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“font-size: 10.0pt; font-family: Verdana; mso-font-kerning: 0pt; font-weight: normal; mso-bidi-font-weight: bold;”> I am obviously quite passionate about articles related to hypertension control. I recently read the full study in the Journal of the American Medical Society (JAMA) [titled “Fatal and Nonfatal Outcomes, Incidence of Hypertension, and Blood Pressure Changes in Relation to Urinary Sodium Excretion,” published May 4, 2011 “font-size: 10.0pt; font-family: Verdana; font-weight: normal; mso-bidi-font-weight: bold;”>] and was appalled that such a scientifically flawed study could get published in such a reputable journal. The limitations of the study are jaw-dropping: “font-family: Verdana; font-size: 13px;”>
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“font-size: 10.0pt; font-family: Verdana;”>The sample size in the
study was insufficient to detect a significant change in the
outcome (death due to cardiovascular disease) over the relatively
short study period. That is to say, the study
was underpowered.
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“font-size: 10.0pt; font-family: Verdana;”>The 24 hour urinary
collections were unreliable. In several occasions the urine
collections were not collected properly, leading to an inadequate
collection. That would underestimate the amount of sodium
excretion.
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“font-size: 10.0pt; font-family: Verdana;”>The study was an
observational one, meaning the investigators took a broad snapshot
of sodium intake in one period of time. The best approach would be
to conduct a randomized clinical trial, assigning patients to
either a low-sodium, normal sodium, or high sodium diet and
following then prospectively for several years, maybe more than a
decade. Such a study would obviously be quite expensive, and
perhaps unethical given what we know about the adverse effects of
high sodium diets.
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“font-size: 10.0pt; font-family: Verdana;”>The results of the study
are inconsistent with the large body of evidence gained over the
past 25 years.
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“font-size: 10.0pt; font-family: Verdana;”>The authors are unable
to provide a credible hypothesis linking low sodium intake to the
causal pathway leading to increased cardiovascular
disease.
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“font-size: 10.0pt; font-family: Verdana;”>The study participants
were relatively young (mean age 49) and mostly healthy.
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“font-size: 10.0pt; font-family: Verdana;”>The participants were
European – thus we cannot generalize the results to other ethnic
groups, or to other geographic regions for that
matter.
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“font-size: 10.0pt; font-family: Verdana;”>The current FDA guidelines, which I strongly support, call for a maximum of 2,300 milligrams of sodium a day (the amount found in a teaspoon of salt), and 1,500 milligrams of sodium (two-thirds of a teaspoon) for people who have high blood pressure or are at high risk of developing it. The latter group includes people who are over the age of 40, are African American, or have somewhat elevated blood pressure (prehypertension)—a group that includes almost 70 percent of adults in the United States. Those recommendations, embraced by the 2010 Institute of Medicine (IOM) report, are based on the known association between high sodium diets and high blood pressure. According to the IOM report and the Centers for Disease Control, hypertension increases the risk for heart disease, stroke, congestive heart failure and renal disease. Heart disease is the largest cause of death in the United States, accounting for more than one-quarter of deaths in 2006, and stroke is the third-largest underlying cause of death, at 5.7 percent. Overall, excessive sodium intake accounts for $73.4 billion a year in direct and indirect costs. Health disparities in rates of hypertension are also well known: according to the National Health and Nutritional Examination Study African Americans have a 30% higher prevalence of hypertension compared to Whites. As a kidney specialist I see far too many young people, mostly African Americans, presenting with advanced kidney failure secondary to hypertension, a treatable disorder. “font-family: Verdana; font-size: 13px;”>
“font-size: 10.0pt; font-family: Verdana;”>The Salt Institute is jumping for joy at the results of the JAMA study. They are all too eager to have the FDA rollback its recent guidelines on sodium restriction. As we know, it can take years to modify the behaviors and lifestyles associated with high salt intake, however all the effective preventive health messages can be jeopardized by one well-intentioned but poorly-designed study. We must aggressively counter-act the confusing message outlined in the JAMA study while opening up the channels for even more intense community education.
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