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Open WellbeingWhat the studies actually measured

Energy and exercise

Ironand Fatigue

Only one source here so far, and it measured lower fatigue.

How sure anyone can be

High certainty, level 4 of 4

Further research is very unlikely to change this.

The numbers reported

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

-0.52-0.38 standardised effect size-0.23

This range stays on one side of the no-difference line.

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 · 714 participants

    High certainty, level 4 of 4

    Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials.

    BMJ Open. 2018;8(4):e019240. doi:10.1136/bmjopen-2017-019240. PMID:29626044.

    Number reported
    -0.38 standardised effect size
    Which way it went
    Lower
    Likely range
    -0.52 to -0.23
    Source’s own words
    standardised mean difference in self-reported fatigue vs comparator
    Who was studied
    Adult with iron deficiency non anaemic
    Compared with
    placebo or active therapy
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    I2 0%
    Kind of record
    Journal article
    How this rating was reachedstarts at High, and nothing brought it down
    1. Starts at High
    2. Ends at HighNothing brought this one down a step.
    Checked, nothing to step it down for
    risk of bias, indirectness and imprecision
    Inconsistency
    No high disagreement reported between the 4 studies it pooled

    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 Iron

Nine of the 18 things on our list for Iron have no reading here yet:

  • Bloating Symptom Severity Score
  • Endurance Performance (Time to Exhaustion)
  • Fractional iron absorption
  • Heart rate variability (RMSSD)
  • Hematocrit
  • Serum iron
  • Six-Minute Walk Test Distance
  • Soluble Transferrin Receptor (sTfR)
  • Total Iron Binding Capacity

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.