Each LDL (and VLDL/IDL) particle carries exactly one apolipoprotein B molecule, so plasma apoB concentration is a direct count of atherogenic particle number, whereas LDL-cholesterol can rise either because there are more particles or because each particle is more cholesterol-enriched. Those two routes differ in atherogenicity: particle number (apoB) is the more consistent predictor of cardiovascular risk, since it is the particle count entering and being retained in the arterial wall that drives atherogenesis. In this trial LDL-cholesterol and apoB rose together (apoB +~10% from 0 to 4 eggs, correlated with the cholesterol changes), so the dietary-cholesterol effect is carried by an increase in particle number, not by cholesterol-enrichment of a fixed particle pool. This upgrades the bare LDL-cholesterol slope into a claim that egg cholesterol adds genuinely atherogenic particles, strengthening the dose-response hypothesis’s clinical relevance. The step is not automatic — LDL-C can move without apoB — which is exactly why the observed apoB co-movement is informative rather than trivial.
Validity (step 6)
status: approved — reason_if_not_false: checked. Traced the step; it is near-definitional given standard biochemistry. Premise: each apoB-lipoprotein particle (VLDL/IDL/LDL) carries exactly one apoB molecule, so plasma apoB concentration IS a count of atherogenic particles. Therefore a measured ~10% apoB rise entails a ~10% rise in particle number — the “raises particle number” clause follows directly. The “not merely cholesterol per particle” clause also holds arithmetically: cholesterol-per-particle ∝ LDL-C/apoB, and since apoB rose ~in step with LDL-C, that ratio is roughly unchanged, so the LDL-C rise is carried by particle number rather than enrichment. Probed for undercutting defeaters conditional on premises: (i) the apoB rise could reflect VLDL/IDL rather than LDL specifically — but the conclusion is about apoB-particle number broadly, and the reported correlation with LDL-C changes ties it to LDL; either way particle number rose. (ii) “atherogenically meaningful rather than cosmetic” is a mild evaluative addendum, but it rests on the stated premise that particle number (apoB) is the more consistent CVD predictor, which is granted here (its truth is priced downstream, not as validity). No defeater breaks the reason→conclusion link. Approved as stated.