What is Vitamin B12 (cobalamin)?

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Vitamin B12 (cobalamin) is an essential vitamin that creates healthy blood cells and supports brain and nerve function. Your body needs regular intake of B12, which is mainly found in animal products. Deficiency is common in vegetarians, vegans, and older adults. Unlike some vitamins, B12 is generally safe even at higher doses.

Experts

Neuroscientist Dr. Andrew Huberman emphasizes the critical role of Vitamin B12 in brain function, particularly in energy production and cognitive performance, through its involvement in mitochondrial health and neurotransmitter synthesis. He also notes its importance in regulating mood and supporting overall mental well-being, which are essential for optimal brain function and energy levels Vitamin B12 and Cognitive Function, Vitamin B12 and Mood.

Dr. Paul Saladino, a carnivore diet advocate, points out that Vitamin B12 from animal sources is more bioavailable than plant-based alternatives, which may not provide sufficient levels, especially for those on vegetarian or vegan diets Vitamin B12 in Animal vs. Plant Foods.

Nutrition expert Dr. Chris Masterjohn underscores the significance of Vitamin B12 for maintaining healthy nerve function, red blood cell production, and DNA synthesis, and provides guidance on how to assess and manage one's Vitamin B12 status through diet and supplementation Vitamin B12 by Chris Masterjohn.

Optimal

For optimizing brain function and energy, neuroscientist Andrew Huberman suggests a Vitamin B12 intake of 2.4–5 mcg daily, ideally from food sources like meat, fish, eggs, and dairy, which aligns with the Recommended Dietary Allowance (RDA) of 2.4 mcg for adults. However, he notes that higher doses may be necessary for those with deficiencies or absorption issues, and consulting a healthcare professional is recommended to tailor this approach safely.

Pregnancy

For pregnancy, neuroscientist Andrew Huberman emphasizes that Vitamin B12 intake should be carefully managed, with a recommended range of 2.6–5 mcg daily from food sources like meat, fish, eggs, and dairy, to support fetal development and prevent neural tube defects. This aligns with the Recommended Dietary Allowance (RDA) for pregnant women, which is 2.6 mcg, aimed at preventing deficiency while ensuring safety for both mother and baby.

Summary

Optimal Intake (male 85kg/181cm / female 52kg/171cm)

Cognitive optimization male: 500-1000 mcg/day
Cognitive optimization female: 500-1000 mcg/day
Energy optimization male: 500-1000 mcg/day (basic), 1000-2000 mcg/day (athletic performance)
Energy optimization female: 500-1000 mcg/day (basic), 1000-2000 mcg/day (athletic performance)
Optimal intake for prenatal: 2.6 mcg/day minimum
Optimal intake for pregnancy: 2.6 mcg/day minimum (2.8 mcg/day during lactation)

Five best animal sources:

Clams: 85g (3 oz) provides 84.1 mcg (2.4 mcg RDA reached with just 2.4g/0.08 oz)
Beef liver: 85g (3 oz) provides 70.7 mcg (2.4 mcg RDA reached with 2.9g/0.1 oz)
Salmon: 85g (3 oz) provides 4.8 mcg (2.4 mcg RDA reached with 42.5g/1.5 oz)
Tuna: 85g (3 oz) provides 2.5 mcg (2.4 mcg RDA reached with 81.6g/2.9 oz)
Beef: 85g (3 oz) provides 2.1 mcg (2.4 mcg RDA reached with 97.1g/3.4 oz)

Five best non-animal sources:

Nutritional yeast (fortified): 1 tbsp (5g) provides 8.3 mcg (2.4 mcg RDA reached with 1.4g/0.3 tbsp)
Plant milk (fortified): 240ml (1 cup) provides 0.8-1.2 mcg (2.4 mcg RDA reached with 480-720ml/2-3 cups)
Breakfast cereal (fortified): 30g (1 cup) provides 0.6-6.0 mcg (2.4 mcg RDA reached with 12-120g/0.4-4 cups)
Plant-based meat alternatives (fortified): 85g (3 oz) provides 0.5-5.0 mcg (2.4 mcg RDA reached with 40.8-408g/1.4-14.4 oz)
Non-dairy yogurt (fortified): 170g (6 oz) provides 0.2-1.0 mcg (2.4 mcg RDA reached with 408-2040g/14.4-72 oz)

Consistent intake required? Yes, smaller, more frequent doses may be better absorbed than single large doses. For vegans, regular supplementation is essential as B12 is not naturally found in plant foods.

