Health organizations have been warning us about the dangers of salt for a long time.
That's because high salt intake has been claimed to cause a number of health problems, including high blood pressure and heart disease.
However, decades of research have failed to provide convincing evidence to support this ().
What's more, many studies actually show that eating too little salt can be harmful.
This article takes a detailed look at salt and its health effects.
Salt is also called sodium chloride (NaCl). It consists of 40% sodium and 60% chloride, by weight.
Salt is by far the biggest dietary source of sodium, and the words "salt" and "sodium" are often used interchangeably.
Some varieties of salt may contain trace amounts of calcium, potassium, iron and zinc. Iodine is often added to table salt (, ).
The essential minerals in salt act as important electrolytes in the body. They help with fluid balance, nerve transmission and muscle function.
Some amount of salt is naturally found in most foods. It's also frequently added to foods in order to improve flavor.
Historically, salt was used to preserve food. High amounts can prevent growth of the bacteria that cause food to go bad.
Salt is harvested in two main ways: from salt mines and by evaporating sea water or other mineral-rich water.
There are actually many types of salt available. Common varieties include plain table salt, Himalayan pink salt and sea salt.
The different types of salt may vary in taste, texture and color. In the picture above, the one on the left is more coarsely ground. The one on the right is finely ground table salt.
In case you're wondering which type is the healthiest, the truth is that they are all quite similar.
Bottom Line: Salt is mainly composed of two minerals, sodium and chloride, which have various functions in the body. It is found naturally in most foods, and is widely used to improve flavor.
Health authorities have been telling us to cut back on sodium for decades. They say you should consume no more than 2,300 mg of sodium per day, preferably less (, , ).
This amounts to about one teaspoon, or 6 grams of salt (it is 40% sodium, so multiply sodium grams by 2.5).
However, about 90% of US adults consume a lot more than that ().
Eating too much salt is claimed to raise blood pressure, thereby increasing the risk of heart disease and stroke.
However, there are some serious doubts about the true benefits of sodium restriction.
It is true that reducing salt intake can lower blood pressure, especially in people with a medical condition called salt-sensitive hypertension ().
But, for healthy individuals, the average reduction is very subtle.
One study from 2013 found that for individuals with normal blood pressure, restricting salt intake reduced systolic blood pressure by only 2.42 mmHg and diastolic blood pressure by only 1.00 mmHg ().
That is like going from 130/75 mmHg to 128/74 mmHg. These are not exactly the impressive results you would hope to get from enduring a tasteless diet.
What's more, some review studies have found no evidence that limiting salt intake will reduce the risk of heart attacks, strokes or death (, ).
Bottom Line: Limiting salt intake does result in a slight reduction in blood pressure. However, there is no strong evidence linking reduced intake to a lower risk of heart attacks, strokes or death.
There is some evidence suggesting that a low-salt diet can be downright harmful.
The negative health effects include:
- Elevated LDL cholesterol and triglycerides: Salt restriction has been linked to elevated LDL (the "bad") cholesterol and triglycerides ().
- Heart disease: Several studies report that less than 3,000 mg of sodium per day is linked to an increased risk of dying from heart disease (, , , ).
- Heart failure: One analysis found that restricting salt intake increased the risk of dying for people with heart failure. The effect was staggering, with a 160% higher risk of death in individuals who reduced their salt intake ().
- Insulin resistance: Some studies have reported that a low-salt diet may increase insulin resistance (, , , ).
- Type 2 diabetes: One study found that in type 2 diabetes patients, less sodium was associated with an increased risk of death ().
Bottom Line: A low-salt diet has been linked to higher LDL and triglyceride levels, and increased insulin resistance. It may increase the risk of death from heart disease, heart failure and type 2 diabetes.
Stomach cancer, also known as gastric cancer, is the fifth most common cancer.
It is the third leading cause of cancer death worldwide, and is responsible for more than 700,000 deaths each year ().
Several observational studies associate high-salt diets with an increased risk of stomach cancer (, , , ).
A massive review article from 2012 looked at data from 7 prospective studies, including a total of 268,718 participants ().
It found that people with high salt intake have a 68% higher risk of stomach cancer, compared to those who have a low intake.
Exactly how or why this happens is not well understood, but several theories exist:
- Growth of bacteria: High salt intake may increase the growth of Helicobacter pylori, a bacteria that can lead to inflammation and gastric ulcers. This may increase the risk of stomach cancer (, , ).
- Damage to stomach lining: A diet high in salt may damage and inflame the stomach lining, thus exposing it to carcinogens (, ).
However, keep in mind that these are observational studies. They can not prove that high salt intake causes stomach cancer, only that the two are strongly associated.
Bottom Line: Several observational studies have linked high salt intake with an increased risk of stomach cancer. This may be caused by several factors.
Most of the salt in the modern diet comes from restaurant foods or packaged, processed foods.
In fact, it is estimated that about 75% of the salt in the US diet comes from processed food. Only 25% of the intake occurs naturally in foods or is added during cooking or at the table ().
Salted snack foods, canned and instant soups, processed meat, pickled foods and soy sauce are examples of high-salt foods.
There are also some seemingly un-salty foods that actually contain surprisingly high amounts of salt, including bread, cottage cheese and some breakfast cereals.
If you are trying to cut back, then food labels almost always list the sodium content.
Bottom Line: Foods that are high in salt include processed foods, such as salted snacks and instant soups. Less obvious foods, such as bread and cottage cheese, may also contain a lot.
Some health conditions make it necessary to cut back on salt. If your doctor wants you to limit your intake, then definitely continue to do so (, ).
However, if you are a healthy person who eats mostly whole, single ingredient foods, then there is probably no need for you to worry about your salt intake.
In this case, you can feel free to add salt during cooking or at the table in order to improve flavor.
Eating extremely high amounts of salt can be harmful, but eating too little may be just as bad for your health ().
As is so often the case in nutrition, the optimal intake is somewhere between the two extremes.