NaCl, or popularly known as salt, is a compound found in almost everything we consume – from food to drinks. For decades, it has been considered one of the main reasons for the development of high blood pressure (hypertension) – a phenomenon that is chronically extremely harmful to the human body. Therefore, several leading health institutions have issued guidelines over the years to limit sodium/salt intake in our diet.
However, these guidelines are considered controversial – it has been proven that not everyone benefits from reducing salt intake, while at the same time it ignores the impact of other nutrients on blood pressure.
Therefore, if we want to talk about salt intake and its impact on blood pressure, we cannot ignore the importance of potassium intake. Sodium, chlorides and potassium are so closely related to each other that, in order for the story to make sense, we have to look at them together as a single unit.
Simply put, we can look at these three minerals as “friends”, where each of them plays a unique role. Chloride follows sodium wherever it goes and never leaves it. Sodium and potassium chase each other, but constantly and endlessly actually just pass each other in an elusive dance. Potassium is most often found inside and sodium outside the cell. When sodium “chases” potassium and enters the cell, potassium leaves. When sodium “buses” back home towards the outside of the station, potassium goes inside on a parallel “bus”.
This “bus”, in technical jargon known as the “sodium-potassium pump”, and at rest consumes about 20-40% of our energy or TDEE, and serves to keep sodium (and the chloride that always follows it) primarily outside the cell, and potassium primarily inside the cell. This separation of salt and potassium is crucial for all their functions within the body, listed below.
Despite its continued demonization and accusations of negative health effects, sodium, and by extension salt, is an essential nutrient required to maintain optimal human health.
Salt and potassium are electrolytes and serve to hydrate. Since they are water soluble, water loss through sweating, vomiting, diarrhea or excessive urination leads to their loss
Because of its function in transport, salt is extremely important for digestion and the digestive tract – from the release of saliva, stomach acid and bile acids, to the direct absorption of glucose, amino acids and many vitamins and minerals: Vitamin C, Vitamin B5, Biotin (vitamin B7), Sulfates, Selenium, Phosphorus, Magnesium, Iodine
Once we manage to absorb nutrients, salt is involved in nutrient retention (prevents nutrient excretion in urine), their transport into cells and between tissues, and in the transport of many other essential substances, such as numerous hormones and creatine.
Salt and chlorides are used as one of the main ways of controlling acidity in the body as a whole, but also in individual tissues and cellular components (more precisely pH control).
Salt and potassium enable neurons to react to neurotransmitters or other signals and further transmit signals to other neurons or muscle cells.
Salt and potassium “neutralize” neurotransmitters, preventing them from having a greater effect than intended. A lack of these minerals in the brain could contribute to glutamate sensitivity.
Potassium activates numerous enzymes involved in energy metabolism, antioxidant system and cell repair.
Although the evidence is weaker than for blood pressure, a balanced intake of salt and potassium appears to be very important for bone and kidney health.
History of salt and potassium intake
Researchers studying the diet of ancient hunter-gatherers suggest that our distant ancestors consumed about 700 milligrams of sodium per day, mostly from meat, and 11 grams of potassium per day (or 11,000 mg/d), mostly from plant sources, although raw red meat also contains solid quantities.
In contrast, we modern humans eat an average of 2.3-6.9 g/d of sodium and 3.2 g/d of potassium.
Since our ancient ancestors consumed much more potassium than we do today, but far less sodium, they would always lack an adequate amount of sodium. A craving for salt would have driven them to seek out more salty foods, salt deposits, or ocean water that could be used to produce salt. Over time, people became more and more productive and made it easier to find adequate amounts of salt. What was once a craving that pushed us to actively seek and work for salt, today has become a simple addition of salt to all the food we consume.
In the meantime, we have also “succeeded” in producing plant-based foods that are high in calories and low in potassium. Cereals, which we consume in much larger quantities today, contain little potassium compared to tubers such as potatoes, legumes (beans, lentils and peas), fruits and vegetables.
In the last century, we moved to a huge extent to the production of processed, prepackaged food, and about 70% of the sodium in our diet comes from hidden salt that is added to such foods, and serves primarily as a preservative, in order to improve texture or taste. Most of such sodium is incorporated into food so that it affects the texture of the product, but it is “hidden” from our taste buds, so we don't even notice its intake.