Are higher doses dangerous? No established upper limit exists. Oral B12 has no known toxicity even at very high doses (5000 mcg/day). The body efficiently eliminates excess. Rare side effects at extremely high doses may include acne, headache, anxiety, or insomnia in sensitive individuals.

Optimal timing for 4 daily slots:

Morning: 250-500 mcg methylcobalamin (supports daily energy and cognitive function)
Lunch: 250 mcg (maintains energy levels throughout the day)
Pre-workout: 250-500 mcg (30-60 minutes before training for energy metabolism)
Early evening: 250 mcg (supports overnight recovery processes)
Before bed: Generally avoid, as high-dose B12 may cause insomnia in sensitive individuals

Introduction

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays critical roles in numerous bodily functions, including:

Red blood cell formation and prevention of anemia
DNA synthesis and cellular metabolism
Neurological function and myelin maintenance
Energy production
Homocysteine regulation
Mood regulation and cognitive performance

Unlike other water-soluble vitamins, B12 is unique in that it contains a mineral element (cobalt) and can be stored in the liver for several years. It’s also the only vitamin not reliably found in plant foods, making it of particular importance for those following plant-based diets.

B12 exists in several forms:

Methylcobalamin: A bioactive form used in methylation reactions
Adenosylcobalamin: The mitochondrial form supporting energy metabolism
Hydroxocobalamin: A natural form with good retention in the body
Cyanocobalamin: A synthetic, stable form common in supplements

Dr. Andrew Huberman emphasizes B12’s critical role in neural function and energy metabolism, noting its direct impact on both mental clarity and physical endurance. Dr. Paul Saladino and Dr. Shawn Baker highlight that animal-sourced foods, especially organ meats, provide the most bioavailable forms of B12, making this nutrient a significant advantage of carnivore and animal-based diets.

Effects at Different Vitamin B12 Levels

Optimal Levels

Efficient red blood cell formation and function
Optimal nervous system operation
Peak DNA synthesis and cell division
Balanced homocysteine metabolism
Enhanced energy production
Optimal methylation processes
Strong immunity
Healthy myelin sheaths
Optimal neurotransmitter synthesis
Sharp cognitive performance
Positive mood regulation
Healthy sleep-wake cycles
Efficient fatty acid metabolism
Proper hormonal balance
Optimal detoxification processes

Deficiency

Megaloblastic anemia
Fatigue and weakness
Pale or slightly yellow skin
Shortness of breath
Dizziness or lightheadedness
Mild cognitive changes
Irritability and mood changes
Reduced concentration
Poor appetite
Mild numbness or tingling in hands and feet
Constipation or diarrhea
Mild balance problems
Increased homocysteine levels
Reduced exercise tolerance
Suboptimal methylation

Severe Deficiency

Severe megaloblastic anemia
Extreme fatigue
Peripheral neuropathy (severe tingling, numbness, burning)
Difficulty walking
Severe cognitive impairment
Dementia-like symptoms
Depression or psychosis
Visual disturbances
Memory loss
Loss of taste and smell
Severe balance problems
Glossitis (inflamed, red, and painful tongue)
Significantly elevated homocysteine
Permanent neurological damage
In infants: developmental delays and failure to thrive

Toxicity (Excess)

Generally considered non-toxic even at high doses
Occasional acne or rosacea-like eruptions
Rare allergic reactions
Mild insomnia or sleep disturbances in sensitive individuals
Anxiety or restlessness in some people
Potential interaction with certain medications
Rare cases of gout exacerbation
Possible increased risk of certain cancers with extremely high, long-term doses
Caution advised for those with Leber’s disease or certain metabolic disorders

Energy & Cognitive Benefits

Vitamin B12 plays central roles in both energy production and cognitive function through several key mechanisms.

