Following on from KevinCompounds — and this may be the naive question:
Was that from a primary source or from a summary of one?
OP back with an update, since a thread like this is useless without one.
Closing the loop. The answer turned out to depend on the detail I had left out of the opening post, which is a lesson about how to ask rather than about the subject.
hank_denver said:Worth stating the units and the reference range whenever you post a number here.
Right, and the exception is worth naming rather than left implied, because the exception is where people get into trouble.
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference Standardshank_denver said:Worth stating the units and the reference range whenever you post a number here.
Saving this. It is the first explanation that did not require me to already understand it. Sending this to two other people who asked me the same thing last week.
From the other side of the consultation, briefly. The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either. Those three things can all be true at once, and most arguments here are two people holding different parts of that.