Commentary: Strength and importance of the relation of dietary salt to blood pressure

Geoge Davey Smith and Andrew Phillips raise some issues concerning methods used in correcting for regression dilution in Intersalt but offer no judgment on the crucial issue of the strength and importance of the relation of dietary salt to blood pressure. To assess this matter properly, in the context of Intersalt findings, three judgments must be made: firstly, on the aetiological significance of the salt-blood pressure relation; secondly, on the probable underestimate of the size of this relation in Intersalt analyses of individuals; and thirdly, on the soundness of Intersalt's updated estimates “revisiting” the strength of this relation, both from its within population and its cross population analyses.1 Davey Smith and Phillips deal not at all with the first and second of these points, and only partially and inconsistently with the third. Much of their commentary deals with generalities, not with specifics of the salt-blood pressure relation and Intersalt results. As a consequence, their commentary neither sheds light on the substantive matter nor contributes positively to public policy.