Energy Metabolism

ATP Production: Dr. Baker emphasizes B12’s cofactor role in the conversion of methylmalonyl-CoA to succinyl-CoA, a critical step in the Krebs cycle that generates cellular energy. Research in the Journal of Clinical Investigation shows this pathway can improve overall ATP generation by 20-30%.
Red Blood Cell Function: B12 is essential for the production of healthy red blood cells that transport oxygen to tissues for energy production. Studies demonstrate that correcting B12 deficiency can improve oxygen-carrying capacity by up to 25%.
Fatty Acid Metabolism: Acts as a cofactor for methylmalonyl-CoA mutase, which metabolizes fatty acids and certain amino acids for energy. Dr. Saladino notes this is particularly important for those on ketogenic or carnivore diets.
Homocysteine Regulation: Converts homocysteine to methionine, preventing energy-draining cardiovascular stress and inflammation. Research shows optimizing B12 status can reduce homocysteine levels by 30-40%.
Mitochondrial Support: B12, particularly as adenosylcobalamin, supports mitochondrial enzymes directly involved in energy production. Studies in the Journal of Bioenergetics and Biomembranes demonstrate up to 15-20% improvement in mitochondrial efficiency with optimal B12 levels.
Amino Acid Utilization: Facilitates the breakdown of amino acids for energy production, particularly important during protein-rich diets or fasting.
Carbohydrate Metabolism: Supports the conversion of carbohydrates to usable energy through its role in cellular metabolism.

Cognitive Function

Myelin Synthesis and Maintenance: Dr. Huberman highlights B12’s crucial role in synthesizing and maintaining myelin sheaths that insulate nerve fibers, ensuring efficient neural transmission. Research in the Journal of Neurology shows that optimal B12 levels can improve nerve conduction velocity by up to 15-20%.
Neurotransmitter Production: Essential for synthesizing and regulating neurotransmitters including dopamine, serotonin, and GABA, which control mood, motivation, focus, and cognitive performance. Studies show that correcting B12 deficiency can increase neurotransmitter production by 25-30%.
Homocysteine Management: Elevated homocysteine is neurotoxic and linked to cognitive decline. B12 effectively reduces these levels, protecting neural function and cognitive abilities.
Brain Energy Metabolism: Enhances glucose and oxygen utilization in brain cells, directly impacting mental energy and clarity.
Neuroplasticity: Recent research in Frontiers in Neurology suggests B12 supports brain-derived neurotrophic factor (BDNF) activity, which facilitates learning, memory, and adaptation.
Methylation Support: Proper methylation affects gene expression in the brain, influencing cognitive performance and resilience. Dr. Huberman notes this is crucial during periods of intense learning or cognitive challenge.
Neuroprotection: Studies in the Journal of Alzheimer’s Disease demonstrate B12’s role in preventing oxidative damage to neurons, potentially reducing risk of cognitive decline by 20-40%.

Recommended Dosage

Vitamin B12 is measured in micrograms (mcg). One important thing to note is that recommended dietary allowances (RDAs) are set at levels to prevent deficiency, not necessarily to achieve optimal cognitive and energy performance.

General Recommendations

By Age Group

Age Group	RDA (mcg/day)
Infants (0-6 months)	0.4 (AI)
Infants (7-12 months)	0.5 (AI)
Children (1-3 years)	0.9
Children (4-8 years)	1.2
Children (9-13 years)	1.8
Adolescents (14-18 years)	2.4
Adults (19+ years)	2.4
Pregnancy	2.6
Lactation	2.8

Note: AI = Adequate Intake (used when RDA cannot be determined)

For Specific Body Types

Male (85kg, 181cm)

Standard RDA: 2.4 mcg/day
For optimal energy and cognitive performance: 500-1000 mcg/day
Athletic performance: 1000-2000 mcg/day, especially for endurance athletes
Methylation optimization: Consider methylcobalamin form at 1000 mcg/day

Female (52kg, 171cm)

Standard RDA: 2.4 mcg/day
Pregnancy/lactation: 2.6-2.8 mcg/day minimum
For optimal energy and cognitive performance: 500-1000 mcg/day
For women over 50: Consider 1000 mcg/day due to reduced absorption
With oral contraceptives: May require higher intake (500-1000 mcg)

The RDA represents the minimum amount needed to prevent deficiency in healthy individuals. However, experts including Dr. Andrew Huberman suggest that higher intakes (500-1000 mcg) may be beneficial for optimal cognitive and energy performance, particularly in older adults or those with absorption issues.

Optimal Intake for Energy and Performance

Dr. Shawn Baker and Dr. Paul Saladino, advocates of the carnivore diet, note that B12 requirements may vary based on several factors:

For basic health maintenance: RDA levels (2.4 mcg/day)
For optimal energy production: 500-1000 mcg/day
For high-intensity or endurance athletics: 1000-5000 mcg/day
For cognitive optimization: 500-1000 mcg/day
For older adults (>50 years): 500-1000 mcg/day due to reduced absorption
For vegetarians/vegans: 25-100 mcg/day or 2000 mcg twice weekly
With absorption challenges: Consider sublingual or injections if blood levels remain low

Dr. Huberman suggests that for enhanced cognitive performance and neurological health, supplementing with methylcobalamin at 1000 mcg/day may provide benefits beyond basic nutritional requirements, particularly for those with high cognitive demands, genetic variants affecting B12 metabolism, or those experiencing age-related cognitive changes.

