Eating too little sodium can be just as bad as eating too much of it.
by Hrefna Palsdottir, MS
Sodium is an important electrolyte and a main component of table
salt.
Too much sodium has been linked to high blood pressure, and health organizations recommend that we limit our intake (
1,
2,
3).
Most current guidelines recommend eating 2,300 mg per day, or less. Some even go as low as 1500 mg per day (
4).
However, even though
too much sodium causes problems, eating
too little can be just as
bad.
Here are 6 little-known dangers of restricting sodium too much.
1. Possible Increase in Insulin Resistance
A few studies have linked low-sodium diets to increased insulin resistance (
5,
6,
7).
Insulin resistance is when the body’s cells don’t respond well to signals from the hormone
insulin, leading to higher insulin and blood sugar levels.
Insulin resistance is believed to be a major driver of many serious diseases, including type 2 diabetes and heart disease (
8,
9).
One study of 152 healthy people found that insulin resistance increased after only 7 days on a low-sodium diet (
5).
Yet not all studies agree, and some have found no effect, or even a decrease in insulin resistance (
10,
11,
12).
However,
these studies varied in length, study population and degree of salt
restriction, which may explain the differences in results.
Bottom Line:
Low-sodium diets have been associated with increased insulin
resistance, a condition that causes higher blood sugar and insulin
levels. This may lead to type 2 diabetes and other serious diseases.
2. No Clear Benefit for Heart Disease
It is true that reducing sodium can reduce blood pressure.
However, blood pressure is only a risk factor for disease. What we really care about is
hard end-points like heart attacks or death.
Several observational studies have looked at the effects of low-sodium diets on heart attacks, strokes and the risk of death (
13,
14,
15).
One
study found that less than 3,000 mg of sodium per day is linked to an
increased risk of dying from heart disease, including from heart attacks
and strokes (
14).
Disturbingly,
another study reported a higher risk of dying from heart disease at the
low sodium levels that many guidelines currently recommend (
15).
However, other studies have reported conflicting results, so this matter is far from settled (
16,
17,
18).
In
a 2011 review of controlled trials, reducing sodium did not reduce the
risk of dying from heart attacks or strokes, and it increased the risk
of death from heart failure (
19)
Bottom Line:
Although the evidence is mixed, some observational studies show that
low-salt diet are linked to an increased risk of death from heart
attacks or strokes. Controlled trials show no clear benefit.
3. Increased Risk of Death from Heart Failure
Heart failure is when the heart is not able to pump enough blood around the body to meet its needs for blood and oxygen.
This doesn’t mean that your heart stops working completely, but it’s still a very serious health issue.
Interestingly, low-sodium diets have been linked to an increased risk of death in people with heart failure.
One review of controlled trials found that for people with heart failure, limiting sodium intake increased the risk of dying (
19).
In fact, the effect was strong — people who restricted their sodium intake had a
160% higher risk of death. This is concerning, as patients with heart failure are often told to limit their sodium intake.
Yet the results were strongly influenced by only one study, so more research is needed.
Bottom Line:
There is some evidence showing that people with heart failure may have a
higher risk of dying on a low-sodium diet. However, this needs to be
confirmed by more studies.
4. A Low-Sodium Diet May Raise LDL Cholesterol and Triglycerides
Many factors can increase the risk of heart disease, including elevated
LDL cholesterol and
triglycerides.
Some studies have found that low-sodium diets may increase both LDL cholesterol and triglyceride levels.
In
a 2003 review study of healthy people, low-sodium diets caused a 4.6%
increase in LDL cholesterol and a 5.9% increase in triglycerides (
20).
A more recent review reported a 2.5% increase in cholesterol and a 7% increase in triglycerides (
21).
What’s
more, these studies found that salt restriction only caused minor
reductions in blood pressure on average, with a slightly stronger effect
in people with high blood pressure.
Bottom Line:
Studies have found that limiting salt may raise LDL cholesterol and
triglycerides, which are common risk factors for heart disease.
5. Increased Risk of Death for Diabetics
Diabetics have an increased risk of heart attacks and strokes (
22).
Therefore, many guidelines for diabetics recommend limiting salt intake (
23,
24).
However,
some studies have found an association between low sodium intake and an
increased risk of death for both type 1 and type 2 diabetes (
25,
26).
However, these were observational studies, and their results should be interpreted with caution.
Bottom Line:
Patients with type 1 and type 2 diabetes may have an increased risk of
death on a low-sodium diet. However, this needs to be studied further.
6. Higher Risk of Hyponatremia (Low Blood Levels of Sodium)
Hyponatremia is a condition characterized by low levels of sodium in the blood.
Its
symptoms are similar to those caused by dehydration, and in severe
cases the brain may swell and lead to headaches, seizures, coma and even
death (
27).
Certain populations, like older adults, have a higher risk of hyponatremia (
28).
That’s because older adults are more likely to have an illness or take medication that can reduce sodium levels in the blood.
Athletes, especially those who participate in long-distance endurance events, are also at a high risk of developing
exercise-associated hyponatremia (
29,
30).
In their case, it’s usually caused by drinking too much
water and failing to replace the sodium that is lost through sweat (
31).
Bottom Line:
A condition called hyponatremia, or low blood sodium levels, may affect
certain people like older adults and some athletes. Eating less salt
raises the risk of this condition.
How Much Sodium Should You Eat?
Studies suggest that there is a J-shaped curve when it comes to the effects of sodium.
Too much may be harmful, but too little can also have serious consequences.
The lowest risk of health issues and death seems to be somewhere in between.
An intake of
3000–5000 milligrams per day has been suggested as optimal, which is similar to what the average person already eats, or 3371 mg per day (
32,
33).
This
amounts to 7.5-12.5 grams of table salt per day, which equals 1.5-2.5
teaspoons per day (salt is only 40% sodium, so multiply sodium by 2.5 to
find the amount of salt).
However, some people may benefit from restricted sodium intake, such as those with salt-sensitive high blood pressure (
34).
If
you have a medical condition that requires a diet low in sodium, or if
your doctor has advised you to limit your intake, then by all means
continue to do so.
But if you are a healthy person trying to stay
healthy, then there is no good evidence that following a low-sodium diet
will improve your health.
Most of the excess sodium people eat comes from
processed, packaged foods – stuff you shouldn’t be eating much of anyway.
Adding some salt to your
healthy foods to improve flavor is both safe and healthy, and can make your diet much more pleasurable.
