What are the sodium intake recommendations for the treatment of hypercalciuria in children?

Updated: Apr 23, 2019
  • Author: Stephen W Leslie, MD, FACS; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

A high sodium intake promotes various effects that enhance urinary calcium excretion and increase overall kidney stone formation rates. These effects include a rise in urinary pH, as well as in urinary calcium and cystine levels, and a decrease in urinary citrate excretion. Sodium and calcium share common sites for reabsorption in the renal tubules.

Urinary calcium levels

In healthy adults, high sodium intake has been associated with increased fractional intestinal calcium absorption and a rise in PTH and vitamin D-3 levels. Each 100-mEq increase in daily dietary sodium raises the urinary calcium level by about 50 mg.

Enhanced renal calcium excretion from high dietary sodium consumption is thought result from an increase in extracellular fluid volume, which ultimately results in inhibition of renal tubular calcium reabsorption.

Sodium intake among stone formers has been found to be equal to or higher than the intake in control groups of non–stone formers. Moreover, patients with recurrent nephrolithiasis and hypercalciuria have been found to be particularly sensitive to the hypercalciuric actions of a high-sodium diet.

Urinary pH levels

The rise in urinary pH is caused by an increase in serum and urinary bicarbonate levels. High serum bicarbonate lowers urinary citrate excretion by a direct effect on citrate metabolism in proximal renal tubular cells.

Dietary sodium reduction

Dietary sodium reduction has been shown to decrease urinary calcium excretion in stone formers with hypercalciuria, whereas high dietary sodium is associated with increased urinary calcium excretion and low bone density. (In postmenopausal women, high sodium intake has been directly associated with low bone density in calcium-stone formers.)

Patients should be aware that most restaurant meals and fast food items, such as pizza, contain a considerable amount of sodium. In addition, ketchup, mustard, teriyaki sauce, Worcestershire sauce, soy sauce, canned soups, cold cuts, prepared vegetables, and TV dinners have large amounts of sodium. However, many prepared foods have low-sodium varieties available.

Daily dietary salt intake should be restricted to levels sufficient to keep the urinary sodium excretion below 150-200 mEq/day. Most experts recommend limiting dietary sodium (salt) in calcium-stone formers to about 100 mEq/day, but this is difficult because many people find that salt enhances the taste of food. In children, a good target range for dietary sodium intake is 2-3 mEq/kg/day.

Recommendations to reduce sodium (salt) intake include the following:

  • Remove the saltshaker from the dining table; other spices, such as pepper, salt substitutes, or Mrs. Dash, can be used instead

  • Use little or no salt in food preparation or cooking

  • Avoid eating foods with high salt content whenever possible; most fast food is high in sodium.

  • Do not add any additional salt to foods that already contain it; this would apply to most prepared or canned foods, such as soups, gravies, TV dinners, and canned vegetables

  • Use fresh or frozen vegetables whenever possible; to reduce the salt content of canned vegetables, they should be drained and then rinsed with water before cooking

  • Use one half or less of the specified amount of salt when following cooking recipes

  • Everyone in the family should participate in the low-sodium diet so that the patient does not feel singled out

Dietary sodium needs to be controlled during any calcium testing, such as a calcium-loading test, to avoid affecting the results.


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