B12 and the placebo lifted fatigue by the same amount
In 95 people with disabling tiredness and normal B12 levels, eight weeks of 1000 micrograms a day and a placebo each improved fatigue by about eight points.
What the study found
Eight weeks of B12 moved fatigue no more than a placebo did
Everyone in it had disabling tiredness, normal blood B12, and either irritable bowel syndrome or inflammatory bowel disease. They took 1000 micrograms of B12 a day or a placebo, and both groups improved by about eight points. A null in 95 unusual patients settles very little.
The caveat · A low 150 cut-off for normal B12
Both arms improved by roughly eight points, a large placebo response that leaves little room to detect a small real benefit. The bar for normal B12 was set at 150 pmol/L, low enough that some participants may have been functionally short despite passing it.
What we don't know
Both arms improved by roughly eight points, a large placebo response that leaves little room to detect a small real benefit. The bar for normal B12 was set at 150 pmol/L, low enough that some participants may have been functionally short despite passing it.