Validation of Simplified Tools for Assessment of Sodium Intake in Iranian Population: Rationale, Design and Initial Findings

The 24-hour urine sodium excretion is considered the gold standard method to estimate salt intake. However, since this method is not easy to perform, this study developed two instruments, including a semi-quantitative food frequency questionnaire (FFQ) and one spot urine sodium excretion, to assess sodium intake. These two methods were then compared with 24-h urine sodium excretion and twelve 24-h recalls during a year.

This study was performed on 219 healthy subjects aged ≥ 6 years in 2014-2015. The FFQ was completed twice, at baseline and one year thereafter, to examine the reproducibility of the FFQ. The validity of three spot urine sodium excretions in the morning, afternoon, and evening and FFQ for the assessment of sodium intake were compared against the 24-h urine sodium excretion method. Moreover, the validity of FFQ was examined against 24-h dietary recalls for the assessment of total sodium consumption and contribution of food groups to sodium intake. The content validity of the FFQ was estimated by an expert panel including 10 nutritionists.

Based on their nutrients, the final food items were categorized into 11 groups including: 1) dairy products, 2) fruits, 3) vegetables, 4) meat and egg, 5) grains and legumes, 6) mixed dishes, prepared foods, and restaurant foods, 8) nuts and seeds, 8) oils and fats, 9) sauces and desserts, 10) drinks, and 11) others.

Spot urine and a specific FFQ comprising 136 items were used to develop a method for the assessment of sodium intake and contribution of foods to its intake among the Iranian population. This method can be used in large-scale population studies at the national level.