By reducing sodium consumption to less than 2 grams per day, the systolic (maximum) blood pressure could be reduced to 8 millimeters of mercury (mmHg) and the diastolic (minimum) blood pressure to 4. [1,2] This pressure reduction is similar to what could be achieved by losing 10 kg of weight or walking 30 minutes a day at a steady pace (see table). [3] Limiting sodium consumption is important not only for people suffering from hypertension, including those on antihypertensive drug therapy, but also for those with normal blood pressure. [1-3]

 

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In Italy, many thousands of the approximately 135,000 deaths [4], that occur every year from heart attacks or strokes, could be avoided: according to estimates based on clinical and epidemiological studies, [5] up to 26,000 deaths could be avoided, i.e. more than half of the deaths from lung cancer and more than 5 times the number of deaths due to road accidents every year (which in 2008 were less than 5000). [6]

 

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* The data refer to the reduction of systolic blood pressure (maximum). The diastolic blood pressure (minimum) drops by about half. 

 

Sodium and blood pressure: what clinical and epidemiological studies say

Several epidemiological studies and systematic reviews have shown that high salt consumption is associated with an increased risk of high blood pressure [7,8] and that taking less sodium may lead to a reduction in blood pressure. [1,2,8,9]

 

In general, the effects on blood pressure of a decrease in sodium intake are greater in hypertensive people but are also observed in non-hypertensive people. [1,2,8]

 

The largest randomized trial available is the DASH-sodium trial, conducted in the United States, which involved 412 people. [1] This study compared high and low sodium diets (3.5 compared to 1.2 grams per day) and showed that people taking less sodium had an average maximum (systolic) blood pressure reduction of 8 mmHg in hypertensive people and 6 mmHg in non-hypertensive people. The minimum blood pressure (diastolic) was reduced by 4 mmHg in hypertensive patients and 3 mmHg in non-hypertensive patients.

 

In a cross-sectional observational study the relationship between sodium urinary excretion and blood pressure was studied in more than 10,000 selected people in 52 communities in 32 countries [7]; in the 4 communities with low salt consumption (< 3 grams per day) no relationship between sodium and blood pressure was found, while in the remaining 48 communities (where sodium consumption varied between 6 and 12 grams per day) blood pressure was systematically higher the higher the sodium consumption. This relationship became more evident with age increasing. 

 

Sodium and risk of cardiovascular events: what clinical and epidemiological studies say

Taking less sodium could reduce the risk of cardiovascular disease, as several studies have shown. In particular, following information are reported:

• the systematic evaluation of available data from prospective studies lasting at least 3 years that have evaluated strokes and heart attacks in people with different levels of sodium intake. In particular, a meta-analysis was performed that summarized data from 13 studies for a total of nearly 180,000 patients. [5] According to this metanalysis, the intake of about 2 grams less sodium per day is associated with a reduction in strokes of about a quarter and a reduction in heart attacks of about a sixth. This means that in Italy [4] up to 12,000 heart attacks and up to 14,000 strokes could be avoided if we all halved the sodium intake by food. These data confirm the estimates made on the basis of previous metanalysis [10].
• two randomized trials, conducted on more than 3000 participants to evaluate the effectiveness of lifestyle interventions for the reduction of dietary sodium. Clinical results after 10 and 15 years show that out of 1000 people who received suggestions for a low sodium diet (1.8 grams per day), 15 avoided cardiovascular events (heart attack, stroke, interventions such as angioplasty and bypass). [11]

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1. Vollmer WM et al. Effects of Diet and Sodium Intake on Blood Pressure: Subgroup Analysis of the DASH-Sodium Trial. Ann Intern Med. 2001;135:1019-1028
2. He FJ, MacGregor GA. Effect of modest salt reduction on blood pressure: a meta-analysis of randomized trials. Implications for public health. Journal of Human Hypertension 2002;16:761–70
3. Chobanian AV et al. Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension 2003;42:1206-1252
4. ISTAT. Cause di morte in Italia, anno 2006. Disponibile su https://www4.istat.it/... (ultimo accesso: 28/1/2020 )
5. Strazzullo P, et al. Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studies. BMJ 2009;339:b4567 doi:10.1136/bmj.b4567
6. ISTAT. Incidenti stradali. Anno 2008 http://www.istat.it/... (ultimo accesso: 28/1/2020)
7. INTERSALT Cooperative Group. INTERSALT: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion. BMJ 1988;297:319-28
8. Jürgens G, Graudal NA. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride. Cochrane Database of Systematic Reviews 2004, Issue 1. Art. No.: CD004022. DOI: 10.1002/14651858.CD004022.pub2
9. Dickinson HO et al. Lifestyle interventions to reduce raised blood pressure: a systematic review of randomized controlled trials. Journal of Hypertension 2006, 24:215–233
10. He FJ, MacGregor GA. How Far Should Salt Intake Be Reduced? Hypertension 2003;42;1093-1099
11. Cook NR et al. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP). BMJ 2007;334:885-92