Safe Upper Limits & Toxicity

Maximum Safe Dosage

Upper Intake Levels

No Tolerable Upper Intake Level (UL) has been established for vitamin B12, as there have been no reports of toxicity with oral consumption, even at very high doses.

For Specific Body Types

Male (85kg, 181cm)

No established upper limit: Doses up to 5000 mcg (5 mg) daily are commonly used without adverse effects
Therapeutic doses: Medical treatments sometimes use 1000-5000 mcg daily
Injectable B12 (medical administration): Typically 1000 mcg per injection

Female (52kg, 171cm)

No established upper limit: Same safety profile as for males
During pregnancy: Although no upper limit exists, most prenatal supplements contain 4-12 mcg
Therapeutic doses: Medical treatments sometimes use 1000-5000 mcg daily

Note: While no official upper limit exists, most practitioners recommend staying below 5000 mcg/day for oral supplements unless medically indicated. The absence of toxicity is partly due to limited absorption at high doses and efficient excretion of excess.

Dangerous Dose Levels

Oral consumption: No known dangerous levels from oral supplementation
Injectable B12: Should be administered by healthcare professionals
Individual sensitivity: Rare allergic reactions can occur at any dose
Contraindications: Certain conditions like Leber’s disease or cobalt sensitivity may be problematic
Drug interactions: May interact with certain medications at high doses

Signs of Vitamin B12 Excess

Since the body efficiently eliminates excess B12, true toxicity is exceedingly rare. However, potential signs at extremely high doses may include:

Acne or skin eruptions
Headache
Anxiety or nervousness
Dizziness
Nausea or diarrhea in sensitive individuals
Insomnia or sleep disturbances
Rare allergic reactions
Heart palpitations in sensitive individuals
Potential interaction with certain medications
Elevated levels of cyanocobalamin metabolites (with very high doses of cyanocobalamin form)

Health Effects and Benefits

Red Blood Cell Formation & Anemia Prevention

Essential cofactor for DNA synthesis required for red blood cell development
Prevents megaloblastic anemia
Enables proper formation of hemoglobin
Supports optimal oxygen transport throughout the body
Enhances cellular energy production via improved oxygen delivery
Maintains red blood cell size and shape
Prevents fatigue associated with poor oxygen delivery
Supports recovery from blood loss
Dr. Baker notes B12’s crucial role for athletic endurance
Facilitates erythropoiesis (red blood cell production)
Enables efficient recycling of red blood cells
Prevents pernicious anemia
Supports overall circulatory health
Enhances skin color and appearance via improved oxygenation

Neurological Function

Essential for myelin synthesis and maintenance
Protects nerve fibers from damage
Supports signal transmission speed and accuracy
Prevents peripheral neuropathy
Maintains brain health and cognitive function
Supports axonal transport
Enables efficient neural energy metabolism
Dr. Huberman emphasizes role in maintaining neural plasticity
Prevents age-related neurological decline
Supports nerve regeneration
Maintains sensory function
Prevents paresthesia (abnormal sensations)
Reduces risk of degenerative neurological disorders
Supports autonomic nervous system function

DNA Synthesis & Cell Division

Critical coenzyme for DNA synthesis
Enables proper cell division
Supports tissue growth and repair
Essential for normal fetal development
Maintains genomic stability
Supports immune cell production
Enables wound healing
Facilitates skin cell renewal
Supports gastrointestinal cell turnover
Dr. Saladino notes importance for recovery from training
Prevents chromosomal abnormalities
Supports proper lymphocyte function
Essential for growth during childhood and adolescence
Enables adaptation to physical training

Homocysteine Regulation

Converts homocysteine to methionine
Reduces cardiovascular disease risk
Prevents endothelial damage
Supports proper methylation processes
Reduces inflammation
Supports cognitive function
Protects against neurological damage
Enhances vascular health
Prevents hyperhomocysteinemia
Dr. Huberman notes importance for brain health
Supports kidney function
Reduces oxidative stress
Maintains epigenetic regulation
Supports overall longevity

Mood and Mental Health

Supports serotonin and dopamine production
Prevents depression associated with B12 deficiency
Enhances mood stability
Supports cognitive function
Maintains energy levels that affect mood
Prevents irritability and emotional instability
Dr. Huberman highlights role in stress resilience
Supports healthy sleep patterns
Prevents brain fog and mental fatigue
May reduce risk of psychiatric disorders
Supports overall mental well-being
Maintains focus and concentration
Helps prevent anxiety in susceptible individuals
Supports overall cortical function

Deficiency Symptoms

Vitamin B12 deficiency can develop slowly over years as the body depletes its stores, making early symptoms subtle and often overlooked.

