Component

Serum cobalamin concentration

Independent substance, clinical endpoint or measured readout; study context is retained with each finding.

6 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

Read recorded mechanisms Open recursive mind map

How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

Tracing routes…

What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What it acts on

  1. Serum B12 remained normal despite the abnormal marrow dU suppression pattern; three of nine surgery-only nitrous oxide recipients also had abnormal assays at 24 hours.

    Serum cobalamin concentration → Deoxyuridine suppression assay source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    experimental_model
    Prospective perioperative study in 22 patients undergoing cardiac bypass surgery.
    exposure
    Nitrous oxide/oxygen for 24 hours, during surgery only, or no nitrous oxide; marrow morphology and deoxyuridine suppression assays.
    limitations
    The assay is an indirect functional test, not a direct methionine-synthase rate measurement.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    A normal amount measured in serum did not establish normal intracellular function under this exposure.
    primary_references
    [b12-amess1978] Megaloblastic haemopoiesis in patients receiving nitrous oxide (1978). https://pubmed.ncbi.nlm.nih.gov/79709/ DOI: 10.1016/s0140-6736(78)92941-0
    tissue_or_cell_type
    Human bone marrow and serum
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1722–1732

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Prospective perioperative study in 22 patients undergoing cardiac bypass surgery. · source_derived_draft · unverified_draft

    ### b12-nitrous-oxide-serum-function-discordance Serum B12 remained normal despite the abnormal marrow dU suppression pattern; three of nine surgery-only nitrous oxide recipients also had abnormal assays at 24 hours. Condition category: machinery_impairment nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: A normal amount measured in serum did not establish normal intracellular function under this exposure. organism: Homo sapiens tissue_or_cell_type: Human bone marrow and serum experimental_model: Prospective perioperative study in 22 patients undergoing cardiac bypass surgery. limitations: The assay is an indirect functional test, not a direct methionine-synthase rate measurement. exposure: Nitrous oxide/oxygen for 24 hours, during surgery only, or no nitrous oxide; marrow morphology and deoxyuridine suppression assays. [b12-amess1978] Megaloblastic haemopoiesis in patients receiving nitrous oxide (1978). https://pubmed.ncbi.nlm.nih.gov/79709/ DOI: 10.1016/s0140-6736(78)92941-0
    Complete structured claim and evidence

  2. Twelve of 419 recognized B12-deficient patients had serum cobalamin above 200 pg/mL; five had prominent neurologic involvement that responded to therapy.

    Serum cobalamin concentration → B12-associated neuropsychiatric impairment source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    biomarker_context Imported condition classification; unverified.
    experimental_model
    Maintenance-relapse observations plus a review of 419 recognized B12-deficient patients.
    exposure
    Serum cobalamin, MMA and total homocysteine measurements; clinical response used in diagnosis.
    limitations
    Retrospective diagnostic attribution; no estimate of specificity in unselected patients. Potential cohort overlap with related reports.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    A single circulating B12 measurement is not a complete picture of function.
    primary_references
    [b12-lindenbaum1990] Diagnosis of cobalamin deficiency: II. Relative sensitivities of serum cobalamin, methylmalonic acid, and total homocysteine concentrations (1990). https://pubmed.ncbi.nlm.nih.gov/2339684/ DOI: 10.1002/ajh.2830340205
    tissue_or_cell_type
    Human blood or whole-person endpoints
    trigger_kind
    biomarker_context Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1500–1510

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Maintenance-relapse observations plus a review of 419 recognized B12-deficient patients. · source_derived_draft · unverified_draft

    ### b12-serum-normal-recognized-cases Twelve of 419 recognized B12-deficient patients had serum cobalamin above 200 pg/mL; five had prominent neurologic involvement that responded to therapy. Condition category: biomarker_context nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: A single circulating B12 measurement is not a complete picture of function. organism: Homo sapiens tissue_or_cell_type: Human blood or whole-person endpoints experimental_model: Maintenance-relapse observations plus a review of 419 recognized B12-deficient patients. limitations: Retrospective diagnostic attribution; no estimate of specificity in unselected patients. Potential cohort overlap with related reports. exposure: Serum cobalamin, MMA and total homocysteine measurements; clinical response used in diagnosis. [b12-lindenbaum1990] Diagnosis of cobalamin deficiency: II. Relative sensitivities of serum cobalamin, methylmalonic acid, and total homocysteine concentrations (1990). https://pubmed.ncbi.nlm.nih.gov/2339684/ DOI: 10.1002/ajh.2830340205
    Complete structured claim and evidence

  3. Patients with vitamin B-12 deficiency at study end had a mean homocysteine of 23.7 micromol/l, compared with 18.1 in those with low B-12 and 14.9 in those with normal B-12.

