Using less amount of salt in diet can lead to slight reduction in blood pressure in the medium term, a new study has claimed.
However, whether in the long term this can also reduce the risk of late complications in people with sustained high blood pressure, otherwise known as essential hypertension, and whether in the long term their anti-hypertensive medication can be reduced remains unresolved, the study by the Institute for Quality and Efficiency in Health Care (IQWiG) concluded.
The study has been published in the form of a rapid report on 20 July 2009. This rapid report is part of a package commissioned by the Federal Joint Committee (G-BA), in which the benefit of various non-drug treatment strategies for high blood pressure are to be assessed. Stress management and more physical activity are also included, as well as giving up smoking and cutting down alcohol consumption.
This rapid report was prepared on the basis of secondary literature. In principle, this can be done if current, high quality systematic reviews are already available on a given topic. This was the case with reducing salt intake in hypertension, as IQWiG's preliminary search revealed.
To reach the conclusion, IQWiG searched for systematic reviews that compared the following patients with hypertension: an intervention group, which was to follow a low-salt diet over a long period, versus a control group, which either did not have this target or whose salt reduction was not so great as in the intervention group.
The minimum duration of the studies had to be 4 weeks. In order not to overlook any current and potentially relevant studies, IQWiG also conducted an update search of recently published primary studies.
IQWiG was able to include in its assessment 7 reviews, in which the results of between 520 and 3391 participants from a total of 62 randomized controlled trials were analysed together.
IQWiG found that no conclusions on late complications could be drawn from the available data. The reason for this is that none of the studies had the primary goal of investigating the effects of a low-salt diet on cardiovascular disease or all-cause mortality.
However, the investigations consistently show that a reduction in salt intake can assist in lowering blood pressure: over a period of up to one year, there was a mean drop of 3.6 to 8 mmHg in systolic values and a mean drop of approximately 2 to 3 mmHg in diastolic values. This applied primarily to patients who did not take any additional anti-hypertensive drugs.
The sustainability of this effect, however, remains unclear.