For decades, scientists have suspected that excessive salt intake may cause elevated blood pressure, which is a risk factor for heart disease.
However, studies have provided mixed results, partly because people’s blood pressure responds to salt intake in different ways. Those who are prone to hypertension when eating too much salt are referred to as being salt sensitive.
Recently, the American Heart Association published a comprehensive review of the available evidence on salt sensitivity. Here is a summary of the review’s main points.
This was a review of the available evidence regarding salt sensitivity.
What Is Salt Sensitivity?
Salt sensitivity is a measure of how blood pressure responds to changes in dietary salt intake.
The way people’s blood pressure responds to salt intake differs. As a result, not everyone is salt sensitive.
Salt sensitivity is difficult to accurately measure. Additionally, salt sensitivity is not a static variable, and the limit above which people are considered salt sensitive differs depending the definition used.
However, most people who are hypertensive are also salt sensitive, especially when their blood pressure is very high (1).
The physiological mechanisms behind salt sensitivity are incompletely understood. It’s likely that salt sensitivity is caused by abnormalities in the regulation of sodium balance.
One recent study showed that the excretion of excess sodium from the body (in urine) fluctuates according to a 7-day rhythm and is entirely independent of sodium intake (2).
It is possible that disruptions of this natural rhythm may have something to do with salt sensitivity, but further studies are needed.
Bottom Line: Salt sensitivity is a measure of how blood pressure changes in response to the dietary intake of salt (sodium).
Why Is Salt Sensitivity Important?
There is currently no cure for salt sensitivity itself. However, salt-sensitive individuals may need to take anti-hypertensive medication or limit their dietary salt intake.
For those who are salt sensitive, sticking to these recommendations might reduce the risk of hypertension and heart disease (7).
However, some observational studies suggest there is a J-shaped association between salt intake and heart disease. Both too little and too much salt may be harmful (8).
Additionally, meta-analyses of randomized controlled trials suggest that salt restriction causes only a mild reduction in blood pressure, and some even conclude that salt intake does not significantly affect heart disease risk (9, 10).
These findings were based on averages, and the studies didn’t differentiate between salt sensitive and insensitive individuals. Randomized controlled trials comparing salt sensitive and insensitive individuals are needed.
Many observational studies also provide inconsistent results. Individual differences, as well as methodological weaknesses, may be to blame for the controversy.
Bottom Line: Studies on whole populations provide conflicting results regarding the association of salt intake and heart disease risk. However, limiting salt intake is probably important for those who are salt sensitive.
What Causes Salt Sensitivity?
Not everyone is sensitive to salt intake. It depends on the following factors:
- Genes: Salt sensitivity depends on people’s genetics. Multiple genes seem to be involved.
- Race: Black people are more likely to be salt sensitive, compared to white people (11).
- Age: The blood pressure of older people is more likely to respond to changes in salt intake, compared to young people (12).
- Gender: Some studies indicate that women are at a greater risk of being salt sensitive than men, but the evidence is inconsistent (13).
- Hypertension: Those who are hypertensive are more likely to be salt sensitive than people with normal blood pressure (14).
- Low potassium intake: People’s salt sensitivity is greater when their potassium intake is low (15, 16).
Bottom Line: People’s sensitivity to salt intake mainly depends on genetic factors. Old age and low potassium intake may also increase the risk.
Summary and Real-Life Application
This review concluded that a high salt intake may result in elevated blood pressure (hypertension) among those who are salt sensitive.
On the other hand, those who are not salt sensitive do not develop hypertension from eating too much salt, although a very high intake may still be unhealthy.
Salt sensitivity is usually associated with hypertension. If your blood pressure is too high, you may benefit from reducing your intake of salted food.