People who significantly cut back on the amount of salt in their diet could reduce their chances of developing cardiovascular disease by a quarter, according to a report on bmj today.

Researchers in Boston also found a reduction in salt intake could lower the risk of death from cardiovascular disease by up to a fifth.

Cardiovascular disease refers to the group of diseases linked to the heart or arteries, for example a stroke or heart disease. While there is already a substantial body of evidence showing that cutting back on salt lowers blood pressure, studies showing subsequent levels of cardiovascular disease in the population have been limited and inconclusive.

This research provides some of the strongest objective evidence to date that lowering the amount of salt in the diet reduces the long term risk of future cardiovascular disease, say the authors of the report.

Researchers followed up participants from two trials completed in the nineties which had been conducted to analyse the effect that reducing salt in the diet had on blood pressure.

All the participants had high-normal blood pressure (pre-hypertension). They were therefore at greater risk of developing cardiovascular disease. 744 people took part in the first Trial of Hypertension Prevention which was completed in 1990, 2382 in the second, which ended in 1995. In both trials participants reduced their sodium intake by approximately 25% - 35% alongside a control group who didn't cut back on their salt intake.

Detailed information about cardiovascular and other health problems was sought from participants in the earlier trials. As part of this researchers found that participants who had cut back on salt during the trials tended to stick to a lower salt diet compared to those who had been in the control group. In total the researchers obtained information from 2415 (77.3%) participants, 200 of whom had reported some sort of cardiovascular problem.

The reduction in the risk of developing cardiovascular problems as a result of the sodium reduction intervention was substantial. The results showed these pre-hypertensive individuals were 25% less likely to develop cardiovascular problems over the course of the 10-15 years post-trial. There was also a 20% lower mortality rate. This risk reduction was evident in each trial.

To the authors knowledge this study is the first and only study of sufficient size and duration to assess the effects of a low salt diet on cardiovascular problems based on randomised trial data. It provides unique evidence that lowering salt in the diet might prevent cardiovascular disease.

"Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP)
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