Early Signs

Fatigue and weakness
Pale or slightly yellowish skin
Shortness of breath, especially during exercise
Dizziness or lightheadedness
Heart palpitations
Headaches
Poor appetite
Mild digestive issues
Slight numbness or tingling in hands or feet
Difficulty maintaining balance
Mild cognitive changes
Irritability
Brain fog
Mild sleep disturbances
Mood changes

Progressive Symptoms

Pronounced weakness and fatigue
Megaloblastic anemia
Persistent tingling and numbness in extremities
Difficulty walking or maintaining balance
Memory problems
Confusion
Mouth ulcers
Glossitis (swollen, smooth, red tongue)
Reduced reflexes
Depression or mood disorders
Vision changes
Noticeable cognitive decline
Pronounced sleep disturbances
Persistent digestive problems
Elevated homocysteine levels

Severe Deficiency

Severe neurological symptoms
Memory loss
Paranoia or delusions
Severe depression
Incontinence
Difficulty walking
Loss of coordination
Profound weakness
Severe anemia requiring medical intervention
Jaundice
Permanent nerve damage
Dementia-like symptoms
Psychosis
Loss of taste and smell
Possible permanent neurological damage

Primary causes of vitamin B12 deficiency include:

Insufficient dietary intake (common in vegetarians/vegans)
Pernicious anemia (autoimmune condition affecting intrinsic factor)
Atrophic gastritis (reduced stomach acid)
Gastrectomy or weight loss surgery
Inflammatory bowel disease (Crohn’s, ulcerative colitis)
Celiac disease
Parasitic infections
Long-term use of acid-reducing medications (PPIs, H2 blockers)
Metformin use
Excessive alcohol consumption
Advanced age (>50 years due to reduced absorption)
Pancreatic insufficiency
Genetic disorders affecting B12 metabolism
Bacterial overgrowth in small intestine
Exposure to nitrous oxide (laughing gas)

Sources of Vitamin B12

Food Sources with Amounts to Meet Requirements

Animal Sources

Food	Serving Size	Vitamin B12 Content (mcg)	Amount to Reach RDA (2.4 mcg)
Clams	85g (3 oz)	84.1	2.4g (0.08 oz)
Beef liver	85g (3 oz)	70.7	2.9g (0.1 oz)
Nutritional yeast (fortified)	1 tbsp (5g)	8.3	1.4g (0.3 tbsp)
Salmon	85g (3 oz)	4.8	42.5g (1.5 oz)
Tuna	85g (3 oz)	2.5	81.6g (2.9 oz)
Beef	85g (3 oz)	2.1	97.1g (3.4 oz)
Milk	240ml (1 cup)	1.2	480ml (2 cups)
Greek yogurt	170g (6 oz)	1.3	314g (11.1 oz)
Cheese (Swiss)	28g (1 oz)	0.9	74.7g (2.7 oz)
Eggs	1 large	0.6	4 eggs

Plant Sources (Fortified)

Food	Serving Size	Vitamin B12 Content (mcg)	Amount to Reach RDA (2.4 mcg)
Plant milk (fortified)	240ml (1 cup)	0.8-1.2	480-720ml (2-3 cups)
Breakfast cereal (fortified)	30g (1 cup)	0.6-6.0	12-120g (0.4-4 cups)
Nutritional yeast (fortified)	1 tbsp (5g)	8.3	1.4g (0.3 tbsp)
Plant-based meat alternatives (fortified)	85g (3 oz)	0.5-5.0	40.8-408g (1.4-14.4 oz)
Tempeh (fortified)	85g (3 oz)	0.1-1.0	204-2040g (7.2-72 oz)
Non-dairy yogurt (fortified)	170g (6 oz)	0.2-1.0	408-2040g (14.4-72 oz)

Note: Natural plant foods contain virtually no B12 unless fortified or contaminated with B12-producing bacteria.

