Dietary surveys (using questionnaires) and the collection of urine samples are the two best methods and they are probably the most commonly used.
-Dietary surveys are easier to carry out and most people are able to complete them; however, they might involve reporting inaccuracies.
-24-hour urine collection is considered to be the 'gold standard'. Under resting conditions it represents roughtly 85-90% of the ingested sodium. This method has the advantage of being unaffected by subjective reporting, but urine collection must be accurately timed and requires considerable analytical support.