10 Nov 2011 New study: blood pressure gains minimal from salt reduction
When it comes to salt, despite all the research and debate, there are no rights or wrongs. Yet. That’s the beauty of the salt debate: there’s so little reliable evidence that you can imagine just about any outcome. For all the talk about the growing menace of sodium in packaged foods, experts aren’t even sure that we’re eating more salt today than we used to. Now a review just published in the American Journal of Hypertension suggests the blood pressure gains of a reduced salt diet are minimal, at least for the general population – and the body seems to fight back against the changes.
Pooling data from 167 studies, the scientists concluded that the average reductions in blood pressure were:
- For whites with normal blood pressure: -1.27 points for systolic blood pressure (the higher, first number of a blood pressure reading) and -0.05 for diastolic pressure (the lower, second number).
- For whites with high blood pressure: -5.48 (systolic) and -2.75 (diastolic).
- The drops in blood pressure were higher for blacks and Asians, but the data were worse so the scientists are more tentative about the numbers.
- That’s from eating a diet with an average of 2,760 mg of sodium (not exactly low if you go by the government limits listed above) compared with an average of 3,450.
At the same time, the studies noted changes in certain molecules in the blood. All of the following went up:
- Renin (released by kidneys when blood pressure falls or blood salt levels fall low, to help constrict blood vessels and raise blood pressure again)
- Aldosterone (made by the adrenal glands when salt levels fall low, triggering more salt to be reabsorbed by the kidneys)
- Adrenaline (constricts blood vessels)
- Noraderenaline (ditto)
It’s almost as if the body is saying “salt / blood pressure levels falling – I’ll do what I can to ramp them up again.”
Blood cholesterol and triglyceride levels also rose.
The authors write: “Due to the relatively small effects and due to the antagonistic nature of the effects … these results do not support that sodium may have net beneficial effects in a population of Caucasians.” However, they did say that Caucasians with elevated blood pressure –as opposed to the population at large — could benefit from sodium reduction “as a supplementary treatment”.
They add that the benefit might be greater in blacks and Asians, but the data wasn’t firm enough to know that for sure.
Source: LA Times
Authors: Niels A. Graudal, Thorbjørn Hubeck-Graudal and Gesche Jürgens
Other reading: New scientific review questions the benefit of cutting down on salt