Effect on blood pressure
Sodium has long been known to increase blood pressure – especially in people who already have elevated levels. In the late 1940s, this connection became widely recognized, and since then research has established a strong link between excessive sodium intake and elevated blood pressure.
One of the largest studies on this topic is the “Prospective Urban Rural Epidemiology trial” or PURE for short. Analyzing the sodium levels in the urine of more than 100,000 people from 18 countries on five continents, researchers found a strong positive relationship between higher sodium intake and significantly increased blood pressure.
Where did that link come from?
If you consume too much salt and not enough potassium, water will reach your blood and other extracellular fluids, but the cells will remain dehydrated because there is not enough potassium to “draw” the water inside the cell.
Potassium is also needed to get rid of excess salt by increasing its excretion in the urine. Without potassium, salt builds up in your blood, causing the water content of your blood to increase. As the water content in your blood increases, it puts more and more pressure on the walls of your blood vessels, causing increased blood pressure. Furthermore, the extracellular fluid in such a situation could accumulate in your face, arms, legs or almost any part of your body and lead to swelling, i.e. feeling of swelling.
Such an increase in blood pressure in long-term episodes significantly increases the risk of cardiovascular diseases such as heart attack and stroke and kidney disease. Consuming an adequate amount of potassium would help remove salt from your body without raising your blood pressure and without increasing your risk of chronic disease.
In order to keep blood pressure stable and to reduce the possibility of swelling, salt and potassium intake must be balanced.
This is one of the possible reasons for the well-established phenomenon: salt intake does not affect all people equally. Certain individuals are sensitive to salt intake, while others can consume large amounts without the salt significantly affecting their blood pressure.
In addition to the basal intake of potassium, it has been observed that people with high blood pressure, diabetes and chronic kidney disease, as well as older adults, but also African-Americans (influence of genetics), are more sensitive to the effect of salt.
There are several reasons that lead us to conclude that the ratio of salt and potassium intake is more important than the absolute amount of either, or at least that their balanced intake is as important as getting a certain amount of either:
• Potassium “neutralizes” the increase in blood pressure caused by salt.
• Potassium reduces the loss of calcium in the urine, which salt can cause
• Together they participate in numerous processes and each one is needed to get rid of the excess of the other.
This does not necessarily mean that we need the exact ratio. It is very likely that we need a certain level of potassium in order to tolerate a certain range of sodium intake and vice versa
However, official recommendations for salt and potassium intake are treated separately.
Input recommendations
The National Academy of Medicine recently (2019) revised the Adequate Intakes (AI) for salt and potassium:
Potassium
The Adequate Intake (AI) for potassium is set at 2300 mg/d for adult women, 3400 mg/d for adult men.
Our recommendation for potassium intake is that the AI is considered the minimum goal, and the optimal intake ranges from 4700-11,000 mg/d for both sexes.
Sodium
The Academy has set the appropriate sodium intake at 1,500 mg/d and the chronic risk reduction intake at 2,300 mg/d or less. (In the recommendations, we are talking about sodium, not salt. We get the amount of salt when we multiply the amount of sodium by a factor of 2.5).
It's very important to note, because people often forget or don't read the guidelines thoroughly enough, that these sodium intake recommendations only apply to people who aren't sweating as a result of heat or high-intensity activity and don't take into account the need for sodium and potassium balance.
Conclusion
If you consume potassium in the optimal range above, you should add salt to your food “to taste” and you can probably eat as much salt as you like without negative effects on your health. If you consume potassium near the Minimum Intake (AI), you may need to reduce your sodium intake to between 1500 and 2300 mg/day if you find that higher sodium (salt) intake is causing your blood pressure to rise.
People with high blood pressure who consume more than 7 grams of sodium per day should reduce their intake to the AI level for sodium intake, unless they sweat excessively and/or live in humid environments and/or engage in vigorous physical activity. However, reducing sodium intake for “healthy individuals” and/or those with adequate potassium intake does not seem to make much of a difference.
Although the health authorities still advocate a lower sodium intake, our recommendation is that, if you do not have any of the listed chronic health problems, place much greater emphasis on adequate potassium intake!
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