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Why new salt study is flawed

A University of Warwick academic and WHO adviser says that a study which claim salt may not be as damaging to health as is usually claimed is flawed.

“The latest publication in The Lancet from the PURE study does not add anything to the knowledge of the effects of salt on cardiovascular outcomes and, more importantly, does not provide any evidence that reducing population sodium consumption by a moderate amount causes harm.

“The PURE study, due to the numerous flaws highlighted in the last few years in international journals, is not fit to address any of the issues regarding salt consumption and cardiovascular outcomes.

“The assessment of exposure by spot urine collections and the use of the Kawasaki formula is flawed, leading to biased estimates, also shown in the PURE validation of Chinese data. The Kawasaki formula leads to a systematic bias – this bias leads to an overestimate of CVD risk at lower levels of intake. The effect of this bias ‘creates’ a J-shaped curve between sodium consumption and cardiovascular outcomes, as recently shown using data from the Trials Of Hypertension Prevention (TOHP) I and II (published in International Journal of Epidemiology a few weeks ago) – the TOHP trials data was not taken into consideration in the present study. Several repeated 24h urine collections with sodium estimates do show a linear and graded relationship between sodium consumption and CVD risk, with no J shape at all.

“The use of ‘ecological’ associations, which relate average exposures with average outcomes, is immaterial to the interpretations offered by the authors and editorial, due to the lack of allowance for important confounders.

“Concerted actions globally, led by the World Health Organization and endorsed by multiple international health organizations should continue to reduce population salt consumption.”

Prof Francesco Cappuccio, Chair of Cardiovascular Medicine and Epidemiology, Warwick Medical School

For more information contact Nicola Jones, Media Relations Manager, University of Warwick or 07920531221