Diet and Health Implications for Reducing Chronic Disease Risk (1989) / Chapter Skim
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15 Electrolytes
15 Electrolytes
Pages 413-430
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From page 413... ...
iacta tion would be biologically useful. Thus, the physiology of mammals evolved to foster the conservation of salt by the kidneys, gastrointestinal tract, and sweat glands and to develop a taste for sodium chloride in the tongue and the salt appetite centers in the brain (Demon, 1982~.
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From page 414... ...
Acute depletion of salt resulting in heat exhaust tion and cardiovascular collapse may follow heavy sweating in people who have a high-salt intake and in whom adrenal mechanisms for conserving sodium have not been sufficiently activated (Cone, 1949~. Healthy Caucasian men, after adaptation tO heat and a moderately tow~sa~t intake for I week, maintain sodium balance on an intake of 90 mEq/day (S,200 mg of sodium chloride)
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From page 415... ...
Epidemiologic Evidence Methods for estimating salt intake have varied, and timed urine collections and dietary intake recalls frequently do not match.
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From page 416... ...
significantly associated with both systolic and dial stolic blood pressure after adjustment for age, sex, body mass index, and alcohol consumption. In cross-center analyses involving all 52 centers, median sodium excretion was positively and signif' icantly associated with median systolic blood pressure after adjustment for age, sex, body mass index, and alcohol consumption.
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From page 417... ...
Clinical Studies Several investigators have studied responses tO changes in sodium intake and sodium depletion in an attempt to identify people who are sensitive or resistant to the effects of salt on blood pressure. Salt loading acutely lowers forearm vascular resistance in healthy, normal people, but it increases resistance in those with borderline hypertension (Mark et al., 19751.
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From page 418... ...
Consequently, many efforts have been made to identify genetic markers in individuals likely to develop hypertension in response to excess sodium intake or other environmental variables, but these efforts have not been successful. In recent years, several ion transport systems have been described, and there have been attempts to identify abnormalities in such systems that might represent markers for genetic susceptibility to hypertension (Weissberg et al., 1983~.
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(1987) tested several different genetic models for their control of increased countertransport and found that results were most consistent with a major gene determining increased sodium-lithium countertransport activity superimposed on a background of polygenic control of blood pressure.
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Clinical trials of hypertension prevention using different levels of dierary salt in normotensive subjects over an extended period would provide additional evidence on the etiologic role of sodium chloride in hypertension. Gastric Cancer Studies in Humans Correa et al.
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From page 421... ...
Difficulties in obtaining valid estimates of salt intake have limited similar analyses in other countries. Some investigators have reported a positive correlation between gastric cancer mortality and stroke incidence and mortality, which they took as a surrogate measure of salt intake (Joossens, 1980; Joossens and Geboers, 1981; Tuomilehto er al., 1984)
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studied 101 black women about 20 years of age and found no significant correlation DIET AND HEALTH between blood pressure and sodium excretion. However, he found a modest positive correlation between the urinary sodium-potassium ratio and diastolic blood pressure.
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From page 423... ...
An intake of-3.5 gIday of elemental potassium is associated with a beneficial effect, and no threshold for this effect is known. Animal Studies DS rats fed a diet with 4% sodium chloride and 0.75% potassium developed hypertension, a gradual, progressive destruction of the kidney tubules, and an increase in the wall thickness of the renal arterioles.
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From page 424... ...
Experimental data indicate that a high salt intake can damage stomach mucosa and induce severe gastritis. These data combined with the consistent epidemiologic findings linking salted, dried, and pickled foods to increased gastric cancer risk suggest that salt can act as a cocarcinogen, perhaps by compromising the gastric mucosal barrier and facilitating initiation by a gastric carcinogen.
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1928. Use of sodium chloride, potassium chloride, sodium bromide, and potassium bromide in cases of arterial hypertension which are amenable to potassium chloride.
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1980. Effects of sodium chloride on gastric cancer induction by N-methylN'-nitro-N-nitrosoguanidine (MNNG)
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1978. The effect of high-sodium and low-sodium intakes on blood pressure and other related variables in human subjects with idiopathic hypertension.
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1975. Effects of high and low sodium intake on arterial pressure and forearm vascular resistance in borderline hypertension.
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1975. Effects in rats of sodium chloride on experimental gastric cancers induced by N-methyl-bJ'nitro-N-nitrosoguanidine or 4-nitroquinoline-1-oxide.
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1987. Dietary sodium intake and age in spontaneously hypertensive rats: effects on blood pressure and sympathetic activity.
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