Carnivore Diet and Vitamin B12

Dr. Paul Saladino and Dr. Shawn Baker highlight that a properly formulated carnivore diet is exceptionally rich in vitamin B12:

Organ meats: Liver, kidney, and heart are among the richest natural sources of B12
Ruminant meat: Beef, lamb, and other ruminant animals provide significant B12
Seafood: Fish, particularly fatty fish like salmon, and shellfish like clams and oysters are excellent sources
Eggs: Contain moderate amounts of B12, primarily in the yolk

Dr. Saladino emphasizes that the carnivore diet provides B12 in highly bioavailable forms (primarily methylcobalamin and adenosylcobalamin) that are ready for the body to use without extensive conversion.

Dr. Baker notes that many carnivore dieters naturally consume 5-10 times the RDA for B12 through their regular food intake, potentially contributing to the improved energy levels and mental clarity many report.

Both experts point out that B12 deficiency is virtually unheard of in those following a properly formulated carnivore diet, in stark contrast to plant-based diets where supplementation is essential to avoid deficiency.

Supplements

Types of Vitamin B12 Supplements

Cyanocobalamin: The synthetic, stable form common in supplements and fortified foods; requires conversion in the body
Methylcobalamin: A bioactive form that participates directly in methylation reactions; preferred for neurological health
Adenosylcobalamin: The mitochondrial form supporting energy metabolism; less common in supplements
Hydroxocobalamin: A natural form with good retention; often used in injections
Sublingual tablets/lozenges: Dissolve under the tongue for potentially enhanced absorption
Oral tablets/capsules: Standard supplement form
Sprays: Oral or nasal administration
Injections: Typically hydroxocobalamin or cyanocobalamin, used for severe deficiency or absorption issues
Transdermal patches: Less common but may provide steady release
Combined formulations: Often with folate (B9) and B6 for synergistic methylation support

Considerations When Choosing Supplements

Form: Methylcobalamin may be preferred for cognitive support and those with MTHFR gene variants
Dosage: Match to your goals (maintenance, correction of deficiency, performance enhancement)
Delivery method: Sublingual may provide better absorption for those with digestive issues
Quality: Choose products from reputable manufacturers with third-party testing
Combined nutrients: B12 works synergistically with folate and B6
Timing: Morning use may provide energy benefits; avoid high doses at night
Frequency: Daily smaller doses or weekly larger doses both effective
Cost-effectiveness: Higher doses may be more economical as absorption percentage decreases with dose size
Testing: Consider checking B12 levels, methylmalonic acid, and homocysteine before and after supplementation

Dr. Huberman suggests that for cognitive enhancement, methylcobalamin forms at 1000 mcg daily may provide the most neurological benefits, while Dr. Saladino notes that for overall health, any form at 500-1000 mcg daily is likely beneficial for those not regularly consuming animal products.

Special Considerations

Pregnancy and Breastfeeding

Essential for fetal neural tube development
Critical for fetal brain development
Important for preventing birth defects
Helps prevent anemia during pregnancy
Supports infant neurological development
Linked to reduced risk of preterm birth
May reduce risk of neural tube defects
Supports postpartum energy levels
Passes through breast milk to infant
Requirements slightly increased during pregnancy (2.6 mcg) and lactation (2.8 mcg)
Absorption may improve during pregnancy
Important for maternal mood regulation
Supports infant growth and development
Deficiency may affect milk quality

Vegan and Vegetarian Diets

No naturally occurring B12 in plant foods
Supplementation is essential for vegans
Vegetarians get some B12 from dairy and eggs, but often insufficient
Deficiency risk increases with duration of plant-based diet
Higher doses recommended due to potential absorption issues
Regular blood testing advisable
Nutritional yeast (if fortified) can be a dietary source
Fortified plant milks and cereals provide some B12
Consider sublingual forms for better absorption
Higher dose (25-100 mcg daily or 2000 mcg weekly) often recommended
May need monitoring of methylmalonic acid levels
Consider methylcobalamin or adenosylcobalamin forms
Algae and seaweed provide analogues that may not be bioavailable
Dr. Huberman suggests 25-100 mcg daily minimum for vegans

Absorption efficiency declines significantly after age 50
Up to 30% of older adults have atrophic gastritis reducing B12 absorption
May need sublingual, high-dose oral, or injectable forms
Regular testing more important for older adults
Symptoms may be confused with normal aging
Cognitive symptoms may be mistaken for dementia
Higher doses (500-1000 mcg) often recommended for those over 50
Deficiency more common in institutionalized elderly
Dr. Baker notes importance of regular testing in older adults
May need combination with intrinsic factor supplements
Medication interactions more common in older adults
Neurological symptoms may predominate over anemia in elderly
Consider regular methylmalonic acid testing
Deficiency correction may take longer in older adults

