Two facts have to be combined. First, in a majority of periods (69%) added dietary cholesterol produced little plasma change, and this coincided with measured down-regulation of fractional absorption and/or endogenous synthesis. Second, wherever plasma cholesterol did rise, it rose in exactly the periods where endogenous synthesis was NOT suppressed.
If the split were only measurement noise or regression to the mean, the plasma rise would not be systematically tied to a specific measured physiological state (unsuppressed synthesis); noise would scatter the rise across compensating and non-compensating periods alike. The observed alignment — rise ←> failed suppression, flat ←> successful suppression — is what a genuine feedback-control mechanism predicts and what pure variability does not. This upgrades the bare 69/31 frequency into evidence for (a) a real buffering mechanism operating through absorption/synthesis feedback (H-2) and (b) an individualized responder axis, since the mechanism succeeds in most people and fails in a minority (H-1). The inference is not airtight — the design measures synthesis in circulating leukocytes as a proxy for whole-body synthesis, and per-period rather than per-subject accounting leaves open how stable the phenotype is — but the mechanistic co-alignment is the non-obvious step that the raw split alone does not give.
Validity (step 6)
status: corrected, reason_if_not_false: checked.
Traced step. The load-bearing move is: a plasma rise that aligns systematically with one measured physiological state (unsuppressed synthesis) is what a feedback-control mechanism predicts and what noise/regression-to-mean does not (noise would scatter the rise across compensating and non-compensating periods alike). That step is sound — systematic tie of an outcome to a specific measured intermediate is genuine evidence for a mechanism over random variation. So the mechanism half of the conclusion (H-2, a real absorption/synthesis buffering mechanism) is approved as stated.
Where the as-stated claim over-reaches is the individualized responder axis / “governing who responds” half (H-1). O-1/O-2 are counted per diet-period, not per subject. An undercutting defeater survives without denying the premises: within-person, state-dependent variation in synthesis suppression (a person compensating in some periods and not others) reproduces the exact rise↔failed-suppression alignment with no stable person-level responder phenotype. The per-period design cannot separate a trait (who responds) from a state (when suppression happens to fail) — a limitation the body already concedes. Hence the step supports the mechanism but only weakly supports, and does not establish, individualization. Corrected to the weaker form; statement edited, pre-edit text preserved below.
Original
statement: “The plasma-cholesterol rise appearing specifically where synthesis suppression failed, set against a 69% compensating majority, supports an individualized feedback-control mechanism (not mere random variation) governing who responds to dietary cholesterol.”