Zinc lozenges under about 75 mg a day did nothing in any trial
Five trials tested lozenges under that mark and every one came back empty. Above it, the same review found colds running roughly a fifth to two fifths shorter.
What the study found
Below about 75 mg a day, zinc lozenges did nothing at all
Five trials tested lozenges under that mark and every one came back empty. Above it, the same review found colds running roughly a fifth to two fifths shorter. The line is a floor rather than a slope: crossing it appears to matter, and climbing further above it does not.
The caveat · Line drawn after seeing the data
The 75 mg line was drawn after looking at the data rather than set in advance, so it explains the same trials it came from. Five trials below it and eight above is a thin basis for a threshold. Both reviews behind it have the same single author, whose complaint is what got the competing Cochrane review withdrawn.
What we don't know
The 75 mg line was drawn after looking at the data rather than set in advance, so it explains the same trials it came from. Five trials below it and eight above is a thin basis for a threshold. Both reviews behind it have the same single author, whose complaint is what got the competing Cochrane review withdrawn.