JAMA 2011;306:2229-38 [Free full-text JAMA article PDF] [PubMed® abstract]
[EXCERPTS
Encouragement to eat less salt has been a common feature of public
health advice in recent years, although guidelines disagree about the
intake we should be aiming for. Many observers believe the lower the
better, although a recent analysis identified a J shaped association
between sodium excretion (as a proxy for intake) and cardiovascular
events in high risk adults.
Those excreting 4-6 g of sodium a day had the lowest risk of
cardiovascular events, including death from cardiovascular disease
(15.2% (2148/14 156)). Risk was significantly higher in those who
excreted more (>8 g: 24.1% (204/847); fully adjusted hazard ratio
1.49, 95% CI 1.28 to 1.75) or less (<2 g: 1.21, 1.03 to 1.43; 2-3 g:
1.16, 1.04 to 1.28) than this reference amount. Should agencies that
recommend no more than 1.5 g a day rethink their advice?
Not yet, says a linked editorial (p 2262). We have good evidence
from randomised trials that eating less salt protects cardiovascular
health. There is always room for more trials, to fine tune the safe
range, but the principle is established and shouldn’t be overturned by
observational work, however powerful and sophisticated it is. The J
shape looks convincing, but adults on the “upstick” at the lower end of
the curve may be avoiding salt because they are already ill. Isolating
the effects of salt from other dietary habits is another challenge for
observational studies, says the editorial, and estimating sodium
excretion from one early morning urine sample was a particular challenge
for this one. Policy makers should stand firm for now.
Cite this as: BMJ 2011;343:d7549
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