What methods have been used to estimate salt intake? A systematic review

The relationship between salt intake and cardiovascular diseases is a contemporary scientific controversy, which has been attributed to the limits of the measures of salt intake used in the studies. Thus, this article sought to systematically review the literature on the methods used to estimate salt intake in different study designs. Of the 124 articles, 60.5% used only biochemical measures, 26.6% only self-report measures and 12.9% reported the combined use of both methods. The 24-hour urinary sodium excretion was the predominant biochemical method (79.1%) and the Food Frequency Questionnaire was the predominant self-report measure (36.4%). Interventional studies used mostly 24-hour urinary sodium excretion; while longitudinal studies used self-report measures. The question guiding the study and its design, as well as constraints related to costs, sample size and feasibility seems to influence the choice of the type of measurement.