July 6, 2011 -- Reducing salt intake in the diet produces a small decline in blood pressure, according to a new review of research. But the evidence is not conclusive on whether salt reduction has an effect on getting cardiovascular disease or dying from it, the researchers say.
The findings are not a call to eat salt with abandon, warns researcher Rod Taylor, PhD, MSc, professor of health services research at the University of Exeter in the U.K.
The review evaluated nearly 6,500 people and is published online in the American Journal of Hypertension and the Cochrane Database ofSystematic Reviews 2011.
Taylor suspects he found no strong evidence that salt reduction lowered heart disease risk and death because the numbers studied were too small. And those studied may have lowered salt intake at first but then slid back into old habits, he says.
In the short term, up to two years after study participants were advised to reduce salt, he found a trend of reduced deaths, Taylor tells WebMD. "In the longer term, out about 10 years, that benefit disappeared. And we believe that is because people were not able to maintain that behavior."
"What this says is, giving people advice to reduce their dietary salt is not enough on its own," Taylor says.
What is needed is a multi-pronged approach, he says, including better labeling, at least in the U.K., and government help, along with more research studies looking at the link.
However, the Salt Institute sees the new findings differently. In a statement, the industry group said the new findings are reason for the government to end efforts to reduce salt intake until a benefit can be proven.
Taylor's team looked at seven published studies that included nearly 6,500 participants. Some participants had normal blood pressure and some had high blood pressure. One study looked at salt restriction in people with heart failure.
Reducing salt was linked with a mild reduction in blood pressure. Systolic blood pressure decreased slightly, by about 1 to 4 points. Systolic pressure is a measure of pressure while the heart is beating. It is the top number of the reading.
However, the researchers found that salt restriction increased the risk of death from all causes in those with heart failure.
They concluded there was not enough evidence to say whether the reduced salt had an effect on cardiovascular deaths in the other participants.
A large-scale clinical trial looking at the impact of dietary salt reduction on health outcomes is needed, according to the Salt Institute.
In the statement, Mort Satin of the Salt Institute says health policy on salt set by the government needs to be based on evidence. "The public health agencies have deliberately ignored the preponderance of clinical evidence in order to pursue a reckless salt reduction agenda based far more on ideology than science," according to Satin.