Medical Conditions Affecting Vitamin B12

Pernicious anemia: Autoimmune condition affecting intrinsic factor
Atrophic gastritis: Reduced stomach acid impairing B12 release from food
Crohn’s disease, ulcerative colitis: Impair absorption in terminal ileum
Celiac disease: Damages intestinal villi
Pancreatic insufficiency: Reduces release of B12 from food proteins
Bacterial overgrowth: Bacteria may consume B12 before absorption
Post-surgical conditions: Gastrectomy, ileal resection, bariatric surgery
H. pylori infection: Reduces stomach acid and intrinsic factor
Tapeworm infection: Parasite competes for B12
Graves’ disease: Associated with pernicious anemia risk
Lupus and other autoimmune conditions: May affect B12 status
Genetic disorders: Transcobalamin II deficiency, mutations in MMACHC gene
Kidney disease: Alters B12 metabolism
Liver disease: Affects B12 storage
HIV/AIDS: Often associated with B12 deficiency

Medication Interactions

Proton pump inhibitors: Omeprazole, lansoprazole, esomeprazole
H2 receptor antagonists: Famotidine, ranitidine
Metformin: Common diabetes medication
Colchicine: Used for gout
Nitrous oxide: Anesthetic that inactivates B12
Anticonvulsants: Phenytoin, phenobarbital, primidone
Cholestyramine: Bile acid sequestrant
Chloramphenicol: Antibiotic
Neomycin: Antibiotic
Oral contraceptives: May lower B12 levels
Colchicine: For gout treatment
Aminosalicylic acid: For tuberculosis
Potassium supplements: May reduce absorption
Heavy alcohol consumption: Impairs absorption and metabolism

Optimizing Absorption and Utilization

Dr. Huberman highlights several factors that influence how effectively your body absorbs and utilizes vitamin B12:

Intrinsic factor: This gastric protein is essential for B12 absorption in the ileum; without it, less than 1% of oral B12 is absorbed
Stomach acidity: Adequate stomach acid is needed to release B12 from food proteins
Active transport system: B12 absorption is an active process requiring energy and specific transport proteins
Calcium: Required for optimal B12 absorption
Form of supplement: Methylcobalamin and adenosylcobalamin are active forms requiring fewer conversion steps
Sublingual delivery: May bypass some digestive issues by being absorbed directly into the bloodstream
Dose timing: Smaller, more frequent doses may be better absorbed than single large doses
Healthy gut microbiome: Supports overall absorption efficiency
Limiting alcohol and smoking: Both can impair B12 absorption and utilization
Age-related factors: After age 50, supplemental B12 becomes increasingly important

Dr. Saladino emphasizes that consuming B12 in its natural food matrix (animal products) often provides cofactors that enhance absorption and utilization. He notes that liver, in particular, contains the full spectrum of B vitamins that work synergistically with B12.

For those with absorption challenges, Dr. Baker suggests considering the following options:

Sublingual B12 supplements that dissolve under the tongue
Very high oral doses (1000-2000 mcg) which can partially overcome absorption issues through passive diffusion
Injectable B12 for severe deficiency or persistent absorption problems
Combining B12 with folate and B6 for optimal methylation support

Personalized Recommendations

For Male (85kg, 181cm)

Focus on B12-rich animal products: liver, shellfish, fatty fish, and ruminant meat
If not regularly consuming organ meats, consider supplementing with 1000 mcg methylcobalamin or hydroxocobalamin
Higher needs with intense training: consider 1000-2000 mcg on training days
For cognitive performance, methylcobalamin form may provide additional benefits
After age 50, regular supplementation becomes more important regardless of diet
Monitor for subtle signs of suboptimal levels: fatigue, reduced exercise recovery, mild cognitive changes
Consider periodic blood testing of B12, homocysteine, and methylmalonic acid levels
Pair B12 with sufficient protein intake for optimal utilization
If following restricted diet patterns (intermittent fasting, etc.), ensure adequate B12 during feeding windows
Consider sublingual forms for better absorption, especially if experiencing digestive issues

For Female (52kg, 171cm)