    Serum cobalamin concentration → Human fasting plasma total homocysteine concentration source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    biomarker_context Imported condition classification; unverified.
    evidence_span
    {"source_cache": "artifacts/metformin-research/20488910.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922", "start_char": 0, "end_char": 2518, "text_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922"}
    experimental_model
    Multicentre randomised placebo-controlled trial, 390 people with type 2 diabetes on insulin
    exposure
    850 mg metformin three times daily for 4.3 years versus placebo
    limitations
    The strongest available human causal evidence for the B12 effect. It measured concentrations and deficiency incidence, not clinical deficiency syndromes.
    nutrient_topic
    Metformin research collection; topical membership is not evidence of a direct clinical effect, and pharmacological exposure is not dietary intake. · Metformin
    organism
    Human
    plain_language
    The lower the vitamin, the higher this metabolite climbed.
    primary_references
    [metformin-p20488910] Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial. (2010). https://pubmed.ncbi.nlm.nih.gov/20488910/ DOI: 10.1136/bmj.c2181
    tissue_or_cell_type
    Whole body
    trigger_kind
    biomarker_context Imported condition classification; unverified.

    Metformin: transport, molecular targets, gut mechanisms and nutrient interactions (2026-09-19) · lines 1074–1085

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Multicentre randomised placebo-controlled trial, 390 people with type 2 diabetes on insulin · source_derived_draft · unverified_draft

    ### metformin-b12-homocysteine Patients with vitamin B-12 deficiency at study end had a mean homocysteine of 23.7 micromol/l, compared with 18.1 in those with low B-12 and 14.9 in those with normal B-12. Condition category: biomarker_context nutrient_topic: Metformin research collection; topical membership is not evidence of a direct clinical effect, and pharmacological exposure is not dietary intake. plain_language: The lower the vitamin, the higher this metabolite climbed. organism: Human tissue_or_cell_type: Whole body experimental_model: Multicentre randomised placebo-controlled trial, 390 people with type 2 diabetes on insulin limitations: The strongest available human causal evidence for the B12 effect. It measured concentrations and deficiency incidence, not clinical deficiency syndromes. exposure: 850 mg metformin three times daily for 4.3 years versus placebo evidence_span: {"source_cache": "artifacts/metformin-research/20488910.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922", "start_char": 0, "end_char": 2518, "text_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922"} [metformin-p20488910] Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial. (2010). https://pubmed.ncbi.nlm.nih.gov/20488910/ DOI: 10.1136/bmj.c2181
    Complete structured claim and evidence

What acts on it

  1. Cyanocobalamin increased serum B12 and holotranscobalamin and reduced total homocysteine during the 12-month trial.

    Cyanocobalamin → Serum cobalamin concentration source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    biomarker_context Imported condition classification; unverified.
    experimental_model
    Double-blind randomized trial: 201 adults aged at least 75 with B12 107–210 pmol/L, without anemia or relevant neurologic/cognitive signs; 191 had outcome assessment.
    exposure
    Oral cyanocobalamin 1 mg/day versus placebo for 12 months.
    limitations
    Blood responses do not establish delivery or functional recovery in every tissue.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    The tablets changed the biochemical measurements.
    primary_references
    [b12-dangour2015] Effects of vitamin B-12 supplementation on neurologic and cognitive function in older people: a randomized controlled trial (2015). https://pubmed.ncbi.nlm.nih.gov/26135351/ DOI: 10.3945/ajcn.115.110775
    tissue_or_cell_type
    Human blood or whole-person endpoints
    trigger_kind
    biomarker_context Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1512–1522

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Double-blind randomized trial: 201 adults aged at least 75 with B12 107–210 pmol/L, without anemia or relevant neurologic/cognitive signs; 191 had outcome assessment. · source_derived_draft · unverified_draft

    ### b12-dangour-status-response Cyanocobalamin increased serum B12 and holotranscobalamin and reduced total homocysteine during the 12-month trial. Condition category: biomarker_context nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: The tablets changed the biochemical measurements. organism: Homo sapiens tissue_or_cell_type: Human blood or whole-person endpoints experimental_model: Double-blind randomized trial: 201 adults aged at least 75 with B12 107–210 pmol/L, without anemia or relevant neurologic/cognitive signs; 191 had outcome assessment. limitations: Blood responses do not establish delivery or functional recovery in every tissue. exposure: Oral cyanocobalamin 1 mg/day versus placebo for 12 months. [b12-dangour2015] Effects of vitamin B-12 supplementation on neurologic and cognitive function in older people: a randomized controlled trial (2015). https://pubmed.ncbi.nlm.nih.gov/26135351/ DOI: 10.3945/ajcn.115.110775
    Complete structured claim and evidence

  2. Over 4.3 years, metformin lowered B12 concentration by 19% relative to placebo and increased the absolute risk of B12 below 150 pmol/L by 7.2 percentage points (95% CI 2.3–12.1).

