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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 BMJ report.
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.
The research, based at Harvard Medical School in Boston, USA, provides some of the strongest evidence to date that lowering the amount of salt in the diet reduces the long-term risk of future cardiovascular disease, say the report’s authors.
The researchers followed up participants from two trials from the 1990s, conducted to analyse the effect on blood pressure of reducing dietary salt.
All participants had high to normal blood pressure (pre-hypertension), so were at relatively greater risk of developing cardiovascular disease. A total of 744 people took part in the first Trial of Hypertension Prevention, completed in 1990, and 2,382 in the second, completed in 1995. In both trials participants reduced their sodium intake by 25–35% alongside a control group who did not cut back on salt intake.
Detailed information about cardiovascular and other health problems was sought from participants in the earlier trials. As part of this, the 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. The researchers obtained information from a total of 2,415 of the participants (77.3%), 200 of whom had reported some sort of cardiovascular problem.
The reduction in the risk of developing cardiovascular problems as a result of sodium reduction intervention was substantial. 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.
Cook, N. Long-term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP).
BMJ Online First 18/4/07