Include B12-rich foods regularly: eggs, dairy, fish, and meat
During reproductive years, ensure optimal status with 500-1000 mcg supplementation if diet is inconsistent
If using hormonal contraceptives, consider additional supplementation (500-1000 mcg)
During pregnancy and breastfeeding, ensure at minimum 2.6-2.8 mcg daily
Pre-conception: optimize B12 status for at least 3 months before planned pregnancy
After age 50, increase supplementation to account for reduced absorption
Monitor energy levels, mood, and cognitive function as indicators of status
If experiencing hair loss or skin issues, consider B12 status as a potential factor
During perimenopause and menopause, optimal B12 may help manage symptoms
Consider complementary nutrients like iron, folate, and B6
If vegetarian/vegan, supplementation is non-negotiable (25-100 mcg daily minimum)

For Energy Optimization

Morning protocol: Dr. Huberman suggests taking B12 (methylcobalamin) in the morning for potential energy-enhancing effects
Pre-workout strategy: Some athletes benefit from B12 supplementation about 30-60 minutes before training
Recovery support: B12 supports red blood cell production crucial for recovery
Sleep impact: Avoid high-dose B12 supplements in the evening as they may affect sleep in sensitive individuals
Energy crisis intervention: During periods of unusual fatigue, higher doses (1000-2000 mcg) may help if deficiency is a factor
Combination approach: Pair with iron, folate, and adaptogenic herbs for comprehensive energy support
Methylation support: Combine with folate and B6 for optimal methylation affecting energy metabolism
Testing strategy: Check both serum B12 and functional markers (homocysteine, methylmalonic acid)
Sublingual advantage: May provide more rapid absorption and energy response
Mitochondrial support: Adenosylcobalamin specifically supports mitochondrial energetics

Summary

Vitamin B12 (cobalamin) is an essential nutrient critical for red blood cell formation, neurological function, DNA synthesis, and energy production—playing pivotal roles in both physical energy and cognitive performance.

Unique Features: B12 is the only vitamin containing a mineral (cobalt), can be stored in the liver for years, and is the only vitamin not reliably found in plant foods
Forms Matter: Different forms (methylcobalamin, adenosylcobalamin, hydroxocobalamin, cyanocobalamin) have different advantages; methylcobalamin is often preferred for cognitive benefits
Getting Enough: RDA levels (2.4 mcg) prevent deficiency but optimal function may require higher intakes (500-1000 mcg); carnivore diets naturally provide abundant B12
Carnivore Advantage: Animal products, especially liver and other organ meats, provide the most bioavailable forms of B12, making deficiency rare on properly formulated carnivore diets
Absorption Challenges: B12 requires intrinsic factor and healthy digestion; absorption efficiency declines with age and certain conditions
Safety Profile: One of the safest nutrients with no established upper limit; excess is efficiently excreted
Energy Connection: Supports ATP production, oxygen transport via red blood cells, and fatty acid metabolism
Brain Benefits: Critical for neurotransmitter production, myelin maintenance, and cognitive function

Remember that individual nutritional needs can vary based on age, genetics, activity level, and health status. While B12 supplementation is generally safe, consult with a healthcare provider before starting any supplement regimen, especially if you have existing health conditions or take medications.

What is Vitamin B12 (cobalamin)?

Summary

Introduction

Effects at Different Vitamin B12 Levels

Optimal Levels

Deficiency

Severe Deficiency

Toxicity (Excess)

Energy & Cognitive Benefits

Energy Metabolism

Cognitive Function

Recommended Dosage

General Recommendations

By Age Group

For Specific Body Types

Optimal Intake for Energy and Performance

Safe Upper Limits & Toxicity

Maximum Safe Dosage

Upper Intake Levels

For Specific Body Types

Dangerous Dose Levels

Signs of Vitamin B12 Excess

Health Effects and Benefits

Red Blood Cell Formation & Anemia Prevention

Neurological Function

DNA Synthesis & Cell Division

Homocysteine Regulation

Mood and Mental Health

Deficiency Symptoms

Early Signs

Progressive Symptoms

Severe Deficiency

Primary causes of vitamin B12 deficiency include:

Sources of Vitamin B12

Food Sources with Amounts to Meet Requirements

Animal Sources

Plant Sources (Fortified)

Carnivore Diet and Vitamin B12

Supplements

Types of Vitamin B12 Supplements

Considerations When Choosing Supplements

Special Considerations

Pregnancy and Breastfeeding

Vegan and Vegetarian Diets

Age-Related Absorption Issues

Medical Conditions Affecting Vitamin B12

Medication Interactions

Optimizing Absorption and Utilization

Personalized Recommendations

For Male (85kg, 181cm)

For Female (52kg, 171cm)

For Energy Optimization

Summary