Salt: flawed research should not divert actions to reduce intake

11th July 2016

Following a study that was published in the Lancet in May by Mente et al., which suggested that salt reduction need only be confined to individuals with hypertension who have a high salt intake (rather than the population as a whole), CASH has published a commentary highlighting the flaws with the methodology of this paper and arguing the case for population-wide salt reduction. The commentary highlights two main issues with the study:

  • The use of a single spot urine to measure individual salt intake, which is not an accurate or reliable measure due to the large day-to-day variations in salt intake, thus making it highly subject to error;
  • Reverse causality – a large proportion of the study participants were taking part in treatment trials for people with CVD or at high risk of CVD (i.e. an ill population) who are therefore likely to eat less food and consume less salt (or make a conscious effort to reduce their salt intake) and so it is not the low salt intake causing their death, but rather the illness causing their low salt intake.

The commentary highlights that evidence from other well-designed cohort studies that have taken multiple measurements of 24-hour urinary sodium (the gold standard for measuring salt intake in the population), large-scale salt reduction trials and public health interventions have routinely showed that a lower salt intake is associated with a reduced risk of CVD. Several countries that have implemented salt reduction initiatives, including the UK, have seen a fall in salt intakes and subsequent fall in blood pressure and mortality from CVD as well as huge savings to health care costs. The commentary argues that the evidence for population-wide salt reduction and its health benefits is unequivocal, and that studies like the one by Mente et al. should not deter progress in reducing population salt intake and reaching the WHO target of less than 5g per day.

To read the full commentary please visit Nature Reviews Nephrology.