Evidence Summary
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Key messages from scientific research that's ready to be acted on
Got It, Hide thisReduced salt intake reduces blood pressure in people with or without hypertension
He F, Jiafu L, MacGregor G. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ. 2013;346:1325.
Review question
What is the effect of long-term salt reduction on blood pressure?
Background
Salt raises blood pressure (BP) in some people. A lower salt intake is related to a reduced risk of heart attacks and stroke.
Healthy adults need only 1,500 mg of salt per day. The maximum recommended daily intake is 2,300 mg. 1 teaspoon of salt = 2,400 mg sodium.
For most people, about 85% of salt intake is from food, with only about 15% added by salt shaker.
How the review was done
This summary is based on a systematic review of 34 randomized controlled trials of 3230 people 22 to 73 years of age. Publication period was 1973 to 2009.
- 12 trials included 2,240 people with normal BP (median BP 127/77 mg Hg). Their salt intake ranged from 7,500 to 11,700 mg/day. Study duration ranged from 1 month to about 1 year.
- 22 trials included 990 people with high BP (median BP 148/93 mm Hg). Their salt intake ranged from 7,300 to 11,200/day. Study duration ranged from about 1 month to about 3 years.
Reduced salt intake for 4 or more weeks was compared with usual salt intake.
The main outcomes were systolic and diastolic BP.
What the researchers found
For all people (high or normal BP)
- The average reduction in salt intake was 4,400 mg/day.
- For systolic BP, this reduction resulted in an average lowering of 4.18 mm Hg.
- For diastolic BP, the average lowering was 2.06 mm Hg.
- A daily reduction of salt intake of 6,000 mg was associated with a lowering of systolic BP of 5.8 mm Hg.
For people with high BP
- The average reduction in salt intake of 4,400 mg/day resulted in an average lowering of 5.39 mm Hg. for systolic BP.
- The average lowering of diastolic BP was 2.82 mm Hg.
For people with normal BP
- The average reduction in salt intake of 4,400 mg/day resulted in an average lowering of 2.42 mm Hg for systolic BP.
- The average lowering of systolic BP was 1.00 mm Hg.
Conclusion
A reduction in salt intake for 4 or more weeks reduces blood pressure in patients with or without hypertension, regardless of sex or ethnicity.
Related Topics
Glossary
The lower number in a blood pressure reading. It is the pressure when the heart rests between beats.
The number separating the higher half from the lower half. 50% are above that point and 50% are below.
Studies where people are assigned to one of the treatments purely by chance.
A comprehensive evaluation of the available research evidence on a particular topic.
The higher number in a blood pressure reading. It is the pressure in the arteries when the heart beats.
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