Salt blunts effects of blood pressure drugs: Study

10-Sep-2009 - Last updated on 11-Sep-2009 at 10:49 GMT

Continued high dietary intakes of salt may make people resistant to blood pressure-lowering drugs, says a new study that provides “additional support of efforts to reduce salt content in foods”.

Up to 30 per cent of people with high blood pressure (hypertension) fail to respond to anti-hypertensive medications, a condition known as resistant hypertension. Consuming a diet high in salt, despite medication, may contribute to this condition, according to findings published in Hypertension.

“This is the first study to assess the effects of low dietary salt ingestion in subjects with resistant hypertension,” wrote the researchers, led by Eduardo Pimenta from the Hypertensive Unit at the Princess Alexandra Hospital in Brisbane, Australia.

Despite reductions being made in the salt content of foods, the research adds to calls for more progress to be made by food manufacturers.

Salt is of course a vital nutrient and is necessary for the body to function, but campaigners for salt reduction, like the Consensus Action on Salt and Health (CASH) consider the average daily salt consumption in the western world, between 10 and 12g, far too high. WHO/FAO recommends a daily intake of 5 grams per day to control blood pressure levels and reduce hypertension prevalence and related health risks in populations.

Worryingly, despite the subjects reportedly adhering to a low-salt diet, blood measures of sodium indicated that they consumed an average of 11.6 grams of salt every day.

“These findings indicate that in spite of reporting a salt-restricted diet, these patients were continuing to ingest a diet very high in salt content,” wrote Pimenta and his co-workers.

“Taking into consideration that 75 per cent of the daily intake of sodium in Westernized countries is from salt added during commercial processing of foods or during food preparation by restaurants, reductions in the sodium content in the food supply would be a critical component to achieve lower levels of sodium intake,” they added.

Study details

Pimenta and his co-workers recruited 12 people with resistant hypertension and randomly assigned them to receive either a low (about 3 grams of salt per day) or high sodium diets (about 15 g of salt per day) for seven days. This was followed by a two week washout period, and the participants were then crossed over to the other group.

All of the participants were taking an average of 3.4 anti-hypertensive medications, and had an average blood pressure of 145.8/83.9 mmHg. The low salt diet was associated with a 22.7 and 9.1 mmHg decreased in systolic and diastolic blood pressure, respectively, compared to the high-salt diet, despite the continued taking of the medication.

“These data demonstrate that patients with resistant hypertension benefit from intensive dietary salt restriction and provide rational for inclusion of specific recommendations in dietary guidelines regarding salt intake for the treatment of resistant hypertension,” wrote the researchers.

“The current findings also provide additional support of efforts to reduce salt content in foods,” they concluded.

Source: Hypertension
Volume 54, Pages 475-481, doi:10.1161/HYPERTENSIONAHA.109.131235
“Effects of Dietary Sodium Reduction on Blood Pressure in Subjects With Resistant Hypertension: Results From a Randomized Trial”
Authors: E. Pimenta, K.K. Gaddam, S. Oparil, I. Aban, S. Husain, L.J. Dell'Italia, D.A. Calhoun