete protein per 100g for just 148 calories, clams provide one of the best protein-to-calorie ratios of any food — better than chicken breast (31g protein per 165 calories = 0.19g/cal), comparable to tuna (26g per 116 calories = 0.22g/cal), and extraordinary considering their additional micronutrient density.

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 represent one of the most calorie-efficient protein sources available from any whole food.

Outstanding Selenium for Antioxidant Defence

At 112% 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 reduction — as discussed, B12 from clams directly lowers cardiovascular risk through homocysteine metabolism.

Omega-3 fatty acids — while clams contain modest amounts of omega-3 (approximately 0.4g of polyunsaturated fat per 100g, a portion of which is EPA and DHA), their contribution to the dietary omega-3 balance is meaningful.

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

Very low saturated fat — at just 0.3g 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 with documented cardiovascular benefits including blood pressure reduction, improved cardiac contractility, and antiarrhythmic effects. Research has associated higher taurine intake with reduced cardiovascular disease risk across multiple large population studies.

Iron for Oxygen Transport and Energy

The 77% DV haem iron per 100g directly 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 iron deficiency or iron deficiency anaemia — a surprisingly common condition, particularly in female endurance athletes and plant-dominant eaters — regular clam consumption can meaningfully improve iron status, aerobic performance, and energy levels.

Thyroid Function

The combination of selenium (112% DV) and iodine — naturally present in all 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). Many people who are iodine-insufficient also have suboptimal selenium status — addressing both through seafood consumption supports optimal thyroid function and the metabolic rate that thyroid hormones regulate.

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 — consistently impairs 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 in clams acts as an inhibitory neurotransmitter in the brain, reducing neuronal excitability and having potential anxiolytic and sleep-supporting effects.

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 clam can filter up to 40 liters of seawater per day.

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

• Zero feed inputs — clams photosynthesise through their algae diet, requiring no fishmeal or agricultural feed
• Carbon sequestration — clam shells incorporate carbon dioxide from seawater into calcium carbonate shells, helping remove CO2 from the marine environment
• 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) consistently impair VO2 max, reduce time to exhaustion, and decrease perceived energy during training.

The 77% DV of haem iron per 100g in clams — with its exceptional bioavailability — makes regular clam consumption one of the most practical dietary strategies for maintaining optimal iron status in active populations. A single serving of clams can contribute more absorbed iron than several servings of plant-based iron sources combined.

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 address both B12 and iron simultaneously — covering the two 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, 25.5g of complete protein at 148 calories — a protein-to-calorie ratio of 0.17g per calorie — is one of the most efficient protein sources available. A 150g serving of clams provides 38g of protein at just 222 calories — substantially better than chicken breast at equivalent protein.

Selenium for Antioxidant Recovery

Intense exercise dramatically increases free radical production and oxidative stress. Clams’ 112% DV selenium per 100g supports the glutathione peroxidase activity that neutralizes exercise-induced oxidative damage — helping maintain the antioxidant defense systems that support faster recovery between training sessions.

Taurine for Muscle Function

Taurine is concentrated in clams and plays several roles directly relevant to athletic performance:

• Improves calcium sensitivity in muscle fibers — enhancing force production
• Reduces exercise-induced oxidative damage in muscle tissue
• Supports cardiovascular efficiency during exercise
• Reduces muscle cramping through its effects on ion channel regulation

Research has found taurine supplementation improves exercise capacity in trained athletes — and dietary taurine from foods like clams contributes to the taurine pool that supports these effects.

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 or canned foods which is primarily added during processing or preservation, a significant portion 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 1,000–2,000mg 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) counteracts 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 by approximately 30%. Choosing canned-in-water varieties rather than brine significantly reduces sodium content.

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. Too large for raw consumption by most people, ideal for steaming, stuffing, or chopping 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 clam species, native to the Pacific Northwest. Extremely sweet, crunchy meat. Considered a delicacy in Japanese and Chinese cuisine.

All varieties share the exceptional B12, iron, and selenium profile described above — specific nutrient concentrations vary modestly between species but the dramatic figures are consistent across clam types.

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, iron, selenium, and protein are well retained through the canning process.

Sodium — significantly higher than fresh in most canned products due to brine. Rinsing reduces sodium by approximately 30%. Choosing no-added-salt or “packed in water” varieties minimises this.

Clam juice — the liquid in canned clams is nutritionally valuable — containing water-soluble B vitamins, potassium, and other nutrients. 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 — particularly for B12 (far exceeding any other shellfish), iron (the highest by a significant margin), and protein density. Their sodium content is the main trade-off compared to alternatives like mussels, scallops, and shrimp.

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, iron, selenium, protein, and healthy fats in one preparation. The lemon typically added brightens flavor while providing Vitamin C that optimizes iron absorption from the clams.

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 — providing the full nutritional profile in its least processed form.

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 — clam flesh should reach an internal temperature of 74°C. Never consume clams from unpolluted water status unknown.

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 and iron 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.