QUOTE: ...In 1981, the FDA launched a series of "sodium initiatives" aimed at reducing the nation's salt intake.
Not until after these campaigns were well under way, however, did researchers set out to do studies that might be powerful enough to resolve the underlying controversy. The first was the Scottish Heart Health Study, launched in 1984 by epidemiologist Hugh Tunstall-Pedoe and colleagues at the Ninewells Hospital and Medical School in Dundee, Scotland. The researchers used questionnaires, physical exams, and 24-hour urine samples to establish the risk factors for cardiovascular disease in 7300 Scottish men. This was an order of magnitude larger than any intrapopulation study ever done with 24-hour urine samples. The BMJ published the results in 1988: Potassium, which is in fruits and vegetables, seemed to have a beneficial effect on blood pressure. Sodium had no effect.
With this result, the Scottish study vanished from the debate. Advocates of salt reduction argued that the negative result was no surprise because the study, despite its size, was still not large enough to overcome the measurement problems that beset all other intrapopulation studies. When the NHBPEP recommended universal salt reduction in its landmark 1993 report, it cited 327 different journal articles in support of its recommendations. The Scottish study was not among them. (In 1998, Tunstall-Pedoe and his collaborators published a 10-year follow-up: Sodium intake now showed no relationship to either coronary heart disease or death.)
The second collaboration was Intersalt, led by Stamler and Rose. Unlike the relentlessly negative Scottish Heart Health Study, Intersalt would become the most influential and controversial study in the salt debate. Intersalt was designed specifically to resolve the contradiction between ecologic and intrapopulation studies. It would compare blood pressure and salt consumption, as measured by 24-hour urine samples, from 52 communities around the globe, from the highest to the lowest extremes of salt intake. Two hundred individuals--half males, half females, 50 from each decade of life between 20 and 60--were chosen at random from each population. In effect, Intersalt would be 52 small but identical intrapopulation studies combined into a single huge ecologic study.
After years of work by nearly 150 researchers, the results appeared in the same 1988 BMJ issue that included the Scottish Heart Health Study. Intersalt had failed to confirm its primary hypothesis, which was the existence of a linear relationship between salt intake and blood pressure... UNQUOTE.
Source: "The (Political) Science of Salt."
By Gary Taubes, Copyright 1998 American Association for the Advancement of Science Science (August 14, 1998).
On the internet: http://www.junkscience.com/news3/taubes.htm |
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