Does Tracey Marks recommend Vitamin B12?
Tracey Marks recommends Vitamin B12 in some contexts, but has also raised cautions.
Published research rates it strong evidence. Of Tracey Marks's 118 tracked claims, 55 are supported or partially supported by studies on PubMed.
Evidence last reviewed May 2026
Tracey Marks on Vitamin B12 β 118 claims
βFor patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.β
For patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.
None of the 10 retrieved studies directly address the use of methylcobalamin or other active B vitamin forms specifically in patients with MTHFR genetic variants. The available literature focuses on Bβ¦
βI don't rely on symptoms alone β I check serum B12 and homocysteine levels.β
Marks checks both serum B12 and homocysteine levels rather than relying on symptoms alone.
The recommendation to use both serum B12 and homocysteine as diagnostic markers aligns with general clinical practice principles discussed in B12 deficiency literature (e.g., PMID 34046142, PMID 40961β¦
βThe populations I routinely screen include older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.β
Marks routinely screens for B12 deficiency in older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.
The screening populations Marks identifies (older adults, metformin users, PPI users, vegans/vegetarians, and those with psychiatric or cognitive complaints) align with well-established risk groups foβ¦
βMethylmalonic acid is another sensitive functional marker I use in ambiguous cases.β
Methylmalonic acid is another sensitive functional marker for B12 status that Marks uses in ambiguous cases.
None of the 10 provided studies contain extractable key findings that directly address the use of methylmalonic acid (MMA) as a functional biomarker for B12 status in clinical decision-making. While sβ¦
βI don't rely on symptoms alone β I check serum B12 and homocysteine levels.β
Marks checks both serum B12 and homocysteine levels rather than relying on symptoms alone.
None of the 10 provided studies directly address the diagnostic recommendation of combining serum B12 testing with homocysteine measurement rather than relying on symptoms alone. The studies cover topβ¦
βI don't rely on symptoms alone β I check serum B12 and homocysteine levels.β
Marks checks both serum B12 and homocysteine levels rather than relying on symptoms alone.
None of the 10 provided studies directly evaluate the diagnostic practice of measuring both serum B12 and homocysteine levels as a clinical strategy, nor do they compare this dual-marker approach agaiβ¦
βFor patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.β
For patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.
None of the 10 provided studies directly address MTHFR genetic variants or the comparative efficacy of methylcobalamin versus cyanocobalamin in this population. The closest relevant study (PMID 328681β¦
βThe populations I routinely screen include older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.β
Marks routinely screens for B12 deficiency in older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.
The expert's screening recommendations for B12 deficiency align with broadly accepted clinical rationale, and several studies in the provided list address relevant populations and outcomes. Reviews onβ¦
βMethylmalonic acid is another sensitive functional marker I use in ambiguous cases.β
Methylmalonic acid is another sensitive functional marker for B12 status that Marks uses in ambiguous cases.
None of the 10 provided studies directly address the use of methylmalonic acid (MMA) as a functional biomarker for assessing B12 status in clinical practice. While several studies touch on B12 deficieβ¦
βFor patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.β
For patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.
None of the 10 published studies provided directly address MTHFR genetic variants or the comparative efficacy of active B vitamin forms (e.g., methylcobalamin vs. cyanocobalamin) in individuals with tβ¦
βThe populations I routinely screen include older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.β
Marks routinely screens for B12 deficiency in older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.
The screening populations Marks identifies (older adults, metformin users, PPIs users, vegans/vegetarians, and those with psychiatric/cognitive complaints) align with well-established clinical risk faβ¦
βMethylmalonic acid is another sensitive functional marker I use in ambiguous cases.β
Methylmalonic acid is another sensitive functional marker for B12 status that Marks uses in ambiguous cases.
None of the 10 provided studies directly address methylmalonic acid (MMA) as a functional biomarker for assessing B12 status. While some review articles (e.g., PMIDs 27916823 and 34046142) may discussβ¦
βMethylmalonic acid is another sensitive functional marker I use in ambiguous cases.β
Methylmalonic acid is another sensitive functional marker for B12 status that Marks uses in ambiguous cases.
None of the 10 provided studies directly address the use of methylmalonic acid (MMA) as a functional biomarker for B12 status assessment. While several studies involve B12 deficiency diagnosis and supβ¦
βThe populations I routinely screen include older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.β
Marks routinely screens for B12 deficiency in older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.
The expert's screening recommendations align with well-established clinical risk factors for B12 deficiency, and several studies in the provided list address relevant populations (e.g., PMID 27916823β¦
βFor patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.β
For patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.
None of the 10 provided studies directly address the claim that individuals with MTHFR genetic variants benefit specifically from active B vitamin forms such as methylcobalamin. The closest relevant sβ¦
βI don't rely on symptoms alone β I check serum B12 and homocysteine levels.β
Marks checks both serum B12 and homocysteine levels rather than relying on symptoms alone.
None of the 10 provided studies directly address the diagnostic recommendation of using combined serum B12 and homocysteine testing rather than relying on symptoms alone. The studies cover topics suchβ¦
βFor patients with genetic variants in the MTHFR enzyme, active forms of B vitamins including methylcobalamin may be more appropriate.β
For patients with MTHFR genetic variants, active forms of B vitamins including methylcobalamin may be more appropriate.
None of the 20 studies provided directly examine the use of methylcobalamin or other active B vitamin forms specifically in patients with MTHFR genetic variants. While PMID 24494987 and 32868164 discuβ¦
βI don't rely on symptoms alone β I check serum B12 and homocysteine levels.β
Marks checks both serum B12 and homocysteine levels rather than relying on symptoms alone.
The literature supports the clinical rationale for using homocysteine as a functional biomarker alongside serum B12. PMID 33809274 (systematic review/meta-analysis of RCTs) notes that B12 complaints aβ¦
βThe populations I routinely screen include older adults over 60, anyone on metformin (which reduces B12 absorption), anyone on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints.β
The expert routinely screens older adults over 60, people on metformin, people on proton pump inhibitors, all vegans and vegetarians, and anyone presenting with depression, anxiety, or cognitive complaints for B12 deficiency.
The expert's screening recommendations align well with the published evidence across multiple study types. PMID 40961307 (review) directly identifies metformin use, proton pump inhibitors, older age,β¦
βMethylmalonic acid is another sensitive functional marker I use in ambiguous cases.β
Methylmalonic acid is another sensitive functional marker the expert uses in ambiguous B12 cases.
The review on Vitamin B12 Deficiency (PMID: 40961307) acknowledges the complexity of B12 deficiency diagnosis and mentions functional markers indirectly through discussion of deficiency symptoms and rβ¦
Other supplements Tracey Marks discusses
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