What is the ideal sodium and potassium intake in the context of cardiovascular health?

Over the past 40 years, we have frequently assessed the association of blood pressure (BP) and the risk of hypertension with the 24-h urinary excretion of sodium and potassium in randomly selected individuals, representative of populations of different ethnicity.1 A consistent finding throughout all analyses was that the associations of BP with 24-h urinary sodium (UVNA) were weak and nonsignificant, whereas higher 24-h potassium excretion (UVK) was related to lower BP and smaller risk of hypertension, irrespective of the level of adjustment for confounders. In 2011, we analysed families randomly enrolled in the Flemish Study on Genes, Environment and Health Outcomes (1985–2004) and in the European Project on Genes in Hypertension (1999–2001).1 This prospective cohort study included 3681 participants without cardiovascular disease, of whom 1499 had their BP and UVNA measured at baseline and follow-up (2005–2008). Over 7.9 years (median) of follow-up, cardiovascular mortality decreased across increasing tertiles of UVNA (mean 2.5, 3.9, and 6.0 g/day) from 50 to 24 and to 10 deaths, respectively, resulting in rates (Figure 1) of 4.1% (95% confidence interval: 3.5–4.7%), 1.9% (1.5–2.3%), and 0.8% (0.5–1.1%). In 1499 participants followed for 6.1 years, systolic BP increased by 0.37 mmHg per year, whereas UVNA did not change. In all our studies, dietary sodium and potassium intake were assessed by exactly timed 24-h urine collections, for which we set and validated quality standards, based on volume and the sex-specific creatinine excretion.1 Given the complexity in obtaining high-quality 24-h urine samples, many studies relied on spot urines2,3 to compute the daily salt intake, most often by the Kawasaki formula, which has been criticized4 but represents a practicable approach certainly in large cohort studies. Dietary sodium and potassium intake are characterized by large diurnal and seasonal intraindividual variation, so that multiple urine collections are required to characterize a person’s dietary habits. However, irrespective of the methods applied, urine collections can accurately assess sodium and potassium intake at the group or population level.