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Open WellbeingWhat the studies actually measured

Vitamin and mineral levels

Vitamin B12and Hemoglobin

Only one source here so far, and it found no clear difference in hemoglobin.

How sure anyone can be

Low certainty, level 2 of 4

Further research is likely to change this.

The numbers reported

One source’s range, drawn against its own line of no difference and scaled to its own numbers.

-0.1900.18

This range crosses the no-difference line, so these numbers fit a real difference and no difference at all equally well.

Bar the confidence interval — the range the true effect is likely to sit inNotch the number the source reportedLine where there would be no difference at all

One source, newest first

What we read is the published abstract, not the full paper, so a blank below may still be printed in the paper itself. A fixed rule worked this out from the source’s own fields. Nobody checked this rating by hand.

  • Systematic review, 2018 · 4 studies pooled · 343 participants

    Low certainty, level 2 of 4

    The effect of vitamin B12 and folic acid supplementation on routine haematological parameters in older people: an individual participant data meta-analysis.

    Eur J Clin Nutr. 2018;72(6):785-795. doi:10.1038/s41430-018-0118-x. PMID:29520083.

    Number reported
    0
    Which way it went
    No clear difference
    Likely range
    -0.19 to 0.18
    Source’s own words
    g/dL haemoglobin, change vs placebo
    Who was studied
    Older adult
    Compared with
    placebo
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    Not in the abstract
    Kind of record
    Journal article
    How this rating was reachedstarts at High, 2 steps down: risk of bias and imprecision
    1. Starts at High
    2. Risk of bias brought it down to Moderatethe abstract reports no risk-of-bias or quality appraisal, so study limitations cannot be ruled outNot in the abstract
    3. Imprecision brought it down to Lowthe confidence interval includes no effectReported in the abstract
    4. Ends at Low2 steps down.
    Checked, nothing to step it down for
    indirectness
    Inconsistency
    No high disagreement reported between the 4 studies it pooled

    Imprecision stops at the first check that applies; others may apply too.

    AI-reviewed & signed — an AI agent re-read this finding against the saved source and checked that the quote, the numbers, the units and the direction match it. No person read it. The owner authorised the agent to sign the batch with the owner's key, and every build rechecks that signature against these exact bytes.

    Read the abstract on PubMed

What is still missing from these readings

  • Amount taken — Not in the abstract.
  • For how long — Not in the abstract.

Something nobody wrote down is never a zero and never a guess.

Still to read for Vitamin B12

Eight of the 16 things on our list for Vitamin B12 have no reading here yet:

  • Brain Atrophy Rate (MRI Volume Loss)
  • Holotranscobalamin (active B12)
  • Methylmalonic acid (MMA)
  • Muscle strength (1-RM)
  • Sleep onset latency
  • Total sleep time
  • Vitamin B12
  • Wake after sleep onset (WASO)

Still to read means nobody here has got to it, not that it was tried and did nothing or that no research exists. A pairing on no list is not a gap: we never set out to read it.

Read next

This is a library, not advice. No recommendation, no dose, no diagnosis, no ranking. We never ask about your symptoms, and nothing here is tailored to you.