The Great Salt Hoax Part I
The Institute of Medicine (IOM) is back in the news with the sodium chloride-can-be-dangerous-for-your-health game. The IOM describes itself as "independent, nonprofit organization that works outside of government..." But wait, the organization, is indeed the health arm of the internationally esteemed National Academy of Sciences. One could not find a more prestigious Institute, run by the country's top physicians and scientists. Yet, this begs the question of accepting as holy write the pronouncements of any organization wearing the costume of officialdom in health matters.
Recent History of the Anti Salt Crusade
Almost 50 years ago in the 1960's Lewis Dahl developed a strain of salt sensitive rats that routinely developed hypertension to support his firm belief in the value of salt restriction to prevent high blood pressure. When he analyzed different populations. Dahl also claimed to demonstrate a linear relationship between salt intake and blood pressure. As Dr. Paul Rosch has pointed out in two previous newsletters five years ago (here and here), this was widely cited by other low salt proponents as proof of the role of salt in causing hypertension. What they often neglected to mention is that Dahl's rats would have to be fed an amount of salt equivalent to over 500 grams daily for an adult human.
This and other previous work prompted recommendations on dietary sodium reduction in the 1969 White House Conference on Food, Nutrition and Health and led to the 1979 Surgeon General's Report condemning salt as a clear cause of high blood pressure. Since then, the government has spent untold millions in an unending crusade to justify claims linking dietary sodium and hypertension-and therefore heart attacks and strokes.. This started with the $1.3 million INTERSALT study of 10,000 subjects in 52 centers around the world. As anticipated, researchers reported that societies (and individuals) with higher sodium intakes also had higher average blood pressures, seemingly clinching the government's ľand Dahl's-case.
However, as Dr. Rosch observes, when the four primitive societies with both extremely low sodium intake and very low blood pressures were excluded no such correlation was found in the other 48 groups. "The INTERSALT researchers conveniently neglected to mention that the population of these four countries also had less stress, less obesity, ate far less processed foods and lots of fruits and vegetables. They also tended to die at younger ages from other causes and often too soon to have developed any significant degree of coronary disease. When the available data from the other more civilized societies was reviewed, statisticians found that as sodium intake increased there was a decrease in blood pressure, just the opposite of what had been reported." When confronted with these discrepancies, the researchers re-analyzed their data in an attempt to justify their conclusions, thus mining or "massaging" the data, an all too prevalent kind of statistical shenanigan, including "cherry picking" data, all of which poisons much of the medical literature. In this case, the re-analyzed findings suggesting only that higher dietary sodium could be correlated with a faster rise of blood pressure as people grew older.
Is Salt Killing Us?
This observation failed to address the major purpose of determining whether increased dietary sodium was related to higher rates of illness or death for everyone. Yet in a new report, the IOM declares that reducing sodium consumption to 2400 mg. could reduce deaths by 100,000 annually, saving the country $73.4 billion. Other observes writing in the Annals of Internal Medicine say that a voluntary effort by the U.S. food service industry to reduce salt in processed foods 9.4% could have far-reaching implications for the health of Americans, preventing strokes and heart attacks in nearly a million Americans and saving $32.1 billion in medical costs. (Note the studied precision of these imaginary numbers.)
In an editorial in the Journal of the American Medical Association, Reducing Dietary Sodium: The Case for Caution', JAMA, June 9, 2010, Jane E. Henry, chair of the IOM Committee on Strategies to Reduce Sodium Intake admits "We were not asked to go back and review the research on sodium reduction and its effects; we took the evidence as a given..." I suspect but cannot prove that they started, if not ended with the INTERSALT study.
Voices of Disagreement
Among many critics is Professor Michael H. Alderman from the Department of Epidemiology and Population Health at Albert Einstein College of Medicine who asks if the available research justifies a population-wide restriction on sodium in food. He points out that no clinical trials actually link sodium intake to increased mortality in people who are otherwise healthy. All the trials conducted so far involved only heart failure patients Moreover, in the case of sodium consumption at least 13 studies have been conducted with conflicting results. "Without any data on how sodium reduction would affect the general population, these clinical trials have zero relevance to public health policy." We are, of course, dealing with different populations, different diets, varying sodium intakes, and, therefore multiple mathematical biases. "Neither more observational studies nor further debate over the available studies is likely to resolve this public health controversy," writes Alderman.
George Bakris, MD, president of the American Society of Hypertension, and a professor of medicine at the University of Chicago reminds us that the real issue is the inherent limitations of observational studies. That requires a randomized clinical trial, which Bakris does not see happening. "You would need 100,000 people followed over 20 years to get a definitive answer. The reality is that there will never be such a study."
A previous Postscript: The German poet Otto Hartleben was feeling quite ill and consulted a physician who, after a thorough examination, prescribed complete abstention from smoking and drinking. Hartleben picked up his hat and coat and started for the door. The doctor called after him, "My advice, Herr Hartleben, will cost you three marks." "But I'm not taking it," retorted Hartleben, and vanished.
Martin F. Sturman, MD, FACP
Copyright 2010, Mathemedics, Inc.
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