Posted by Tom Matthews

Immaterial wrote:
>
> > Salt does not cause high BP for many people, nor for many people with
> > high BP, will reducing salt lower it.
>
> I wish I could find the exact reference for this, but since it's printed on
> my office window and I'm at home, memory will have to serve.
>
> In support of Tom's comment above, seen as a medical heresy by many, JAMA
> published a study late last year which documents a direct connection
> between a reduced salt diet and increased mortality. In other words, those
> who eat more salt live longer. Anyone have the cite?

It probably concerns a recent analysis of NHANES. Here are a couple of
commenting abstracts:

Nutr Rev 1998 Oct;56(10):311-3
Dietary sodium intake and mortality.
Esslinger KA, Jones PJ
School of Dietetics and Human Nutrition, McGill University,
Ste-Anne-de-Bellevue, Quebec, Canada.

Results of a recent study of data from the National Health and Nutrition
Examination Survey (NHANES I) on sodium intake and all-cause and
cardiovascular mortality may call into question current recommendations
to limit salt intake. Further research is needed to explore the
relationship between sodium, cardiovascular disease, and mortality.

Wien Klin Wochenschr 1998 Jul 31;110(13-14):459-66
Salt and hypertension at the close of the millenium.
Luft FC
Franz Volhard Clinic, Max Delbruck Center for Molecular Medicine,
Medizinsche Fakultat der Charite, Humboldt University of Berlin, Federal
Republic of Germany. luft@fvk-berlin.de

"Can that which is unsavory be eaten without salt?" This question was
directed at none other than God by Job, who also had other important
problems to ponder. The question posed in this review is the notion that
essential hypertension is induced and/or sustained by an unnecessarily
high salt intake. If this is indeed the case, then a reduction of salt
intake might prevent or effectively treat essential hypertension. A
cross-sectional epidemiological study of salt intake in populations
showed a positive association of sodium excretion with median blood
pressure and the prevalence of hypertension; however, when four
disparate
populations were deleted, the associations disappeared. A Scottish
report on a similarly large population minimized the importance of
dietary sodium. A recently analysis of the National Health and Nutrition
Examination Survey (NHANES) data base does not support the idea that
lower salt intake improves all-cause or cardiovascular mortality;
however, the analysis is not without weaknesses. Salt-sensitivity is
based on the idea that some persons might be more susceptible to
salt-induced effects on blood pressure than others. Indeed, several
monogenic syndromes exhibit marked salt-sensitivity and their
clarification has facilitated our understanding of basic mechanisms.
Allelic variants of several genes may be important in salt-sensitive
patients with essential hypertension. Meta-analyses of intervention
trials in patients with essential hypertension show about a 5 mm Hg
decrease in blood pressure with salt restriction. Among the
normotensive, this decrease is less than 2 mm Hg. In terms of efficacy,
salt restriction has not been shown superior to weight loss or a
"vegetable" diet. Nonpharmacological approaches in hypertensive patients
should be based on a comprehensive approach.

And here appears to be the analysis itself:
(Note also the inverse association of mortality with calorie intake!)

Lancet 1998 Mar 14;351(9105):781-5
Dietary sodium intake and mortality: the National Health and Nutrition
Examination Survey.
Alderman MH, Cohen H, Madhavan S
Department of Epidemiology and Social Medicine, Albert Einstein College
of Medicine, Bronx, NY 10461, USA.
alderman@aecom.yu.edu

BACKGROUND: Population-wide restriction of dietary sodium has been
recommended. However, little evidence directly links sodium intake to
morbidity and mortality. The aim of this study was to assess the
relation of sodium intake to subsequent all-cause and
cardiovascular-disease (CVD) mortality in a general population. METHODS:
The first National Health and Nutrition Examination Survey established
baseline information during 1971-75 in a representative sample of 20729
US adults (aged 25-75). 11348 underwent medical examination and
nutritional examination based on 24 h recall. Two had no data on sodium
intake available. Vital status at June 30, 1992, was obtained for the
11346 participants through interview, tracing, and searches of the
national death index. Mortality was examined in sex-specific quartiles
of sodium intake, calorie intake, and
sodium/calorie ratio. Multiple regression analyses were done to assess
the relations with mortality. FINDINGS: There were 3923 deaths, of which
1970 were due to CVD. All-cause mortality (per 1000 person-years;
adjusted for age and sex) was inversely associated with sex-specific
quartiles of sodium intake (lowest to highest quartile 23.18 to 19.01,
p<0.0001) and total calorie intake (25.03 to 18.40, p<0.0001) and showed
a weak positive association with quartiles of sodium/calorie ratio
(20.27 to 21.71, p=0.14). The pattern for CVD mortality was similar
(sodium 11.80 to 9.60, p<0.0019; calories 12.80 to 8.94, p<0.0002;
sodium/calorie ratio 9.73 to 11.35, p=0.017). In Cox multiple regression
analysis, sodium intake was inversely associated with all-cause
(p=0.0069) and CVD mortality (p=0.086) and sodium/calorie ratio was
directly associated with all-cause (p=0.0004) and CVD mortality
(p=0.0056). By contrast, calorie intake in the presence of the two
measures of sodium intake was not independently associated with
mortality (all-cause p=0.86; CVD p=0.74). Analysis restricted to
participants with no history of CVD at baseline gave similar results.
INTERPRETATION: This observational study does not justify any particular
dietary recommendation. Specifically, these results do not support
current recommendations for routine reduction of sodium consumption, nor
do they justify advice to increase salt intake or to decrease its
concentration in the diet.

--Tom
Tom Matthews

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