If you thought that another very large clinical trial would finally settle uncertainties about salt — well, I hate to disappoint you. Opinions about the role of salt in cardiovascular disease range from “there is little relationship” to “the relationship is strong and consistent,” with all sorts of conjecture in between.
Mente et al report on data obtained from 18 different countries in which a single morning urine specimen measurement of sodium and potassium was used as a metric for dietary ingestion of those same electrolytes. They found a positive linear relationship between salt ingestion and blood pressure (BP), such that every 1 g/d increase in sodium was associated with a 2.11 mmHg increase in SBP.
Their data did not, however, demonstrate a “one size fits all” linearity. Persons with the highest sodium ingestion (> 5 g/d) demonstrated an almost 4-fold greater increment in BP per gram of sodium consumption than persons at the lowest levels (< 3 g/d sodium). Also, older persons and persons with pre-existing hypertension were more sensitive to BP-raising effects of sodium.
Potassium ingestion was inversely associated with BP. So are we finally finished with this roller coaster-like journey about sodium? Yes — well, that is until you turn the page on that article in the New England Journal of Medicine to find that the very next article also examined sodium in more than 100,000 persons, and did not come up with the same answer — oh well, we’ll keep searching.
Source: Mente A, et al. N Engl J Med 2014;371:601-611.