Disclaimer
Consuming too much salt can cause organ damage and death. This article in no way suggests that eating excessive amounts of salt is a healthy practice.
Commonly Accepted Belief
Consider:
- The opposite of
dark
islight
. - The opposite of
light
isheavy
. - Therefore
dark
means the same asheavy
.
There's obviously something wrong with this logic. Yet that's the same logic used to suggest that salt is unhealthy:
- Hypertension, a disease where one's blood pressure is continuously
higher than normal
, is commonly referred to as high blood pressure. - Consuming salt temporarily makes one's blood pressure
higher than normal
. - Therefore, consuming salt causes hypertension.
Similarly it's the same false logic often used to suggest that low-salt diets are healthy:
- A low-salt diet can reduce the risk of death for some hypertensive people.
- Reducing the risk of death is healthy.
- Therefore, a low-salt diet is healthy.
The Truth
There is a limit to how much pressure the blood system can safely handle. Too much pressure can cause aneurysms or rupture of the aorta, leading to stroke or death. Anyone with hypertension should avoid anything that raises their already high blood pressure as it could push it past their personal limit. For instance, they shouldn't run up stairs, and they shouldn't get angry.
On the other hand, if they can do anything to reduce their normally high blood pressure, they should do so, as it gives them a greater margin for survival when they unavoidably do something that temporarily raises their blood pressure. For instance, walking slowly, remaining calm, and maintaining constant and slightly low levels of sodium by limiting the amount of salt they consume.
For hypertensive people, the benefits of a low-salt diet can sometimes outweigh the risks.
But for non-hypertensive people, a low-salt diet offers risks, but no benefits.
In fact, it isn't the level of sodium in the blood that affects blood pressure, it is changes in the level of sodium that affect it. A sudden increase in blood sodium causes, through osmosis, the body's cells to transfer water from the cells into the blood, thereby increasing blood pressure. After a while, the larger sodium ions, again through osmosis, move into the cells and blood pressure stabilizes.
Similarly, a sudden decrease in blood sodium would cause water to move from the blood into the cells until the cells could release their sodium into the blood to regain equilibrium.
Either way, it isn't the level of sodium in the blood that affects blood pressure, it is the changes in sodium that affect it. For people with normally high levels of sodium, a sudden increase will have far less effect than it will for people with normally low levels of sodium. People with normally low sodium levels are far more sensitive to changes, encouraging the myth that salt causes high blood pressure.
Risks
Low sodium blood levels, known as hyponatremia, can interfere with one's brain processes, causing seizures, comas, and death.
Assuming their physicians have even bothered to tell them about it, hypertensive people willingly risk these effects in order to reduce their risk of stroke or heart attack. But there are times when the risk simply isn't worth it. In periods of excessively hot weather, the people most likely to suffer are those on low-salt diets. All they need to do is add some salt to their glasses of water, but knowing that salt is bad for them, they don't, the low-sodium levels make them confused, they become dehydrated, and they die.
Meanwhile, the vast majority of people do not have chronically high blood pressure. For them, a low-salt diet is unjustifiably dangerous, whatever the weather.
Above minimum and occationally slightly high amounts of dietary salt can be quite beneficial and healthy.