A report by the German Institute for Quality and Efficiency in Health Care (IQWiG) concludes that adults who use less salt in their diet can experience a slight reduction in their blood pressure in the medium term. 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.

This report is part of a package in which the benefit of various non-drug treatment strategies for high blood pressure is to be assessed. Stress management and more physical activity are also included, as well as giving up smoking and cutting down alcohol consumption. IQWiG has already completed a report on the effect of weight reduction on blood pressure.

The report was prepared on the basis of secondary literature. 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 analyzed 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. Moreover, most of the studies were only of a few months' duration and had low numbers of participants, which meant that possible differences in late complications might not have been detected with certainty.

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.

Blood pressure is measured in millimeters of mercury (mm Hg), and expressed with two numbers, for example, 120/80 mm Hg. The first number (systolic pressure) is the pressure when the heart beats while pumping blood. The second number (diastolic pressure) is the pressure in large arteries when the heart is at rest between beats.

High blood pressure is defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg.

The sustainability of this effect, however, remains unclear. The authors of at least one review report that the observed advantage disappears when the analysis is restricted to studies of a longer duration (at least 6 months).

None of the reviews solely considered patients who were simultaneously taking anti-hypertensive drugs or separately analysed data for participants on concomitant medication. The additional blood pressure-lowering effect of a low-salt diet in these patients is therefore uncertain.

Basically, it is still not known whether people with essential hypertension can reduce their drug dosage through less salt intake.
References:
1. Institute for Quality and Efficiency in Health Care.