Comparison of three methods for estimating daily individual discretionary salt intake: 24 hour recall, duplicate-portion method, and urinary lithium-labelled household salt excretion.

OBJECTIVE

To compare methods for estimating discretionary salt intake, that is, salt added during food preparation and consumption in the home.

SETTING

The study was carried out in a rural Guatemalan village.

SUBJECTS

Subjects were selected non-randomly, based on their willingness to cooperate. Nine mother-son dyads participated; the sons were aged 6-9 y.

INTERVENTIONS

Three approaches for estimating the discretionary salt consumption were used: 24 h recall; collection of duplicate portions of salt; and urinary excretion of lithium during consumption of lithium-labelled household salt. Total salt intake was assessed from the excretion of chloride over 24 h.

RESULTS

The mean discretionary salt consumption based on lithium excretion for mothers was 3.9+/-2.0 g/d (mean +/- s.d.) and for children 1.3+/-0.6 g/d. Estimates from the 24 h recalls and from the duplicate portion method were approximately twice and three times those measured with the lithium-marker technique respectively. The salt intake estimated from the recall method was associated with the lithium-marker technique for both mothers and children (Spearman correlation coefficient, 0.76 and 0.70 respectively). The mean daily coefficient of variation in consumption of discretionary salt measured by the three methods, for mothers and boys respectively, were: lithium marker, 51.7 and 43.7%; 24 h recall, 65.8 and 50.7%; and duplicate portion, 51.0 and 62.6%.

CONCLUSIONS

We conclude that an interview method for estimating discretionary salt intake may be a reasonable approach for determining the relative rank-order in a population, especially among female food preparers themselves, but may grossly overestimate the actual intake of salt added during food preparation and consumption.