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Salt and Blood Pressure: Is the Link Causal?

High salt intake is associated with high blood pressure across individuals and populations. Also, short-term experiments show that high salt loads lead to hypertension that is reversible. Neither of these two observation types provide “game, set and match”, however. The short-term effects might be different to any long-term effects. Further, the observational studies may be subject to a lurking confounding variable. However, if long standing hypertension could be reversed by a low salt diet, then this would be news in itself, as well as further evidence for the salt theory of hypertension. I therefore read the systematic review of randomised trials of reduction in dietary sodium by Huang and others in the BMJ with great interest.[1] They looked at no less than 133 randomised trials, including over 12,000 participants. The trials were all of high quality What do they show? Reducing salt intake lowers blood pressure; there is a dose response effect. The longer the trial, the larger the reduction in blood pressure. The higher the blood pressure at baseline, the greater the reduction observed. This is useful information for clinical practice and adds further evidence in favour of the salt hypothesis.

Richard Lilford, ARC WM Director


References:

  1. Huang L, Trieu K, Yoshimura S, et al. Effect of dose and duration of reduction in dietary sodium on blood pressure levels: systematic review and meta-analysis of randomised trials. BMJ. 2020; 368: m315.
Fri 24 Apr 2020, 11:00 | Tags: Blood pressure, Diet, Richard Lilford, Salt