I suggest measuring urinary sodium excretion in 24 hours. In a patient with steady renal function and global state, even in case of tubulopathies with altered sodium management, this would represent the sodium intake . The kidney gets rid of the excess (it is a simple way to express it). In tubulopathies, obviously, the excretion could be high due to the inability of retaining sodium but it would represent sodium intake as the patient needs a higher one to keep homeostasis.

Probably I support the proposed method by Javier: it's to difficult to estimate salt consumption precisely in routine practice. The object (human) should be monitoring for a long time with numerous calculations of liquid/food type and quantity with account of known salt content in each consuming ingredient that de facto unlikely feasibly to assess in ambulatoty settings.

The patient or his/her relatives should use raw (whole) foods and salt amount in each prepared food should be calculated closely given amount and percentage of added natrium chloride. Even row foods contain different amounts of natural sodium (mammee apple, applesauce, dried apples, cranberry sauce, cardoon, etc). Beets, carrots, seaweed, turnips, beet greens, celery and chard contain 75 mg of sodium or more per serving. Other raw products contains sodium as well particularly barn door fowl and meat. One chicken egg contains appr. 140 mg and one glass of fresh skimmed milk (230 ml) - 50 mg of sodium. It should be noted that many liquids contain sodium, e.g. soda, mineral water, etc and some ingested preparations (e.g. Gaviscon, Peptac, etc).

So, the precise calculation of sodium intake is very complex and laborious task since measuring of urinary sodium excretion may represent a simplified and integral method of sodium consumption estimation.

Although laborious, 24 h urinary collection is the most exact method. You can try food diary but you never know the salt content of the food that the subject cooks himself or herself - except when he or she adds no salt into it. Food diary can be a good method for limiting the salt intake of the subject, as well as the intake of animal fat and fast absorbing carbohydrates.

Thanks everyone. I was also wondering how a spot urine Na/K and/or spot urine Na/Cr ratio may compare with the "gold standard" 24 hour urine Na collection, considering the practical difficulties of doing 24 hr urine collections in the ambulatory setting.

Genetic defect of Low Red Blood Cell Potassium is presented in every hypertensive patient as well as 56% of their normotensive (NT) siblings and 33% of NT offspring. Since RBCs are the key regulator of cellular K and Body-K homeostasis, confirmed by our Laboratory (1976), a defective low RBC-K is associated with impaired large renal tubular water excretion (>1.2 ml/min, nocturnal) and K excretion. So, best evaluations are fasting plasma/RBC/Urine Electrolytes (Na, K, Cl, Ionized Ca++), with urine sample from 12-hours night (7 amd-7 pm), particularly the higher plasma Cl (>112 mmol/l) and RBC Cl (>87 mmol/l) in essential hypertension, which provides strong evidence for Salt restriction (NaCl) in essential hypertension and new "salting" preparation free of Chloride.

That's interesting. Thanks, Antonio.