    Metformin → Serum cobalamin concentration source_derived_draftungraded
    Experimental context and source evidence
    experimental_model
    Multicenter randomized placebo-controlled trial: 390 insulin-treated patients with type 2 diabetes.
    exposure
    Metformin 850 mg three times daily versus placebo for 4.3 years; historical experimental exposure.
    limitations
    Insulin-treated type 2 diabetes; does not directly establish the absorption mechanism or a neurologic outcome.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Long-term metformin exposure increased biochemical B12 deficiency in this trial.
    primary_references
    [b12-dejager2010] Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial (2010). https://pubmed.ncbi.nlm.nih.gov/20488910/ DOI: 10.1136/bmj.c2181
    tissue_or_cell_type
    Human blood or whole-person endpoints

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1624–1634

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Multicenter randomized placebo-controlled trial: 390 insulin-treated patients with type 2 diabetes. · source_derived_draft · unverified_draft

    ### b12-metformin-randomized-status Over 4.3 years, metformin lowered B12 concentration by 19% relative to placebo and increased the absolute risk of B12 below 150 pmol/L by 7.2 percentage points (95% CI 2.3–12.1). Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Long-term metformin exposure increased biochemical B12 deficiency in this trial. organism: Homo sapiens tissue_or_cell_type: Human blood or whole-person endpoints experimental_model: Multicenter randomized placebo-controlled trial: 390 insulin-treated patients with type 2 diabetes. limitations: Insulin-treated type 2 diabetes; does not directly establish the absorption mechanism or a neurologic outcome. exposure: Metformin 850 mg three times daily versus placebo for 4.3 years; historical experimental exposure. [b12-dejager2010] Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial (2010). https://pubmed.ncbi.nlm.nih.gov/20488910/ DOI: 10.1136/bmj.c2181
    Complete structured claim and evidence

  3. Compared with placebo, metformin treatment was associated with a mean decrease in vitamin B-12 concentration of 19% over 4.3 years.

    Metformin → Serum cobalamin concentration source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    nutrient_deficiency Imported condition classification; unverified.
    evidence_span
    {"source_cache": "artifacts/metformin-research/20488910.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922", "start_char": 0, "end_char": 2518, "text_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922"}
    experimental_model
    Multicentre randomised placebo-controlled trial, 390 people with type 2 diabetes on insulin
    exposure
    850 mg metformin three times daily for 4.3 years versus placebo
    limitations
    The strongest available human causal evidence for the B12 effect. It measured concentrations and deficiency incidence, not clinical deficiency syndromes.
    nutrient_topic
    Metformin research collection; topical membership is not evidence of a direct clinical effect, and pharmacological exposure is not dietary intake. · Metformin
    organism
    Human
    plain_language
    Years of the drug lower the vitamin in blood.
    primary_references
    [metformin-p20488910] Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial. (2010). https://pubmed.ncbi.nlm.nih.gov/20488910/ DOI: 10.1136/bmj.c2181
    tissue_or_cell_type
    Whole body
    trigger_kind
    nutrient_deficiency Imported condition classification; unverified.

    Metformin: transport, molecular targets, gut mechanisms and nutrient interactions (2026-09-19) · lines 1035–1046

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Multicentre randomised placebo-controlled trial, 390 people with type 2 diabetes on insulin · source_derived_draft · unverified_draft

    ### metformin-b12-decrease Compared with placebo, metformin treatment was associated with a mean decrease in vitamin B-12 concentration of 19% over 4.3 years. Condition category: nutrient_deficiency nutrient_topic: Metformin research collection; topical membership is not evidence of a direct clinical effect, and pharmacological exposure is not dietary intake. plain_language: Years of the drug lower the vitamin in blood. organism: Human tissue_or_cell_type: Whole body experimental_model: Multicentre randomised placebo-controlled trial, 390 people with type 2 diabetes on insulin limitations: The strongest available human causal evidence for the B12 effect. It measured concentrations and deficiency incidence, not clinical deficiency syndromes. exposure: 850 mg metformin three times daily for 4.3 years versus placebo evidence_span: {"source_cache": "artifacts/metformin-research/20488910.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922", "start_char": 0, "end_char": 2518, "text_sha256": "6c9e09d44fe1103e6927321e925e69e31c38d1a688fd2ac18ea96927098de922"} [metformin-p20488910] Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial. (2010). https://pubmed.ncbi.nlm.nih.gov/20488910/ DOI: 10.1136/bmj.c2181
    Complete structured claim and evidence

In the sources

Preserved passages that mention this component, quoted exactly. Open one to read it in context.

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