|
|
|
CHLORIDE
Chloride is an anion (a negatively charged ion), generally consumed as
sodium chloride (NaCl) or table salt. There is a high correlation between the
sodium and chloride contents of the diet, and only under unusual circumstances
do levels of sodium and chloride vary in the diet independently. Adequate intake
of sodium chloride is required for maintenance of extracellular fluid volume.
Chloride is both actively and passively absorbed. Urine excretion reflects
chloride intake, with low or no chloride found in deficiency states.
In general chloride has received little attention in dietary assessment and
has been omitted from food composition tables. However, chloride content of
infant cow's milk and soy formulae has stimulated interest in the past 15 years
because of iatrogenic hypochloremia induced by several infant formulas with
deficient chloride concentrations.
Deficiencies:An adequate intake of sodium chloride to
sustain losses may result in hypotension (abnormally low arterial blood
pressure). Depending on intake of "free" water, hyponatremia (deficiency of
sodium in the blood) and hypochloremia may ensue, such as in water overload,
wasting, and trauma with sequestration of extracellular fluid as in burns.
Selective chloride deficiency (without sodium deficiency) may result from
vomiting, as in pyloric stenosis in infancy or continuous gastric suction with
resulting metabolic alkalosis. A familial autosomal recessive condition with
chronic diarrhea and defective chloride reabsorption (Barter's Syndrome) also
causes hypochloremia. Renal tubular disorders, cystic fibrosis with excessive
sweating and loss of chloride in the perspiration and diuretic use may also
cause low chloride states. As mentioned above, inadvertent feeding of chloride
deficient infant formulae (<5 mEq Cl/L) resulted in 141 infants in the first
year of life developing failure-to-thrive, anorexia, weakness and some ambiguous
findings of slow development. Deficiency of chloride alone leads to contraction
of extracellular fluid volume and metabolic alkalosis which, in turn, leads to a
deficiency of potassium by increasing urinary excretion of potassium.
Diet recommendations: High sodium, low chloride diets should
be avoided. In the absence of sodium chloride losing disorders (e.g., excessive
sweating, cystic fibrosis, Addison's disease) several health agencies have
recommended that the general population not consume more than 6 g NaCl/day. This
recommendation may be of benefit in decreasing cardiovascular morbidity and
mortality associated with higher levels of blood pressure in the resting stat.
The minimal daily requirement for sodium chloride for normal individuals is less
than 2 g NaCl/day. For chloride alone, the Estimated Minimum Requirements per
day set by the Food and Nutrition Board are as follows: infants: 0-6 months, 180
mg; 6 months-11 months, 300 mg; 1 year, 350 mg; 2-5 years, 500 mg; 6-9 years,
600 mg; and adolescents and adults, 750 mg.
Food sources: With few exceptions (e.g., monosodium
glutamate and sodium bicarbonate) sodium and chloride are most often consumed as
sodium chloride (salt). Human milk contains about 420 mg/L and infant formula is
now required to contain 55-65 mg/100 kcal and is not to exceed 150 mg/100 Kcal.
Undiluted cow's milk contains about 900-1020 mg/L. Infant formula contains
10.6-13.5 mEq/L and formula for older infants (follow-up formula), 14-19.2 mEq/L.
Recommended intakes are 2-4 mEq/L/Kg for infants and children and 60-150 mEq
(total) adolescents.
Recent research: The potential of sodium chloride to
increase blood pressure is dependent on concomitant high dietary intake of both
sodium and chloride. Blood pressure is not increased by selective sodium
(without chloride) loading. |
|
