November 9, 2011

expert reaction to new research on sodium and health, as published in the American Journal of Hypertension

Research compared various health impacts of low-salt vs high-salt diets.

Prof Francesco Cappuccio, Head of the WHO Collaborating Centre for Nutrition and Cephalon Professor of Cardiovascular Medicine & Epidemiology, University of Warwick, said:

“This study is the third update of previous work. In 2008 the Cochrane Review site published their second update with a significant criticism attached (p. 113-6). The criticisms are not addressed in this update and remain as follows:
1.,There is nothing really new in the study. Ideas are repackaged and estimates are updated.
2.,Most studies included are of very short duration (less than 4 weeks) – in normotensives median duration 7 days, in hypertensives 28 days
3. Most studies test very extreme changes in salt intake (para-physiological) – mean difference in sodium intake of 150 mmol in normotensives and 125 in hypertensives (more than double any national recommendation).
4.,Changes in renin and aldosterone are physiological responses to changes in salt intake and there is no evidence of any long term harm – thiazide diuretics lower BP, induce a very large increases in renin and aldosterone and reduce stroke rates and CHD very effectively.
5.,Changes in lipids are detected in acute (mainly due to haemoconcentration following rapid changes in volume status) but they are not seen in the medium term (after 4 weeks).
6.,Despite the large number, the authors do not find significant changes in LDL-cholesterol, the only predictor of risk amongst all their measures.
7.,Their study has no bearing with population approach of moderate salt restriction.
8.,The cohort studies cited all have methodologic issues related to estimation of sodium intake, well discussed in recent scientific literature, not quoted by the authors. There are misquotes in places and omissions of other substantial evidence contradicting their discussion points.
9.,The present study should not distract our attention for implementing salt reduction policies at population level globally, as directed by national governments, the World Health Organization and the United Nations.”

‘Effects of Low-Sodium Diet vs. High-Sodium Diet on Blood Pressure, Renin, Aldosterone, Catecholamines,Cholesterol, and Triglyceride (Cochrane Review)’, Graudal et al, published in the American Journal of Hypertension on Weds 9 Nov.