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Study Needed on Salt's Health Risks
A new analysis says more research
is needed to demonstrate the toll a high sodium diet takes on
the body over a lifetime.
"A lifelong high-salt diet may
expedite the stiffening of the arteries," argues Dr. Geza Simon
of the Hypertension Clinic at the VA Medical Center in Minneapolis.
But to demonstrate the connection,
he says, scientists must conduct long-term experiments using physiologically
relevant amounts of salt.
"Only then will our public officials
be persuaded to pass legislation to reduce the salt content of
processed foods," Simon concludes in a report published in the
December issue of the American Journal of Hypertension.
Salt is a necessary component of
a healthy diet. People in developed countries consume four to
12 grams a day, Simon reports.
Salt increases average levels of
blood pressure, although some people have greater blood pressure
responses to salt than others, the National Heart, Lung, and Blood
Institute says.
Most Americans consume too much
salt, according to the institute. It says people should take in
less than 2.4 grams of sodium a day, or roughly 1 teaspoon of
table salt a day.
But studies to date have failed
to determine whether people are endangering their long-term health
by consuming too much salt.
That's partly because of the difficulty
of conducting such experiments. Industry is geared toward short-term
experiments that produce data in a year or two, Simon explains.
And researchers typically publish their data then move on to the
next grant application.
It is also "impractical and unethically
unjustifiable" to expose human subjects to high amounts of sodium
for a long time, he notes.
A simple solution would be to test
the life expectancy and cardiac function of laboratory rats exposed
to high sodium intake over a lifetime. Such an experiment would
take at least five years, from beginning to end, Simon says.
Richard Hanneman, president of
the nonprofit Salt Institute, an association of salt producers,
agrees that more study is needed. A landmark 1980s study of dietary
salt restriction and its effects on blood pressure, dubbed "Intersalt,"
only fueled debate as scientists interpreted the results differently,
he says.
"Proponents of salt restriction
just ignored the Intersalt study," he says.
Hanneman maintains that current
evidence does not support critics' claims that people are consuming
excessive and unhealthy levels of salt.
Simon's paper describes two ways
that salt load may have long-term consequences on cardiovascular
function and structure. One is a combined increase in cardiac
output and regional blood flow, which dilates arteries. The other
is an increase in plasma sodium concentration, which may impact
vascular health.
Hanneman agrees that high salt
diets have been shown to promote the dilation of blood vessels,
but he doesn't see that as a health risk. "It's vessel constriction
that's unhealthy." That's why people with high blood pressure
take drugs like ACE inhibitors and calcium channel blockers, he
says.
More information
To learn more about salt and its
health effects, visit the National
Heart, Lung, and Blood Institute and the Henry
Ford Health System.
Reference
Source 101
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